ISSN 131A-D2D7 Pages 213-416 ■ Year 2016, Vol. 63, No. 2 ActaChimica Sic Acta Chimica Sic Slovenica ActaC 63/2016 Selected Titles: Indoor Nanoparticles Measurements in Workplace Environment: The Case of Printing and Photocopy Center ■ Study of the Influence of Key Process Parameters on Furfural Production I Effect of Process Parameters on the Physicochemical Properties of Nano- and Micrometric Zinc Oxide ■ Stereoselective Synthesis of Southern Fragment of Hantupeptin-A ■ Experimental and Computational Study of the Thermodynamic Properties of Trivalent Cobalt Schiff Base Complexes with Cyclic Amines http://acta.chem-soc.si 9771318020004 EDITOR-IN-CHIEF ALEKSANDER PAVKO Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia E-mail: ACSi@fkkt.uni-lj.si, Telephone: (+386)-1-479-8578; Fax: (+386)-1-241-9144 ASSOCIATE EDITORS Marija Bešter-Rogač, University of Ljubljana, Slovenia Janez Cerkovnik, University of Ljubljana, Slovenia Krištof Kranjc, University of Ljubljana, Slovenia Franc Perdih, University of Ljubljana, Slovenia Helena Prosen, University of Ljubljana, Slovenia Damjana Rozman, University of Ljubljana, Slovenia Melita Tramšek, Jožef Stefan Institute, Slovenia Irena Vovk, National Institute of Chemistry, Slovenia ADMINISTRATIVE ASSISTANT Marjana Gantar National Institute of Chemistry, Slovenia EDITORIAL BOARD Wolfgang Buchberger, Johannes Kepler University, Austria Alojz Demšar, University of Ljubljana, Slovenia Stanislav Gobec, University of Ljubljana, Slovenia Marko Goličnik, University of Ljubljana, Slovenia Günter Grampp, Graz University of Technology, Austria Wojciech Grochala, University of Warsaw, Poland Danijel Kikelj, Faculty of Pharmacy, Slovenia Ksenija Kogej, University of Ljubljana, Slovenia Janez Košmrlj, University of Ljubljana, Slovenia Blaž Likozar, National Institute of Chemistry, Slovenia Mahesh K. Lakshman, The City College and The City University of New York, USA Janez Mavri, National Institute of Chemistry, Slovenia Friedrich Srienc, University of Minnesota, USA Walter Steiner, Graz University of Technology, Austria Jurij Svete, University of Ljubljana, Slovenia Ivan Švancara, University of Pardubice, Czech Republic Jiri Pinkas, Masaryk University Brno, Czech Republic Gašper Tavčar, Jožef Stefan Institute, Slovenia Christine Wandrey, EPFL Lausanne, Switzerland Ennio Zangrando, University of Trieste, Italy, Chairman Branko Stanovnik, Slovenia Members Josef Barthel, Germany Udo A. Th. Brinkman, The Netherlands Attilio Cesaro, Italy Dusan Hadzi, Slovenia Vida Hudnik, Slovenia Venceslav Kaucic, Slovenia ADVISORY EDITORIAL BOARD Željko Knez, Slovenia Radovan Komel, Slovenia Janez Levec, Slovenia Stane Pejovnik, Slovenia Anton Perdih, Slovenia Slavko Pečar, Slovenia Andrej Petrič, Slovenia Boris Pihlar, Slovenia Milan Randic, Des Moines, USA Jože Škerjanc, Slovenia Miha Tišler, Slovenia Burda Vasic-Rački, Croatia Marjan Veber, Slovenia Gorazd Vesnaver, Slovenia Jure Zupan, Slovenia Boris Žemva, Slovenia Majda Žigon, Slovenia Acta Chimica Slovenica is indexed in: Chemical Abstracts Plus, Current Contents (Physical, Chemical and Earth Sciences), PubMed, Science Citation Index Expanded and Scopus. Impact factor for 2013 is IF = 0,69. Izdaja - Published by: SLOVENSKO KEMIJSKO DRUŠTVO - SLOVENIAN CHEMICAL SOCIETY - Slovenian Chemical Society Naslov redakcije in uprave - Address of the Editorial Board and Administration Hajdrihova 19, SI-1000 Ljubljana, Slovenija Tel.: (+386)-1-476-0252; Fax: (+386)-1-476-0300; E-mail: chem.soc@ki.si Sloven <) Izdajanje sofinancirajo - Financially supported by: Slovenian Research Agency, Ljubljana, Slovenia National Institute of Chemistry, Ljubljana, Slovenia Jožef Stefan Institute, Ljubljana, Slovenia Faculty of Chemistry and Chemical Technology at University of Ljubljana, Slovenia Faculty of Chemistry and Chemical Engineering at University of Maribor, Slovenia Faculty of Pharmacy at University of Ljubljana, Slovenia University of Nova Gorica, Nova Gorica, Slovenia Chamber of Commerce and Industry of Slovenia - Chemical and Rubber Industry Association, Slovenia Članom je revija na voljo brezplačno. Za nečlane in pravne osebe znaša letna naročnina 50 EUR, za inozemstvo 110 EUR vključno s poštnino. Annual subscription: 110 EUR including postage. Transakcijski račun: 02053-0013322846 Bank Account No.: SI56020530013322846-Nova Ljubljanska banka d. d., Trg republike 2, SI-1520 Ljubljana, Slovenia, SWIFT Code: LJBA SI 2X Na podlagi Zakona o davku na dodano vrednost sodi revija Acta Chimica Slovenica med proizvode, od katerih se obračunava DDV po stopnji 9,5 %. Acta Chimica Slovenica izhaja štirikrat letno v 200 izvodih - Acta Chimica Slovenica appears quarterly in 200 copies Oblikovanje ovitka - Design cover: KULT, oblikovalski studio, Simon KAJTNA, s. p. Grafična priprava za tisk: Majanafin, d. o. o. Tisk - Printed by: Tiskarna Skušek, Ljubljana © Copyright by Slovenian Chemical Society Graphical Contents ActaChimicaSlc ActaChimicaSlc Slovenica ActaC Year 2016, Vcl. 63, Nc. 2 SCIENTIFIC PAPER 213—219 Analytical chemistry Total Phenolics, Total Anthocyanins, Antioxidant and Pro-oxidant Activity of Some Red Fruits Teas Bianca Moldovan, Anamaria Hosu, Luminita David and Claudia Cimpoiu 220-226 Analytical chemistry Rapid Electrochemical Method for the Determination of L-DOPA in Extract From the Seeds of Mucuna Prurita Dalibor M. Stankovi}, Anchalee Samphao, Biljana Dojcinovi} and Kurt Kalcher 227-240 Organic chemistry New Approaches for the Synthesis, Cytotoxicity and Toxicity of Heterocyclic Compounds Derived from 2-Cyanomethylbenzo[c]imidazole Rafat M. Mohareb, Abeer A. Mohamed and Amira E. M. Abdallah Graphical Contents 241-250 Physical chemistry DFT Studies of NH-C1 Hydrogen Bond of Amino Acid Hydrochloride Salts in Ion Channels Marjan Moridi, Setareh Shekarsaraei and Nasser L. Hadipour it X1 - il' Co/'O^ M2JUH/ I Ctftty JOflUHi KtfCH&NHi ft & Jf ^O ■ J?** i Cj'i^tuyKj 251—257 Physical chemistry Catalytic Alkylation of Acetone with Ethanol Over Pd/carbon Catalysts in Flow-through System Via Borrowing Hydrogen Route Gyula Novodarszki, György Onyestyak, Agnes Farkas Wellisch and Aranka Pilbath 258—262 Physical chemistry The Octyltrimethylamonium Bromide Adsorption at the Mercury Electrode / NaClO4 Solution Interface Dorota Gugala-Fekner, Jolanta Nieszporek and Dorota Sienko 263—270 Organic chemistry 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: As an Effective, New and Reusable Media for the Synthesis of 14-Aryl-14H-dibenzo[«l/]xanthenes Leila Zare Fekri and Hajar Saeedi Fard 271-278 Physical chemistry Substitution Reactions of the Aluminum Chlorogermylenoid ^GeClAlC^ with HF, H2O, NH3, HC1, H2S, and PH3 Bingfei Yan, Mingxia Zhang, Wenzuo Li,* Cuiping Xiao, Qingzhong Li and Jianbo Cheng Graphical Contents 279—286 Inorganic chemistry Synthesis, Characterization and X-Ray Crystal Structures of ds-Dioxomolybdenum(VI) Complexes of Similar Tridentate Aroylhydrazone Schiff Bases with Catalytic Epoxidation Activity Qing Liu, Jiahui Lin, Juan Liu, Wu Chen and Yongming Cui 287—297 Analytical chemistry Solid-liquid Extraction of Phenolics from Red Grape Skins Ivana Tomaz, Luna Maslov, Domagoj Stupic, Darko Preiner, Danijela Asperger, and Jasminka Karoglan Kontic 298—308 Chemical, biochemical and environmental engineering Study of the Influence of Key Process Parameters on Furfural Production Ljudmila Fele Žilnik, Viktor Grilc, Ivan Mirt and Željko Cerovečki 309—316 Inorganic chemistry H3PW12O40 Encapsulation by Nanoporous Metal Organic Framework HKUST-1: Synthesis, Characterization, Activity and Stability Ezzat Rafiee and Narges Nobakht 317—322 Inorganic chemistry Effect of Process Parameters on the Size and Shape of Nano- and Micrometric Zinc Oxide Jolanta Pulit-Prociak, and Marcin Banach Graphical Contents 279—286 Inorganic chemistry New Iridium Complex Coordinated with Tetrathiafulvalene Substituted Triazole-pyridine Ligand: Synthesis, Photophysical and Electrochemical Properties Zhi-Gang Niu, Hui Xie, Li-Rong He, Kai-Xiu Li, Qing Xia, Dong-Min Wu, Gao-Nan Li 327—334 Chemical, biochemical and environmental engineering Indoor Nanoparticles Measurements in Workplace Environment: The Case of Printing and Photocopy Center Irena Grgic, Jožica Bratec and Marija Bester Rogač 335-343 Materials science Characterization of Cobalt Oxide Nanoparticles Prepared by the Thermal Decomposition of [Co(NH3)5(H2O)](NO3)3 Complex and Study of Their Photocatalytic Activity Saeed Farhadi, Masoumeh Javanmard and Gholamali Nadri 344-350 Organic chemistry Stereoselective Synthesis of Southern Fragment of Hantupeptin A Avula Srinivas, Malladi Sunitha and Chakunta Govind Ra 351—362 Inorganic chemistry Experimental and Computational Study of the Thermodynamic Properties of Trivalent Cobalt Schiff Base Complexes with Cyclic Amines Sheida Esmaielzadeh, Leila Azimian and Zohreh Zare Graphical Contents 363-368 Materials science On Eccentric Connectivity Index of TiO2 Nanotubes Imran Nadeem and Hani Shaker 369—375 Inorganic chemistry Oxidation of Ruthenium and Iridium Metal by XeF2 and Crystal Structure Determination of [Xe-FJRuFJ'XeF. and [Xe.FJMFJ (M = Ru, Ir) Melita Tramšek, Evgeny Goreshnik and Gašper Tavčar 376—379 General chemistry The Eccentricity Version of Atom-Bond Connectivity Index of Linear Polycene Parallelogram Benzenoid ABC5(P(n,n)) Wei Gao, Mohammad Reza Farahani and Muhammad Kamran Jamil Aniona lopoJojtrcal descriptors. connectivity indices are very ioijMCttnt aitd they have a pionnnent role t» cliemisliy. The alom-boud connectivity iudex of a coamecled graph G is defined a* ABCtGi- v -J, where cf, 95%. In order to classify the teas based on the obtained experimental data the principal component analysis (PCA) was performed. 2. 5. 3. Antioxidant Activity (AA) The antioxidant activity was determined by the ABTS assay according to the method of Re et al.17 with 3. Results and Discussions All the experimental results are presented in Table 2. Moldovan et al.: Total Phenolics, Total Anthocyanins, Antioxidant ... 216 Acta Chim. Slov. 2015, 62, 213-219 Table 2. The total phenolic content (TPC - mg GAE/g fruit tea), total anthocyanins content (TAC - mg Cy-3-gly/g fruit tea), antioxidant activity (AA- mg AAE/g fruit tea), IC50 (mg/mL), pro-oxidant activity (mg/mL) and Pro-Antidex of the analyzed teas (n = 9). No.(producer) TPC TAC AA IC50 Pro-ox Pro-Antidex 1 (A) 15.84 ± 0.15 4.49 ± 0.20 12.95 ± 1.62 1.21 ± 0.01 6.12 ± 0.04 5.06 ± 0.01 2 (B) 12.53 ± 0.15 3.65 ± 0.09 15.19 ± 2.50 2.18 ± 0.07 9.79 ± 0.08 4.48 ± 0.01 3 (A) 23.23 ± 0.42 5.57 ± 0.37 18.27 ± 0.17 0.99 ± 0.01 5.34 ± 0.04 5.40 ± 0.00 4 (B) 13.89 ± 0.20 4.39 ± 0.21 12.96 ± 1.62 1.31 ± 0.02 9.50 ± 0.06 7.35 ± 0.05 5 (A) 18.61 ± 0.22 5.26 ± 0.01 15.41 ± 0.33 0.93 ± 0.00 6.08 ± 0.03 6.55 ± 0.02 6 (B) 28.18 ± 0.40 2.84 ± 0.12 10.96 ± 0.30 1.40 ± 0.02 8.02 ± 0.05 5.71 ± 0.02 7 (B) 15.54 ± 0.07 4.58 ± 0.46 13.13 ± 1.96 1.79 ± 0.02 8.69 ± 0.06 4.85 ± 0.03 8 (C) 29.33 ± 0.20 4.16 ± 0.09 19.02 ± 0.22 0.86 ± 0.04 3.91 ± 0.03 4.54 ± 0.02 9 (A) 18.22 ± 0.11 5.14 ± 0.08 13.42 ± 0.30 1.13 ± 0.01 5.89 ± 0.05 5.23 ± 0.02 10 (A) 16.36 ± 0.46 2.62 ± 0.34 11.24 ± 0.04 1.30 ± 0.03 5.66 ± 0.04 4.35 ± 0.04 11 (B) 13.28 ± 0.17 3.61 ± 0.21 10.87 ± 2.51 3.06 ± 0.01 10.00 ± 0.05 3.28 ± 0.01 12 (C) 14.13 ± 0.13 4.04 ± 0.33 19.06 ± 1.96 0.88 ± 0.03 4.03 ± 0.19 4.58 ± 0.05 3. 1. Total Phenolic Content (TPC) The TPC of the investigated tea extracts was evaluated based on their reduction properties and was determined by Folin-Ciocalteu method (Table 2). The highest TPC of teas from producer A was found for the blueberry tea (23.23 ± 0.42mg GAE/g fruit tea), the lowest value being exhibited by the raspberry tea (15.84 ± 0.15 mg GAE/g fruit tea). There is a 1.4-fold difference between the lowest and the highest TPC values of the investigated teas of this producer. Regarding the teas made by producer B, the TPC was found to be higher in rose hip infusion (28.18 ± 0.40mg GAE/g fruit tea) while the lowest value was obtained for the raspberry tea (12.53 ± 0.15 mg GAE/g fruit tea). There is a 2.2-fold difference between the highest and the lowest TPC values of the teas. The highest TPC value of all investigated teas was found for the strawberry tea from the teas made by producer C, probably due to its high content of hibiscus and rose hip fruit (as labelled by producer). The TPC of the investigated teas varied widely especially from one tea producer to the other. Differences were also observed among teas from the same producer due to different fruit ingredients in each tea. The determined TPC values from 12.53 to 29.33 mg GAE/g fruit tea (126.07 to 295.02 mg GAE/L infusion) are in agreement with 323.4-1549.1 mg GAE/L infusion reported for two times more concentrated infusions (2 g tea/100 mL water) prepared from similar fruit teas.5 As expected, these values are much lower as the TPC of the fruit juices - blueberry 179.5; strawberry 1302; blackcurrant 1919 mg GAE/L,20 due to the fact that fruit tea manufacturing involves processing procedures (such as drying, grinding) that may determine the degradation of the phenolic compounds. 3. 2. Total Anthocyanins Content (TAC) The TAC of the fruit tea infusions was investigated using the pH differential method. The anthocyanins levels were similar in all fruit infusions from producer A (in the range of 4.49-5.57 mg Cy-3-glu/g fruit tea), except for wild berry tea no. 10, which had the lowest TAC (2.62 ± 0.34mg Cy-3-glu/g fruit tea). Furthermore, a statistically significant correlation was found between the TAC and the TPC (r = 0.9068 and p = 0.093). For producer B, except the rose hip tea no. 6 (2.84 ± 0.12mg Cy-3-glu/g fruit tea), similar TAC values were found for the investigated fruit infusions (in the range of 3.61-4.58 mg Cy-3-glu/g fruit tea). As in the previous case, the TAC values followed the same trend as the TPC values, being statistically correlated (r = 0.8775 and p = 0.12). The determined TAC values for the fruit tea infusions of producer C are almost the same (~4 mg Cy-3-glu/g fruit tea). The lowest TAC was found for the rose-hip fruit tea no. 6 (producer B), being 1.85 fold lower as the TAC determined for the rose-hip fruit tea no. 5 (producer A). By comparing these values, it is important to take into account the fruit composition of analysed teas (Table 1). This result may be due to the fact that tea no. 6 contains a lower quantity of blackcurrant (berries that have higher TAC than rose-hip fruits) compared to the tea no.5. This difference may also explain the lower than expected TPC value determined for tea no. 5. Since there is no published report about the TAC of infusions prepared from bagged fruit teas, we can only compare our data with those reported for the TAC of juices prepared from the same fruits as our tea samples. It was reported that blueberry and strawberry juices contain 424.1 to 518.2 mg Cy-3-glu/L,21 and 55.7 mg Cy-3-glu/L,22 respectively. Also, blackberry and cherry fruits contain 198.25 mg Cy-3-glu ■ 100 g-1 fresh matter, and 44.19 mg Cy-3-glu ■ 100 g-1 fresh matter.23 As expected, the TAC of the investigated teas (in the range 26.4-56.06 mg Cy-3-glu/L tea extract) was much lower. 3. 3. Antioxidant Activity (AA) Antioxidant activities of all 12 fruit tea infusions were determined using the ABTS assay, which is based on Moldovan et al.: Total Phenolics, Total Anthocyanins, Antioxidant ... 217 Acta Chim. Slov. 2015, 62, 213-219 the ability of antioxidants to perform as free radical scavengers.24 Significant differences were observed among various tea infusions. The highest ABTS radical cation scavenging activity was exhibited by the blueberry tea of producer A (18.27 ± 0.17mg AAE/g fruit tea) and by the raspberry tea (15.19 ± 2.50 mg AAE/g fruit tea) of producer B, respectively. The lowest AA values were determined for the wild berry tea no. 10 of producer A (11.24 ± 0.04mg AAE/g fruit tea) and for the wild berry tea no. 11 (10.87 ± 2.51mg AAE/g fruit tea) of producer B. There is a 1.4-fold difference between the lowest and the highest AA values of the investigated teas of producer A, the same as for the TPC values. A statistically significant relationship between TPC and AA was observed (r = 0.9529 and p = 0.046), indicating that the concentration of phenolic compound may be a good indicator of the AA of the investigated fruit tea infusions. Surprisingly, no correlation between TPC and AA was observed in teas of producer B. The determined AA for the fruit tea infusions from producer C was almost the same (~19 mg AAE/g fruit tea), and was the highest of the all investigated teas. As expected, the studied tea infusions exhibit a significantly lower AA (in the range of 10.9-15.4 mg AAE/100 mL infusion) compared to conventional teas of Camelia Sinensis (L.) (106 mg AAE/100 mL - black tea, 131 mg AAE/100 mL - green tea, 83 mg AAE/100 mL -oolong tea25). 3. 4. Pro-oxidant Activity The method applied for the evaluation of pro-oxi-dant activity of studied tea infusions is based on their reducing power of iron ion in a Fenton reaction.11 The pro-oxidant activities calculated at an absorbance set at an arbitrary value of 1.000 are reported in Table 2. Significant differences were observed among the pro-oxidant activities of the investigated fruit teas. The highest pro-oxidant activity was exhibited by the raspberry tea of producer A (6.12 ± 0.04 mg/mL) and by the wild berry tea of producer B (10.00 ± 0.05 mg/mL). The lowest pro-oxidant activities were found for both tea from producer C, 3.909 ± 0.028 mg/mL for the strawberry and wild strawberry tea, and 4.03 ± 0.12 mg/mL for wild berry tea, respectively. The results also indicate that the pro-oxidant activity of each type of tea from the producer B was higher than those of the corresponding tea from the producer A, differences being between 1.3-fold (rose-hip teas) and 1.8-fold (blueberry teas). Moreover, it could be observed that the pro-oxidant activity of teas from the producer B are higher than those from the producer C by more than 2.2-fold (e.g. 10.00 vs 4.03 for wildberry tea). Considering the scavenging activity of teas expressed as IC50, the Pro-Antidex values were calculated. This index offer a useful information on the real antioxidant capacity of fruit tea extracts. A lower value of Pro-Antidex indicates that the sample possess a lower pro-oxidant activity.11 Therefore, it would be expected that the tea will be more efficient in neutralizing free radicals. The results indicate that among the teas of producer A the wild berry tea infusion (tea no. 10) has the lowest Pro-Antidex value (4.35 ± 0.04). From the teas of producer B, tea no. 11 (wild berry tea) possess the lowest Pro-Antidex value (3.28 ± 0.01). Comparing the Pro-Antidex values for teas of producer C, it could be observed that the strawberry and wild strawberry tea has a lowest index value (4.54 ± 0.02). Considering all twelve samples, the results show that the blueberry tea from the producer B has the highest Pro-Antidex value (7.35 ± 0.05). The correlation between pro-oxidant activity and antioxidant activity (Figure 1) was acceptable (AA versus Pro-ox - r = 0.6374 and IC50 versus Pro-ox - r = 0.8023), but it would be better to take into account both free radical scavenging activity and pro-oxidant activity for the evaluation of the real antioxidant activity of the fruit teas. The classification was accomplished by principal component analysis, which combined the experimental a) - b) 4 <53 <3> ¡20 o> R2 = 0,4065 ■ ■ 3 R* = 0.6437 ■ $15 O) £ £10 > O CO f 5 CO i ■■ ■ ■ ■ 1C50 (mg/mL) 2 1 g f 0 < 0 0 5 10 15 Pro-oxidant activity (mg/mL) 0 5 10 Pro-oxidant activity (mg/mL) 15 Figure 1.The correlation between Pro-oxidant activity and antioxidant activity (a), respectively Pro-oxidant activity and IC50 (b). Moldovan et al.: Total Phenolics, Total Anthocyanins, Antioxidant ... 218 Acta Chim. Slov. 2015, 62, 213-219 -3 -2 -1 0 Factor 1:48 55% Figure 2. PC1-PC2 scores plot obtained using the TPC, TAC, AA, IC50, Pro-ox and Pro-Antidex values. results into a data matrix highlighting the similarities and differences of teas. On the PC1-PC2 scores plot (Figure 2) four clusters related to the tea producers are observed. Thus, the cluster containing the teas no.1, 3, 5 and 9 represents the producer A, while the cluster including the teas no.2, 4, 6 and 7 corresponds to producer B. The third cluster encloses the teas no.8 and 12 made by producer C. Tea no. 10 (producer A) and tea no. 11 (producer B) are excepted from this classification being grouped in a separate cluster. This behaviour may be due to the fact that these teas are mixtures of pieces of fruits, while the others are bagged teas. 4. Conclusions This paper reports key information on the total phenolic and anthocyanin content, the antioxidant and pro-oxidant properties of different commercially available fruit teas. The investigated teas exhibited different TPC, TAC, AA, Pro-ox and Pro-Antidex values, which varied widely with their composition. The statistical analysis confirms that the characteristics of teas differ significantly depending on the producer. The TAC, TPC and AA of studied teas decreases in the order: blueberry > wild berry > raspberry > strawberry. Since the determination of the antioxidant and pro- oxidant activity of fruit teas do not provide enough information regarding their net free radical scavenging ability, the Pro-Antidex values should be taken into account. Even if the level of biologically active compounds is lower than in black, green or white teas, fruit teas still remain an important source of antioxidants to human diet. 5. Acknowledgments This research is supported by Executive Unit for Financing Education Higher, Research Development and Innovation, project number PN-II-PT-PCCA-2011-3-1-0914. 6. References 1. Konczak-Islam, M. Yoshimoto, D. X. Hou, N. Terahara, O. Yamakawa, J. Agric. Food Chem. 2003, 51, 5916-5922. http://dx.doi.org/10.1021/jf030066o 2. F. C. Stintzing, R. Carle, Trends Food Sci. Tech. 2004, 15, 19-38. http://dx.doi.org/10.1016Zj.tifs.2003.07.004 3. I. Ignat, I. Volf, V. I. Popa, Food Chem. 2011, 126, 18211835. http://dx.doi.org/10.1016/j.foodchem.2010.12.026 4. J. Kristl, A. U. Krajnc, B. Kramberger, S. G. Mlakar, Acta Chim. Slov. 2013, 60, 19-25. 5. A. Belscak, N. Bukovac, J. Piljac-Zegarac, J. Food Bioc-hem.2011, 35, 195-212. http://dx.doi.org/10.1111/j.1745-4514.2010.00375.x Moldovan et al.: Total Phenolics, Total Anthocyanins, Antioxidant ... 219 Acta Chim. Slov. 2015, 62, 213-219 6. B. Tian, Y. Hu, Food Chem. 2005, 91, 413-418. http://dx.doi.Org/10.1016/j.foodchem.2004.06.018 7. L. T. Ling, U. D. Palanisamy, H. M. Cheng, Molecules 2010, 15, 7884-7892. http://dx.doi.org/10.3390/molecules15117884 8. M. Polovka, V. Brezova, A. Stasko, Biophys. Chem.2003, 106, 39-56. http://dx.doi.org/10.1016/S0301-4622(03)00159-5 9. K. Savikin, G. Zdunic, T. Jankovic, D. Godevac, T. Stanojko-vic, D. Pljevljakusic, Food Res. Int. 2014, 62, 677-683. http://dx.doi.org/10.1016Zj.foodres.2014.04.017 10. L. David, A. Hosu, B. Moldovan, C. Cimpoiu, J. Liq. Chro-matogr. Rel. Technol. 2014, 37, 1644-1653. http://dx.doi.org/10.1080/10826076.2013.803206 11. V. L. Singleton, R. Orthofer, R. M. Lamuela-Raventos, in: L. Packer (Ed.): Methods in Enzymology, Academic Press, San Diego, USA, 1999, Vol. 299. 12. M. M. Giusti, R. E. Wrolstad, Curr. Protocols Food Anal. Chem.2001, F1.2:1-13. 13. R. Re, N. Pellegrini, A. Proteggente, A. Pannala, M. Yang, C. Rice-Evans, Free Radical Bio. Med, 1999, 26, 1231-1237. http://dx.doi.org/10.1016/S0891-5849(98)00315-3 14. B. Moldovan, O. Ghic, L. David, C. Chisbora, Rev. Chim. (Bucharest), 2012, 63, 463-464. 15. L. T. Ling, S. A. Yap, A. K. Radhakrishnan, T. Subramaniam, H. M. Cheng, U. D. Palanisamy, Food Chem. 2009, 113, 1154-1159. http://dx.doi.org/10.1016/j.foodchem.2008.09.004 16. S. Hakkinen, M. Heinonen, S. Karenlampi, H. Mykkanen, J. Ruuskanen, R. Torronen, Food Res. Int., 99, 32, 345-353. 17. W. Mullen, J. McGinn, M. E. J. Lean, M. R. MacLean, P. Gardner, G. G. Duthie, T. Yokota, A. Crozier, J. Agric. Food Chem, 2002, 50, 5191-5196. http://dx.doi.org/10.1021/jf020140n 18. V. T. Tumbas, J. M. Canadanovic-Brunet, D. D. Cetojevic-Simin, G. S. Cetkovic, S. M. Dilas, L. Gille, J. Sci. Food Agric, 2012, 92, 1273-1281. http://dx.doi.org/10.1002/jsfa.4695 19. H. H. Lin, H. P. Huang, C. C. Huang, J. H. Chen, C. J. Wang, Mol. Carcinogen., 2005, 43, 86-89. http://dx.doi.org/10.1002/mc.20103 20. J. Piljac-Zegarac, L. Valek, S. Martinez, A. Belscak, Food Chem. 2009, 113, 394-400. http://dx.doi.org/10.1016/j.foodchem.2008.07.048 21. R. Margerita, E. Giussania, R. Morelli, R. L. Scalzoc, R. C. Nani, D. Torreggiani, Food Res. Int. 2003, 36, 999-1005. http://dx.doi.org/10.1016Zj.foodres.2003.07.002 22. 22. D. Torreggiani, E. Forni, I. Guercilena, A. Maestrelli, G. Bertolo, G. P. Archer, C. J. Kennedy, S. Bone, G. Blond, E. Contreras-Lopez, D. Champion, Food Res. Int. 1999, 32, 441-446. http://dx.doi.org/10.1016/S0963-9969(99)00106-4 23. S. Oancea, C. Grosu, O. Ketney, M. Stoia, Acta Chim. Slov. 2013, 60,383-389. 24. Y. Y. Lim, T. T. Lim, J. J. Tee, Food Chem. 2007, 103, 10031008. http://dx.doi.org/10.1016/j.foodchem.2006.08.038 25. P. Deetae, P. Parichanon, P. Trakunleewatthana, C. Chansee-tis, S. Lertsiri, Food Chem. 2012, 133, 953-959. http://dx.doi.org/10.1016/j.foodchem.2012.02.012 Povzetek Sadje spada med glavne prehranske vire bioaktivnih spojin. Zaradi pozitivnih učinkov na zdravje, je na trgu prisotnih veliko funkcionalnih živil narejenih iz sadja in tudi sadnih čajev, veča pa se tudi zanimanje za raziskave njihove hranilne vrednosti in kakovosti. Cilji naše raziskave so bili: 1) določitev vsebnosti skupnih fenolnih spojin (TPC), vsebnosti skupnih antocianinov (TAC), antioksidativne aktivnosti (AA), koncentracije učinkovitosti (IC50), prooksidativneak-tivnosti (Pro-ox) in »Pro-Antidex« 12 komercialno dostopnih sadnih čajev; 2) klasifikacija analiziranih čajev; 3) ocena podobnosti vzorcev. TPC je bila med 12,5 in 29,3 mg ekvivalentov galne kisline (GAE) / g čaja, TAC med 2,6 in 5,6 mg cianidin-3-glukozida (Cy-3-glu) / g čaja, AA pa v območju od 10,9 do 19,1 mgaskorbinske kisline (AAE) / g čaja. Pro-ox je bila v območju od 3,9 do 10,0 mg / mL ekstrakta čaja, Pro-Antidex pa od 3,3 do 7,3. Moldovan et al.: Total Phenolics, Total Anthocyanins, Antioxidant ... 220 Acta Chim. Slov. 2016, 63, 220-226 DOI: 10.17344/acsi.2015.1541 Scientific paper Rapid Electrochemical Method for the Determination of L-DOPA in Extract From the Seeds of Mucuna Prurita Dalibor M. Stankovi},1* Anchalee Samphao,2 Biljana Dojcinovi}3 and Kurt Kalcher4 1 Innovation center of the Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, Serbia 2 Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani, 34190, Thailand 3 Institute for Chemistry, Technology and Metallurgy, University of Belgrade 11000 Belgrade, Serbia 4 Institute of Chemistry - Analytical Chemistry, Karl-Franzens University Graz, A-8010 Graz, Austria * Corresponding author: E-mail: dalibors@chem.bg.ac.rs Phone: 00381 11 3336829 Received: 18-03-2015 Abstract This work presents the electrochemical behavior of levodopa (L-DOPA), at boron-doped diamond (BDD) electrodes, using cycling voltammetry (CV), in Britton-Robinson (BR) buffer solution, and application of the proposed electrode for the determination of L-DOPA in extracts from the seeds of velvet bean (Mucuna prurita Hook or Mucuna pruriens (L.) DC.). L-DOPA provides a well-defined and single oval-shape oxidation peak at +0.8 V vs. Ag/AgCl (3 M KCl) reference electrode in BR buffer solution at pH 3.0. Experimental parameters, such as pH of supporting electrolyte and square wave voltammetry (SWV) operating parameters (frequency and modulation amplitude) were optimized. The effect of possible interferences was evaluated. Under optimal conditions the detection limit of the developed method was 0.8 |M and the calibration curve for L-DOPA was linear in the range from 2 to 100 |M. The proposed method was successfully applied to the determination of L-DOPA in an extract from the seeds of Mucuna prurita. The obtained result was in good agreement with obtained by photometry with 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS). The developed approach can be beneficial for the quantification of L-DOPA using a BDD electrode as up-to-date potential alternative sensor for electroanalytical applications. Keywords: L-DOPA, boron-doped diamond electrode, square wave voltammetry 1. Introduction Mucuna prurita is a medicinal plant which is mentioned in the Indian system of medicines including folk medicines mostly due its management of diabetes, which is effective either individually or in combinations with other plants.1 The seeds of this plant, which also possess anti-inflammatory effect, have been used as a tonic and aphrodisiac for male virility.2 Anti-Parkinsonism effects have been reported for the seed, and this can be attributed to the L-DOPA presence. Levodopa shows high importance in the brain neurotransmission processes. The precursor of dopamine can cross the blood brain barrier and at the action site be converted to dopamine.3 According to these statements reliable, a cost-effective, and sensitive analytical procedure for its quantification can play an important role in this field. L-DOPA (levodopa, 3,4-dihydroxy-l-phenylalanine) is widely used as a source of dopamine in the treatment of most patients with Parkinson's disease and epilepsy.4 This drug can be principally metabolized by an enzymatic reaction (dopa decarboxylase) to dopamine compensating for the deficiency of dopamine in the brain.5 Together with the positive effect, several side effects are attributed to the long term use of this drug, such as paranoia and Stankovic et al.: Rapid Electrochemical Method for the Determination Acta Chim. Slov. 2016, 63, 220-226 221 dyskinesia.6-7 Based on these facts, different analytical methods, usually based on chromatographic techniques and spectrophotometry, are employed for the quantification of this compound.8-17 They possess satisfactory sensitivity and selectivity but the disadvantage of these methods lies in expensive instrumentation and time consuming sample preparation. Also, electroanalytical methods have been presented for the quantification of levodopa.18-21 Some of the described methods require long time electrode preparation and limited life time which can strongly influence the reproducibility of these electrodes. Usage of novel solid electrode materials can be beneficial in the field of electroanalysis. Boron doped diamond electrodes, nowadays, belong to the group of one of the best solid electrode materials. This electrode is widely investigated and has been found as powerful tool for the quantification of biologically active compounds.22, 23 Based on all these facts, the aim of this work was to develop a novel, simple, rapid and sensitive electrochemical method for the determination of L-DOPA in extracts from the seeds of Mucuna prurita with a boron-doped diamond electrode as electrochemical sensor. The voltamme-tric behavior of L-DOPA was investigated. After optimization of the experimental procedure and investigation of the influence of some interferents the method was successfully applied to the determination of L-DOPA in the real sample. 2. Experimental 2. 1. Chemicals and Solutions 3,4-Dihydroxy-L-phenylalanine (L-DOPA), ascorbic acid (AA), dopamine (DOP), uric acid (UA), boric acid, sodium hydroxide, ethanol, acetic acid and phosphoric acid were of analytical grade, purchased from Sigma Aldrich, USA. Britton-Robinson buffer solution was used as supporting electrolyte and it was prepared by mixing aqueous solutions (0.04 M) of boric, phosphoric and acetic acid. The pH values were adjusted with sodium hydroxide (0.2 M). All solutions were prepared using Millipore water. Stock solution of the L-DOPA (10-3 M) was prepared in 50% aqueous ethanol. Calibration standard solutions were prepared from the stock solution by appropriate dilution with supporting electrolyte. 2. 2. Apparatus Cyclic voltammetric (CV) and square-wave voltam-metric (SWV) measurements were performed using an electrochemical system AUTOLAB PGSTAT 302N, Methrom Autolab B.V. (The Netherlands) controlled by the corresponding software (NOVA 1.10). The cell (10 mL) consisted of a three-electrode system, the boron-doped diamond electrode (inner diameter: 3 mm; Windsor Scientific Ltd., Slough, Berkshire, United Kingdom), an Ag/AgCl (saturated KCl) reference electrode and a Pt counter electrode. All potentials reported in this paper are given vs. the Ag/AgCl (3 M KCl) reference electrode at an ambient temperature. All pH values were measured with a pH meter model Orion 1230, equipped with a WTW combined electrode. The potential was swept over the range from 0 to +1.2 V (vs. Ag/AgCl) at different scan rates for CV, and from 0.3 to + 1.2 V at the optimized instrumental parameters (step potential 5 mV, frequency 30 Hz, and modulation amplitude 60 mV) for square-wave voltammetry. 2. 3. ABTS Method ABTS^+ radical solution was prepared by mixing equal volumes of the ABTS stock solution (7 mM in water) with 2.45 mM of potassium persulfate. This mixture was allowed to stand for 12-16 h at room temperature in the dark. For ABTS determinations different concentrations of L-DOPA solutions were prepared in the same range as for SWV (2 - 100 pM). The standard solutions of L-DOPA were mixed with the ABTS^+ radical solution (to made ABTSV concentration about 65 pM), and the absor-bance was measured at 734 nm. The absorbance of ABTSV was adjusted to 0.7 by dissolving with ethanol (blank), and 10 pM of standard L-DOPA solution was added in 1 mL of ABTS^+. Five min was allowed to produce inhibition of the blank absorbance. The same procedure was applied for sample analysis and the results were calculated from the calibration curve. 2. 4. Sample Preparation Dried seeds of Mucuna prurita were purchased from the store Magic Garden Seeds, Regensburg, Germany, in the year 2012. The extraction procedure was done according to previously described literature data.24 The powdered plant material (3.2270 g) was soaked with 0.1 M HC-l (10 mL) for 1 hour. The prepared mixture was placed in a water bath (80 °C) for 5 min, and cooled to room temperature. After the addition of ethanol (10 mL) and shaking (10 minutes), the mixture was centrifuged (10 min, 4000 rpm, Rotine 420R, Hittech, Germany). The supernatant was collected and the extraction with ethanol was repeated. Finally, the combined supernatants were diluted with ethanol to a volume of 50 mL and were stored in the fridge at 4 °C. 3. Results and Discussions 3. 1. Effect of pH and Scan Rate on the Voltammetric Behavior of L-DOPA at a Boron-doped Diamond Electrode The effect of pH on the peak current (CV) for the oxidation of L-DOPA was evaluated with BR buffer solu- Stankovic et al.: Rapid Electrochemical Method for the Determination 222 Acta Chim. Slov. 2016, 63, 220-226 a) Figure 1. a) Cyclic voltammograms of L-DOPA in BR buffer solution (pH 3.0) at a boron doped diamond electrode; dotted line - blank; L-DOPA concentration 0.1 mM. b) Dependence of peak current (full dots) and peak potential from the pH of the supporting electrolyte. tion as a supporting electrolyte. L-DOPA (0.1 mM) provides a well-defined peak in acidic medium at a potential of around + 0.8 V (Fig. 1. A). The highest oxidation peak current was obtained in a supporting electrolyte solution at pH 3 (Fig. 1. B). With increasing pH the obtained signal becomes broader with a concomitant decrease of the peak current. For all further experiments pH 3.0 was chosen as supporting electrolyte. On the reverse scan the analyte provides a reduction peak at a potential around 0.0 V. With a potential difference between the anodic and cathodic peaks of around 0.8 V, the electrochemical redox behavior of L-DOPA at BDD electrode can be considered as a quasi-reversible process. In order to investigate the nature of the electrochemical reaction of L-DOPA at a BDD electrode, the effect of the scan rate was evaluated in BR buffer solution at pH 3.0. From Fig. 2 A and B it is obvious that an increase of the scan rate is followed with a linear increase of both peak currents. The current is linearly dependent on the square root of the scan rate. The corresponding equations obtained from these measurements are Ia(pA) = 0.2469 x v1/2(V s-1)1/2 + 0.0531, (R2 = 0.9961) and Ic (M) = -0.1570 x v1/2(V s-1)1/2+ 0.1331, (R2 = 0.9992), where Ia presents the oxidation peak current and Ic the corresponding reduction peak current. Both currents are linearly dependent on the square root of the scan rate, which suggests that both processes, oxidation and reduction are diffusion controlled. Small shifts in the peak potentials when varying the scan rate confirm that the electrochemical reactions are quasi-reversible. 3. 2. Optimization of Square Wave Voltammetric Parameters Electrochemical methods due to their characteristics, offer rapid, low-cost, sensitive and selective procedures for Figure 2. a) Cyclic voltammograms of L-DOPA (0.1 mM) at a BDDE ; supporting electrolyte BR buffer solution pH 3.0; scan rates 10, 20, 30, 50, 75, 100, 150 and 200 mV/s. b) Dependences of the oxidation and reduction peak currents from the square root of the scan rate. Stankovic et al.: Rapid Electrochemical Method for the Determination Acta Chim. Slov. 2016, 63, 220-226_ 223 the quantification of numerous biologically active compounds. Square wave voltammetry with optimized instrumental parameters can become a suitable method for the determination of these compounds, due to its low background current and low detection limit. According to this, the most important SWV instrumental parameters, such as modulation amplitude and frequency were investigated (data not shown). All experiments were done with 0.1 mM L-DOPA in Britton-Robinson buffer solution at pH 3.0. The influence of the modulation amplitude on the oxidation peak current of L-DOPA was studied in the range from 10 to 100 mV. Other parameters were at fixed value, i.e., the frequency was 10 Hz and the step potential 5 mV. With increase of the modulation amplitude, the peak current increased rapidly to a value of 60 mV. Further increase of the modulation amplitude produced a wider peak shape and a decrease of the current. Thus, a value of 60 mV was selected as optimum for the determination of L-DOPA, and was used for all further experiments. When varying the frequency from 10 to 100 Hz with modulation amplitude of 60 mV, the peak current increased up to a value of 30 Hz. At higher frequency the peak current leveled off to a constant value and finally even decreased. The most suitable peak was observed at a frequency of 30 Hz. Taking into account peak current and peak resolution the optimized experimental conditions (amplitude of 60 mV and frequency of 30 Hz) were used for all further experiments. 3. 3. Calibration Curve Calibration curves were constructed by plotting the oxidation peak current against the concentration of the analyte. The dependence was linear in the range from 2 to 100 pM (Fig. 3 A and B). The corresponding regression equation obtained from these measurements can be expressed as ¡a(yA) = 0.0294 c (pM) + 0.0068 (R2 = 0.9989), with a detection limit 0.8 pM. Under optimized experimental conditions the repeatability from 6 measurements (c = 10 pM) was 2.3 %. This value indicates that the proposed method has excellent repeatability. Characteristics of the developed methodology are comparable or better than those proposed in the literature. 12 The advantages of the developed method lie in the use of a solid electrode without any modification, wide dynamic range and possible application in complexes matrices such as extracts from plants containing L-DOPA. 3. 4. Effect of Possible Interferences Ascorbic acid (AA), uric acid (UA) and dopamine (DOP) are frequently accompanying L-DOPA in drugs and/or in urine samples; their effect as possible interferents on the peak current obtained for L-DOPA (c = 0.1 mM) was examined. For this purpose the mixed solution method was used with a concentration of all three tested interfering compounds of 0.1 mM. From Fig. 4 it can be concluded that L-DOPA shows an oxidation peak potential similar to the interferences, which results in an increase of the current. In the presence of ascorbic acid and uric acid (cAA = cUA) the peak current for L-DOPA increased for 10-15 %. In the case of dopamine (cDOP = 0.1 mM) the peak current obtained for L-DOPA increased for 45 %. The resulting voltammograms of L-DOPA are presented in Fig. 4 B-D. 3. 5. Analytical Application The proposed method was applied for the determination of L-DOPA in extracts from the seeds of Mucuna a) b) c(MM) Figure 3. a) SW voltammograms of L-DOPA at a BDDE obtained for different concentrations (2 to 100 ||M) under optimized experimental conditions. b) Calibration curve obtained from these measurements. Stankovic et al.: Rapid Electrochemical Method for the Determination 224 Acta Chim. Slov. 2016, 63, 220-226 224 Figure 4. a) Relative peak currents of L-DOPA (0.1 mM) in the absence (left bars) and in the presence (right bars) of interferents (0.1 mM) under optimized experimental conditions. B-d) presents voltammograms from these measurements, for uric acid (UA), ascorbic acid (AA) and dopamine (DOP), respectively. 250 jiL /200 A \ / / 100 fiL^^X^7 ?- 0.4 0.6 0.8 1.0 1.2 E(V) Figure 5. SW voltammograms of a velvet bean extract recorded with a BDDE for different sample volumes (100, 200 and 250 |L in 10 mL of total volume) by the proposed electroanalytical method under optimized conditions. prurita. Three different volumes of sample of 100, 200 and 250 |L were diluted with supporting electrolyte to make final volume of the 10 mL and signals were recorded with SWV at BDD electrode, under optimized experimental conditions. Representative voltammograms are presented in Fig. 5. All measurements were repeated three times and concentrations of L-DOPA were calculated from the calibration curve. ABTS method was used as a Table 1. Determination of the L-DOPA content in extract from the seeds of Mucuna prurita Proposed Reference Literature Sample method method data24 L-DOPA (%) L-DOPA (%) L-DOPA (%) Extract from seeds of 5.1 ± 0.1 5.1 ± 0.1 3.1-6.1 Mucuna prurita Stankovic et al.: Rapid Electrochemical Method for the Determination Acta Chim. Slov. 2016, 63, 220-226 225 reference method for comparison of the results obtained for the contents of L-DOPA in the extract. According to the data presented in Table 1, it can be concluded that the result obtained with the proposed method is in good agreement with the value obtained by the spectrophotometry method and corresponds to the literature data.24 4. Conclusions Using a boron-doped diamond electrode in combination with square wave voltammetry we developed a fast, low-cost, simple and sensitive method for the determination of L-DOPA in extracts from the seeds of velvet beans (Mucuna prurita). A detection limit of 0.8 pM and a dynamic working concentration range from 2 to 100 pM were obtained. It was found that dopamine strongly interfers with L-DOPA quantification and that the presence of ascorbic and uric acid, at the same concentration level as the analyte, cause an increase of the oxidation peak increase of 10-15%. The method was successfully applied to the determination of L-DOPA in a real sample. The results indicated that the developed methodology can be beneficial for the field of electroanalytical chemistry. 5. Acknowledgements This work has been supported by the Ministry of Education and Science of the Republic of Serbia (project No. OI 172030) and JoinEU-SEE-Penta Erasmus Mundus scholarship. A.S. acknowledges financial mobility support from Asea UniNet. 6. Reference 1. A. Kar, B. K. Choudhary, N. G. Bandyopadhyay, J. Ethnop-harmacol. 2003, 84, 105-108. http://dx.doi.org/10.1016/S0378-8741(02)00144-7 2. Anonymous, The Wealth of India, PID, CSIR, New Delhi, 1962, pp. 439-444. 3. P. Kulhalli, Parkinson's disease therapy - an overview. Heritage Heal. July 1999. 29-30. 4. E. R. Ritvo, A. Yuwiler, E. Geller, A. Kales, S. Rashkis, A. Schicor, S. Plotkin, R. http://dx.doi.org/10.1007/BF01537957 Axelrod, C. Howard, J. Autism Dev. Disord. 1971, 1, 190-205. 5. K. D. Barron. Pathology. In: Factor SA, Weiner WJ, editors. Parkinson's disease: Diagnosis and clinical management. New York: Demos Medical Publishing; 2002. Chapter 20. 6. A. Barbeau, Adv. Neurol. 1974, J, 347-365. 7. L. V. Laitinen, A. T. Bergenheim, M. I. Hariz, J. Neurosurg. 1992, 76, 53-61. http://dx.doi.Org/10.3171/jns.1992.76.1.0053 8. G. Cannazza, A. Di Stefano, B. Mosciatti, D. Braghiroli, M. Baraldi, F. Pinnen, P. Sozio, C. Benatti, C. Parenti, J. Pharm. Biomed. Anal. 2005, 36, 1079-1084. http://dx.doi.org/10.1016/jjpba.2004.09.029 9. A. Tolokan, I. Klebovich, K. Balogh-Nemes, G. Horvai, J. Chromatogr. B 1997, 698, 201-207. http://dx.doi.org/10.1016/S0378-4347(97)00288-0 10. M. I. H. Helaleh, N. Rahman, E. S. M. Abu-Nameh, Anal. Sci. 1997, 13, 1007-1010. http://dx.doi.org/10.2116/analsci.13.1007 11. P. Nagaraja, K. C. S. Murthy, K. S. Rangappa, N. M. M. Gowda, Talanta 1998, 46, 39-44. http://dx.doi.org/10.1016/S0039-9140(97)00245-2 12. M. F. S. Teixeira, L. H. Marcolino-J'unior, O. Fatibello-Fil-ho, E. R. Dockal, M. F. Bergamini, Sens. Actuator. B Chem. 2007, 122, 549-555. 13. C. Hansson, G. Agrup, H. Rorsman, A. M. Rosengren, J. Chromatogr. 1979, 162, 7-22. 14. S. Zhao, W. Bai, B. Wang, M. He, Talanta 2007, 73, 142146. http://dx.doi.org/10.1016Zj.talanta.2007.03.023 15. L. Zhang, G. Chen, Q. Hu, Y. Fang, Anal. Chim. Acta 2001, 431, 287-292. http://dx.doi.org/10.1016/S0003-2670(00)01327-1 16. W. W. He, X. W. Zhoua, J. Q. Lua, J. Chromatogr. A 2006, 1131, 289-292. http://dx.doi.org/10.1016/j.chroma.2006.08.071 17. K. Reddaiah, T. Madhusudana Reddy, P. Raghu, J. Electroa-nal. Chem. 2012, 682, 164-171. http://dx.doi.org/10.1016/jjelechem.2012.07.027 18. X. X. Yan, D. W. Pang, Z. X. Lu, J. Q. Lu, H. Tong, J. Elec-troanal. Chem. 2004, 569, 47-52. http://dx.doi.org/10.1016/jjelechem.2004.02.011 19. X. Yan, D. Pan, H. Wang, X. Bo, L. Guo, J. Electroanal. Chem. 2011, 663, 36-42. http://dx.doi.org/10.1016/jjelechem.2011.09.024 20. A. Babaei, M. Sohrabi, A. R. Taheri, J. Electroanal. Chem. 2013, 698, 45-51. http://dx.doi.org/10.1016/jjelechem.2013.01.021 21. S. Shahrokhian, E. Asadian, J. Electroanal. Chem. 2009, 636, 40-46. http://dx.doi.org/10.1016/jjelechem.2009.09.010 22. K. Peckova, J. Musilova, J. Barek, Crit. Rev. Anal. Chem. 2009, 39, 148-172. http://dx.doi.org/10.1080/10408340903011812 23. K. Peckova, J. Barek, Curr. Org. Chem. 2011, 15, 30143028. http://dx.doi.org/10.2174/138527211798357164 24. P. Siddhuraju, K. Vijayakumari, K. Janardhanan, J. Agric. Food Chem. 1996, 44, 2636-2641. http://dx.doi.org/10.1021/jf950776x Stankovic et al.: Rapid Electrochemical Method for the Determination 226 Acta Chim. Slov. 2016, 63, 220-226 226 Povzetek Z uporabo ciklične voltametrije smo študirali elektrokemijsko obnašanje levodope (L-DOPA) na z borom dopirani diamantni elektrodi v Britton-Robinsonovem (BR) pufru. Proučili smo tudi možnost uporabe omenjene elektrode za določanje L-DOPA v ekstraktih iz semen rastlin Mucuna prurita Hook ali Mucuna pruriens (L.) DC. Optimizirali smo eksperimentalne parametre kot so pH nosilnega elektrolita in parametri (frekvenca in modulacija amplitude) voltametrije s kvadratnim spreminjanjem potenciala (SWV). Proučevali smo tudi vpliv možnih interferenc. Pri optimalnih pogojih je meja zaznave razvite metode 0,8 |M, umeritvena krivulja za L-DOPA pa linearna v območju od 2 do 100 |M. Metodo smo uspešno uporabili za določanje L-DOPA v izvlečkih pripravljenih iz semen Mucuna prurita. Stankovic et al.: Rapid Electrochemical Method for the Determination DOI: 10.17344/acsi.2015.1668 Acta Chim. Slov. 2016, 63, 227-240 227 Scientific paper New Approaches for the Synthesis, Cytotoxicity and Toxicity of Heterocyclic Compounds Derived from 2-Cyanomethylbenzo[c]imidazole Rafat M. Mohareb,1* Abeer A. Mohamed2 and Amira E. M. Abdallah3 1 Department of Chemistry, Faculty of Science, Cairo University, Giza, A. R. Egypt 2 National Organization for Research & Control of Biologicals, Giza, Egypt 3 Department of Chemistry, Faculty of Science, Helwan University, Cario, Egypt * Corresponding author: E-mail: raafat_mohareb@yahoo.com Received: 04-05-2015 Abstract The reaction of ethyl cyanoacetate with o-phenylenediamine gave the 2-cyanomethylbenzo[c]imidazole (1). The latter compound was used as the key starting material to synthesise biologically active heterocyclic derivatives. Thus, the reaction of 1 with cyclohexanone and either of benzaldehyde, 4-methoxybenzaldehyde or 4-chlorobenzaldehyde gave the annulated derivatives 2a-c, respectively. The antitumor evaluations of the newly synthesized products against the three cancer cell lines MCF-7 (breast adeno-carcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer) showed that compounds 2b, 6, 11b, 11c, 12b, 16a, 16b and 18a exhibited optimal cytotoxic effect against cancer cell lines, with IC50 values in the nM range. Bioactive compounds are often toxic to shrimp larvae. Thus, in order to monitor these chemicals in vivo lethality to shrimp larvae (Artemia salina), Brine-Shrimp Lethality Assay was used. Compounds 11b, 12b and 16b showed no toxicity against the tested organisms. Keywords: benzimidazole, thiophene, thiazole, synthesis, anti-tumor, toxicity 1. Introduction In recent years benzimidazole derivatives have provided a large number of biologically active compounds that have been intensively used in medicinal chemistry as drugs. They are structural isosteres of naturally occurring nucleotides, which allow them to interact easily with the biopolymers of the living systems and various kinds of biological activities have been obtained. Some 2-aminobenzimidazoles display an appreciable antimicrobial effect. Their corresponding carbamate derivatives have been synthesized for their significant in vivo antifilarial activity.1 Concerning the high affinity that they display towards a variety of enzymes and protein receptors, they could be considered as pivotal structures in drug design.2 Optimization of benzimidazole-based structures has resulted in marketed drugs, e.g. Omeprazole3 and Pimobendan4 that are therapeutically useful in the management of peptic ulcer and congestive heart failure, respectively. Many derivatives of benzimidazoles are well known for their antimicrobial,5-10 anthelmintic,11 antiviral,12-16 and antifungal17,18 activities. Since 1985 benzimidazole containing compounds have been reported as well known anticancer agents.19-25 The role of mammalian DNA topoisomerases as molecular targets for anticancer drugs has been recognized. Some benzimidazoles have been reported as topoisomerase inhibitors, e.g. Hoechst 33258 and Hoechst 33342 (Fig. 1).26,27 As the extension of this work, head to head bis-benzimidazole compounds proved high efficacy as DNA binders.28 Some widely used anticancer drugs such as RAF265 (CHIR-265; Novartis Pharmaceuticals, Basel, Switzerland) and AZD6244 (ARRY-142886; AstraZene-ca, London, England) are known to contain benzimida-zole moiety. RAF265 resulted in a reduction in tumor cell growth and in tumor cell apoptosis.29 Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity 228 Acta Chim. Slov. 2016, 63, 227-240 Hoechst 33342 Fig. 1. Examples of topoisomerase inhibitors containing benzimidazole nucleus. 2. Results and Discussion 2. 1. Chemistry The 2-cyanomethylbenzo[c]imidazole (1) obtained from the reaction of ethyl cyanoacetate with o-phenylene- diamine was used as the key starting material to synthe-sise biologically active heterocyclic derivatives. Thus, the reaction of 1 with cyclohexanone and any of benzaldehyde, 4-methoxybenzaldehyde or 4-chlorobenzaldehyde gave the annulated derivatives 2a-c, respectively. The analy- Scheme 1. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity 229 Acta Chim. Slov. 2016, 63, 227-240 tical and spectral data of 2a-c were consistent with their respective structures. Thus, the NMR spectrum of 2a (as an example) showed 2.49-2.88 (CH2-cyclohexanone), 7.13-8.01 (m, 9H, C6H4 C6H5). Moreover, the 13C NMR data revealed 38.6, 39.0, 40.2, 40.6 (4 x CH2-cyclohexa-none), 116.2 (CN), 120.3, 122.8, 124.9, 127.8, 128.0, 129.8, 131.2, 132.6, 134.5, 134.8, 144.3, 146.8, 150.4 (2 x C6H4, pyridine C), 164.8 (C=N). The reaction of 1 with acetoacetanilide gave the ben-zo[c]pyrazolo[3,2-a]pyridine derivative 3. The latter compound reacted with benzene diazonium chloride to give the phenylazo derivative 4 (Scheme 1). On the other hand, the reaction of 1 with acetic acid/acetic anhydride mixture gave the N-acetyl derivative 5. Compound 5 readily underwent bromination when treated with bromine in acetic acid solution at 60 oC to give the N-a-bromoacetylbenzo[c]imi-dazole derivative 6. The latter compound as a-bromocar-bonyl compound showed interesting chemical reactivity when treated with some chemical reagents. Thus, the reaction of 6 with potassium cyanide gave the benzo[c]imida-zo[2,3-fc]pyridine derivative 7. On the other hand, the reaction of 6 with hydrazine hydrate afforded the hydrazine de- Scheme 1. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity 230 Acta Chim. Slov. 2016, 63, 227-240 rivative 8. Compound 6 reacted with thiourea in ethanol to give the thiazole derivative 9 (Scheme 2). Recently, our research group was involved in a comprehensive program involving the reaction of active methylene reagents with phenylisothiocyanate in basic (KOH) dimethylformamide to form the intermediate potassium sulphide salt. The latter undergoes heterocycliza-tion when reacted with a-halocarbonyl compounds to give either thiophene or thiazole derivatives depending on the nature of the a-halocarbonyl compound and the reaction conditions.30-32 Thus, the reaction of 5 with phenylisothiocyanate in DMF/KOH solution gave the intermediate potassium sulphide salt 10. The latter intermediate underwent heterocyclization when reacted with any of a-chloroacetone, ethyl chloroacetate or a-bromoacetophe-none to give the thiophene derivatives 11a-c, respectively. The analytical and spectral data of 11a-c are consistent with their respective structures. Scheme 3. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity 231 Acta Chim. Slov. 2016, 63, 227-240 The reaction of 5 with either benzaldehyde or sa-licylaldehyde gave the benzylidene derivatives 12a and 12b, respectively. On the other hand, the reaction of 5 with either malononitrile or ethyl cyanoacetate in DMF containing triethylamine gave the 1,5-dihydroben-zo[4,5]imidazo[1,2-a]pyridine derivatives 13a and 13b, respectively (Scheme 3). Compound 5 reacted with acetophenone in an oil bath at 120 °C to give the Knoevenagel condensation pro- duct 14. The latter compound reacted with benzaldehyde to give the benzylidene derivative 15. The reactivity of 5 towards the well-known Gewald's thiophene synthesis was studied to give biologically active thiophene derivatives. Thus, the reaction of 5 with elemental sulfur and either of malononitrile or ethyl cyanoacetate gave the thiophene derivatives 16a and 16b, respectively. On the other hand, the reaction of 5 with benzenediazo-nium chloride in ethanol/sodium hydroxide solution affor- Scheme 1. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity 232 Acta Chim. Slov. 2016, 63, 227-240 ded the phenylhydrazo derivative 17. Compound 17 underwent the Gewald's thiophene synthesis through the N-acetyl moiety when reacted with elemental sulfur and either of malononitrile or ethyl cyanoacetate in 1,4-dioxane containing triethylamine under reflux to give the thiophene derivatives 18a and 18b, respectively (Scheme 4). 3. Anti-tumor and Normal Cell Line Activity Tests 3. 1. Chemicals Reagents: Fetal bovine serum (FBS) and L-glutami-ne were from Gibco Invitrogen Co. (Scotland, UK). RP-MI-1640 medium was from Cambrex (New Jersey, USA). Dimethyl sulfoxide (DMSO), doxorubicin, penicillin, streptomycin and sulforhodamine B (SRB) were from Sigma Chemical Co. (Saint Louis, USA). 3. 1. 1. Cell Cultures Three human tumor cell lines, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), and SF-268 (CNS cancer) were used. MCF-7 was obtained from the European Collection of Cell Cultures (ECACC, Salisbury, UK), NCI-H460, SF-268 and normal fibroblast were grown as monolayer and routinely maintained in RPMI-1640 medium supplemented with 5% heat inactivated FBS, 2 mM glutamine and antibiotics (penicillin 100 U/mL, streptomycin 100 ^g/mL), at 37 oC in a humidified atmosphere containing 5% CO2. Exponentially growing cells were obtained by plating 1.5 x 105 cells/mL for MCF-7 and SF-268 and 0.75 x 104 cells/mL for NCI-H460, followed by 24 h of incubation. The effect of the vehicle solvent (DMSO) on the growth of these cell lines was evaluated in all the experiments by exposing untreated control cells to the maximum concentration (0.5%) of DMSO used in each assay. 3. 1. 2. TUmor Cell Growth Assay The effects of 2a-c to 18a,b on the in vitro growth of human tumor cell lines were evaluated according to the procedure adopted by the National Cancer Institute (NCI, USA) in the zIn vitro Anticancer Drug Discovery Screen' that uses the protein-binding dye sulforhodamine B to assess cell growth.33 Briefly, exponentially, cells growing in Table 1. Effect of newly synthesized compounds on the growth of three human tumor cell lines C d GISo mol L1) Compound MCF-7 NCI-H460 SF-268 WI 38 2a 33.0 ± 1.4 20.8 ± 4.3 20.3 ± 2.8 38.4 ± 2.90 2b 0.8 ± 0.04 0.5 ± 0.02 0.06 ± 0.001 20.0 ± 4.94 2c 22.1 ± 10.4 30.8 ± 10.8 26.1 ± 2.8 28.2 ± 0.8 3 33.6 ± 10.2 40.0 ± 8.6 38.6 ± 8.0 8 >100 4 32.2 ± 3.6 36.3 ± 12.5 40.6 ± 8.8 50.7 ± 8.2 5 22.8 ± 8.30 22.8 ± 4.32 22.8 ± 6.23 44.8 ± 6.0 6 0.01 ± 0.001 0.02 ± 0.004 0.06 ± 0.002 >100 7 28.4 ± 5.8 22.7 ± 8.2 30.4 ± 2.4 18.6 ±4.0 8 23.55 ± 4.06 34.6 ± 12.06 45.41 ± 2.16 >100 9 33.6 ± 8.5 40.3 ± 12.3 30.4 ± 2.8 62.2 ± 2.0 11a 26.4 ± 2.10 12.42 ± 3.01 10.63 ± 2.83 >100 11b 0.81 ± 0.04 0.52 ± 0.04 0.08 ± 0.006 40.0 ± 1.3 11c 1.6 ± 0.4 0.6 ± 0.16 1.8 ± 0.06 22.4 ±1.6 12a 26.2 ± 2.4 28.6 ± 2.8 26.8 ± 8.5 30.2 ± 2.6 12b 0.02 ± 0.001 0.03 ± 0.006 0.06 ± 0.008 > 100 13a 30.22 ± 6.12 28.99 ± 4.70 10.39 ± 6.80 > 100 13b 12.6 ± 2.01 18.6 ± 6.06 30.4 ± 2.36 30.6 ± 10.2 14 12.33 ± 2.16 16.36 ± 2.26 18.20 ± 5.28 55.5 ±8.3 15 30.7 ± 6.2 38.5 ± 6.4 37.5 ± 8.0 66.0 ± 18.4 16a 2.6 ± 2.8 6.6 ± 2.2 5.0 ± 1.81 0.5 ± 5.1 16b 0.06 ± 0.006 0.06 ± 0.006 0.02 ± 0.008 >100 17 38 ± 4. 18 39.03 ± 8.01 22.59 ± 4.01 20.20 ± 8.2 18a 0.08 ± 0.002 0.08 ± 0.003 0.02 ± 0.002 >100 18b 36.0 ± 7.3 26.7 ± 2.8 30.4 ± 2.9 32.6 ± 6.4 Doxorubicin 0.04 ± 0.008 0.09 ± 0.008 0.09 ± 0.007 > 100 Results are given in concentrations that were able to cause 50% of cell growth inhibition (GI50) after a continuous exposure of 48 h and show means ± SEM of three-independent experiments performed in duplicate. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... Acta Chim. Slov. 2016, 63, 227-240 233 96-well plates were then exposed for 48 h to five serial concentrations of each compound, starting from a maximum concentration of 150 pM. Following this exposure period adherent cells were fixed, washed, and stained. The bound stain was solubilized and the absorbance was measured at 492 nm in a plate reader (Bio-Tek Instruments Inc., Power wave XS, Winooski, USA). For each test compound and cell line, a dose-response curve was obtained and the growth inhibition of 50% (GI50), corresponding to the concentration of the compounds that inhibited 50% of the net cell growth was calculated as described elsewhere. Doxorubicin was used as a positive control and tested in the same manner. derivatives 2a-c, it is clear that the cytotoxicity of 2b is higher than those of 2a and 2c. Such high cytotoxicity of 2b is attributed to the presence of the 4-chlorophenylisoquinoline moiety together with the benzimidazole moiety. The high cytotoxicity of 16b relative to 16a is also explained in terms of the presence of the 3-EtO moiety. On the other hand, by considering the (1H-benzo[d]imidazol-1-yl)-2-aminothiop-hene derivatives 18a and 18b it is clear that the presence of the 2-carbonitrile group present in 18a is responsible for its high potency. The bromo-1H-benzo[d]imidazole derivative 6 showed the maximum cytotoxicity effect towards the three cancer cell lines followed by acetyl-1H-benzo[d]imi-dazolhydroxyphenyl derivative 12b. 3. 1. 3. Structure Activity Relationship: From Table 1 it is clear that the benzimidazole moiety was found to be crucial for the cytotoxic effect of the cyclic compounds 2a-c to 18a,b. Compounds 2b, 6, 11b, 11c, 12b, 16a, 16b and 18a exhibited optimal cytotoxic effect against cancer cell lines, with IC50 values in the nM range. Comparing the cytotoxicity of the benzimidazothiophenes 11b and 11c, it is obvious that the cytotoxicity of 11b is higher than that of 11c. The presence of the 2-EtO group in 11b is responsible for its high potency. Considering the 7,8,9,10-tetrahydrobenzo[4,5]imidazo[1,2-fc]isoquinoline 3. 2. Toxicity Bioactive compounds are often toxic to shrimp larvae. Thus, in order to monitor these chemicals, in vivo lethality to shrimp larvae (Artemia salina), Brine-Shrimp Lethality Assay34 was used. Results were analyzed with LC50 program to determine LC50 values and 95% confidence in-tervals.35 Results are given in Table 2 for the compounds which exhibited optimal cytotoxic effect against cancer cell lines, being the eight compounds 2b, 6, 11b, 11c, 12b, 16a, 16b and 18a. The shrimp lethality assay is considered as a useful tool for preliminary assessment of toxicity, and it has Table 2. Toxicity of the most potent compounds against the cancer cell lines Compound Conc. (^g/mL) Mortalitya Toxicity LC50 Upper 95% lim Lower 95% lim 2b 10 100 1000 6 8 10 Very toxic 12.05 6 10 100 1000 1 6 10 Very toxic 18.38 11b 10 100 1000 0 0 2 Non toxic 982.15 11c 10 100 1000 0 5 10 Harmful 420.28 112.23 90.55 12b 10 100 1000 0 1 4 Non toxic 880.42 16a 10 100 1000 2 8 10 Very toxic 14.88 16b 10 100 1000 0 0 5 Non toxic 999.33 18a 10 100 1000 0 6 8 Harmful 22.70 210.59 160.22 a Ten organisms (A. salina) tested for each concentration. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... 234 Acta Chim. Slov. 2016, 63, 227-240 been used for the detection of fungal toxins, plant extract toxicity, heavy metals, cyano bacteria toxins, pesticides, and cytotoxicity testing of dental materials,36 natural and synthetic organic compounds.34 It has also been shown that A. salina toxicity test results have a correlation with rodent and human acute oral toxicity data. Generally, a good correlation was obtained between A. salina toxicity test and the rodent data. Likewise, the predictive screening potential of the aquatic invertebrate tests for acute oral toxicity in man, including A. salina toxicity test, was slightly better than the rat test for test compounds.37 In order to prevent the toxicity results from possible false effects originated from solubility of compounds and DMSO's possible toxicity effect, compounds were prepared by dissolving in DMSO in the suggested DMSO volume ranges. It is clear from Table 2 that 11b, 12b, and 16b showed no toxicity against the tested organisms. On the other hand, 2b, 6 and 16a are very toxic, in addition, 11c and 18a are harmful. 3. 2. 1. Toxicity Method All toxicity tests were 96-h static renewal tests and water quality measurements (dissolved oxygen, pH, temperature, salinity) were taken in the control containers each day. Tests were run in a Revcos Environmental Chamber at 25 °C, 20% salinity, and a 16-h light : 8-h dark cycle. A media change was made every 24 h. Larvae used for all tests were one to two days old and exposed in 600-mL glass beakers containing 400 mL of media with 10 larvae/beaker and three replicates/concentration. Larvae were fed newly hatched Artemia after daily media change. The concentration of each compound was taken in terms 10, 100 and 1000 mg/mL. Adult shrimp toxicity tests were also run to complete the grass shrimp toxicity profile. Adult shrimp (acclimated for two weeks before testing) were exposed in 4-L wide-mouth glass jars containing 2 L of media and 10 shrimp/jar with two replicates/concentration and were run under conditions as described above for larvae.38 4. Experimental All melting points are uncorrected. IR spectra were recorded on KBr discs on a PyeUnicam SP-1000 spectrophotometer. 1H and 13C NMR spectra were measured on a Varian EM-390-200 MHz in DMSO as solvent using TMS as internal standard, and chemical shifts are expressed as 5. Analytical data were obtained from the Microa-nalytical Data Unit at Cairo University, Giza, Egypt. General procedure for the synthesis of the imidazo [1,2-£]isoqumolines 2a-c To a solution of 1 (1.57 g, 10 mmol) in ethanol (25 mL) containing triethylamine (0.5 mL), cyclohexanone (0.98 g, 10 mmol) and any of benzaldehyde (1.06 g, 10 mmol), 4-chlorobenzaldehyde (1.40 g, 10 mmol) or 4-methoxybenzaldehyde (1.36 g, 10 mmol) were added. The reaction mixture was heated under reflux for 3 h, then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give greenish brown crystals. 11-Phenyl-7,8,9,10-tetrahydrobenzo[4,5]imidazo[1,2-¿]isoquinoline-6-carbonitrile (2a). Yield 2.26 g (70%); m.p. 223-225 °C; Anal. Calcd. for C22H17N3 (323.39): C, 81.71; H, 5.30; N, 12.99%; found: C, 81.60; 4.85; N, 13.20%. IR (KBr) v/cm-1 3092-3030 (CH aromatic), 2887 (CH-alph.), 2222 (CN), 1523 (C=N), 1589, 1437 (C=C). 1H NMR (DMSO-d6) 5 2.49-2.88 (m, 8H, 4CH2-cyclohexanone), 7.13-8.01 (m6 , 9H, C6H4, C6H5). 13C NMR (DMSO-d6) 5 38.6, 39.0, 40.2, 40.6 (4xCH2), 116.2 (CN), 120.3, 122.8, 124.9, 127.8, 128.0, 129.8, 131.2, 132.6, 134.5, 134.8, 144.3, 146.8, 150.4 (2xC6H4, pyridine C), 164.8 (C=N). MS (m/z) 323 (M+, 23%). 11-(4-Chlorophenyl)-7,8,9,10-tetrahydrobenzo[4,5] imidazo[1,2-£]isoquinolme-6-carbomtrile (2b). Yield 2.32 g (65%); m.p. 267-269 °C; Anal. Calcd. for C22H16ClN3 (357.84): C, 73.84; H, 4.51; N, 11.74%; found: C, 73.61; H, 4.38; N, 11.94%. IR (KBr) v/cm-1 3091- 3027 (CH aromatic), 2900 (CH-alph.), 2222 (CN), 1584, 1488 (C=C), 1523 (C=N). 1H NMR (DMSO-d6) 5 2.49-2.51 (m, 8H, 4CH2-cyclohexanone), 7.26-8.01 6(m, 8H, 2C6H4). 13C NMR (DMSO-d6) 5 38.8, 39.12, 39.7, 39.9 (4xCH2), 115.9 (CN), 120.0, 122.9, 125.8, 126.2, 130.2, 131.1, 134.5, 136.1, 138.4, 140.2, 144.9, 145.6, 150.3 (2xC6H4, pyridine-C), 165.2 (C=N). MS (m/z) 357 (M+, 80%). 11-(4-Methoxyphenyl)-7,8,9,10-tetrahydrobenzo[4,5] imidazo[1,2-£] isoquinoline-6-carbonitrile (2c). Yield 2.58 g (73%); m.p. 243-246 °C; Anal. Calcd. for C23H19N3O (353.42): C, 78.16; H, 5.42; N, 11.89%; found: C, 777.33; H, 4.05; N, 11.06%. IR (KBr) v/cm-1 3103-3015 (CH aromatic), 2901-2838 (CH-alph.), 2212 (CN), 1643 (C=O), 1512 (C=N), 1589, 1446 (C=C). 1H NMR (DMSO-d6) 5 1.30 (s, 3H, CH3), 2.49-2.51 (m, 8H, 4xCH2-cyclohexanone), 6.91-8.02 (m, 8H, 2C6H4). 13C NMR (DMSO-d6) 5 38.55, 38.84, 39.39, 39.67, 39.95 (4-CH2, cyclohexanone), 55.5 (CH3), 116.7 (CN), 120.3, 123.6, 124.6, 125.3, 130.8, 131.1, 134.5, 136.6, 138.8, 140.6, 143.7, 146.8, 150.2 (2xC6H4, pyridine-C), 165.8 (C=N). MS (m/z) 353 (M+, 36%). 1-Methyl-3-(phenylamino)benzo[4,5]imidazo[1,2-a] pyridine-4-carbonitrile (3). To a mixture of 1 (1.57 g, 10 mmol) and acetoaceta-nilide (1.77 g, 10 mmol), ammonium acetate (0.77 g, 10 Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... Acta Chim. Slov. 2016, 63, 227-240 235 mmol) was added. The reaction mixture was heated in oil bath at 140 °C for 1 h then left to cool. The semisolid formed was triturated with ethanol (40 mL) and the formed solid product was collected by filtration and dried. The obtained product was crystallized from ethanol to give light amber crystals. Yield 2.27 g (76%); m.p. > 300 °C; Anal. Calcd. for C19H14N4 (298.34): C, 76.49; H, 4.73; N, 18.78%; found: C, 7(5.33; H, 4.44; N, 18.63%. IR (KBr) v/cm-1 3423-3106 (NH), 3056 (CH aromatic), 2955-2829 (CH-alph.), 2208 (CN), 1569, 1489 (C=C), 1526 (C=N). 1H NMR (DMSO-d6) 5 1.91 (s, 3H, CH3), 5.94 (s, 1H, pyridine C5), 7.05-7.55 (m, 9H, C6H4 C6H5), 13.19 (s, 1H, NH). 13C NMR (DMSO-d6) 5 20.24 (CH3), 116.2 (CN), 111.1, 115.9, 120.7, 120.76, 122.1, 126.2, 127.5, 128.7, 131.5, 104.2, 146.6, 150.8, 154.0, 155.1 (C6H4, C6H5, pyridine-C), 164.1 (C=N). MS (m/z) 298 (M+, 18%). 1-Methyl-2-(2-phenylhydrazono)-3-(phenylimino)-1,2, 3,4-tetrahydrobenzo-[4,5]imidazo-[1,2-a]pyridine-4-carbonitrile (4) To a cold (0-5 °C) solution of 3 (1.20 g, 40.2mmol) in ethanol (50 mL) containing sodium hydroxide solution (10 mL, 10%) and a solution of benzenediazonium chloride (40.2 mmol) [which was prepared by dissolving sodium nitrite (0.60 g, 80.4 mmol) in water (2 mL) was added to a cold solution of aniline (0.4 mL, 40.2 mmol) containing the appropriate amount of hydrochloric acid with continuous stirring] was added with continuous stirring. The reaction mixture was stirred at room temperature for 3 h and the solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give red crystals. Yield 2.67 g (66%); m.p. 245-248 °C; Anal. Calcd. for C^H^N (404.47): C, 74.24; H, 4.98; N, 20.78%; found: C, 74.05; H, 4.88; N, 19.82%. IR (KBr) v/cm-1 3419-3200 (NH), 3058 (CH aromatic), 2961-2854 (CH-alph.), 2210 (CN), 1600 (C=N), 1450 (C=C). 1H NMR (DMSO-d^ 5 1.91 (s, 3H, CH3), 5.82 (s, 1H, pyridi-ne C6), 7.17 (s,6 1H, pyridine C3),37.25-7.79 (m, 14H, QH^xQHj), 8.53 (s, 1H, NH). 13C NMR (DMSO-d^ 5 19.9 (CH3), 115.8 (CN), 118.1, 120.7, 120.7, 120.7, 121.4, 122.0, 122.9, 123.1, 123.9, 124.5, 124.9, 125.83, 126.1, 127.3, 128.7, 141.3, 156.1 (C6H4, 2xC6H5, pyridi-ne-C), 173.2, 186.9 (2xC=N). MS (m/z) 404 (M+, 66%). 2-(1-Acetyl-1_ff-benzo[d]imidazol-2(3ff)-ylidene) ace-tonitrile (5) A solution of 1 (1.57 g, 10 mmol) in acetic acid (15 mL) and acetic anhydride (35 mL) was heated under reflux till a precipitate is formed after 30 min, then poured into a beaker containing ice/water mixture. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give gold crystals. Yield 1.47 g (74%); m.p. > 300 °C; Anal. Calcd. for C11H9N3O (199.21): C, 66.32; H, 4.55; N, 21.09%; found: C, 64.48; H, 4.33; N, 21.63%. IR (KBr) v/cm-1 3069 (CH aromatic), 2965-2871 (CH-alph.), 2192 (CN), 1630 (C=O), 1594, 1410 (C=C), 1513 (C=N). 1H NMR (DM-SO-d6) 5 2.21 (s, 3H, CH3), 3.30 (s, 2H, CH2), 7.2-7.51 (m, 4H, C6H4). 13C NMR (DMSO-d6) 5 27.0 (CH3), 65.3 (CH2), 115.84 (CN), 121.1, 123.1, 124.0, 125.3, 126.0, 130.3 (C6H4), 151.1 (C=O), 189.2 (C=N). MS (m/z) 199 (M+, 49%). 2-(1-Bromo-1_ff-benzo[d]imidazol-2-yl)acetonitrile (6) A solution of 5 (1.99 g, 10 mmol) in glacial acetic acid (10 mL) was warmed to 60 oC, then bromine (0.08 g, 10 mmol) in acetic acid (10 mL) was added drop-wise with continuous stirring. The reaction mixture was stirred for 1.5 h then poured into ice/water and the solid product formed was collected by filtration. The obtained product was crystallized from ethanol to give brownish orange crystals. Yield 1.95 g (70%); m.p. > 300 °C; Anal. Calcd. for C11H8BrN3O (278.10): C, 47.51; H, 2.90; N, 15.11%; found: C, 47.33; H, 3.89; N, 13.49%. IR (KBr) v/cm-1 3050 (CH aromatic), 2971 (CH-alph.), 2193 (CN), 1630 (C=O), 1602, 1474 (C=C). 1H NMR (DMSO-d6) 5 3.30, 4.00 (2s, 4H, 2xCH2), 7.20-7.63 (m, 4H, C6H4). 63C NMR (DMSO-d6) 5 55.8, 62.7 (2xCH2), 116.46 (CN), 119.2, 121.3, 1246.8, 129.3, 133.6 (C6H4), 168.8 (C=O), 172.7 (C=N). MS (m/z) 278 (M+, 28%). 3-Amino-1-hydroxybenzo[4,5]imidazo[1,2-a]pyridine- 4-carbonitrile (7) To a solution of 6 (2.78 g, 10 mmol) in dimethylfor-mamide (5 mL) heated on a water bath at 60 °C potassium cyanide (0.65 g, 10 mmol), dissolved in a least amount of water, was added while stirring. The reaction mixture was left in the water bath for 30 min at 60 °C then poured into a beaker containing ice/water mixture and a few drops of hydrochloric acid. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give reddish brown crystals. Yield 1.93 g (86%); m.p. > 300 °C; Anal. Calcd. for C12H8N4O (224.22): C, 64.28; H, 3.60; N, 24.99%; found: C, 63.88; H, 3.88; N, 24.69%. IR (KBr) v/cm-1 3436-3233 (OH, NH2), 3050 (CH aromatic), 2193 (CN), 1513 (C=N), 1597 (C=C). 1H NMR (DMSO-d6) 5 5.21 (s, 2H, D2O exchangeable, NH2), 7.22 (s, 1H, pyridine C5), 7.21-7.88 (m, 4H, C6H4), 12.91 (s, 1H, OH). 13C NMR (DMSO-d6) 5 116.8 (CN), 119.2, 121.3, 124.8, 129.3, 133.6, 136.2, 136.8, 140.1, 142.4, 144.1, 146.7 (C6H4). MS (m/z) 224 (M+, 60%). 6 4 2-(1-(2-Hydrazinylacetyl)-1_ff-benzo[d]imidazol-2-yl) acetonitrile (8) To a solution of 6 (2.78 g, 10 mmol) in dimethylfor-mamide (5 mL) hydrazine hydrate (0.50 g, 10 mmol) was added. The reaction mixture was stirred for 3 h at room temperature then poured into a beaker containing acidi- Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... 236 Acta Chim. Slov. 2016, 63, 227-240 fied ice/water mixture. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give light brown crystals. Yield 2.01 g (88%); m.p. > 300 °C; Anal. Calcd. for C11H11N5O (229.24): C, 57.63; H, 4.84; N, 30.55%; found: C, 57.80; H, 4.69; N, 30.79%. IR (KBr) v/cm-1 3414-3214 (NH, NH2), 3100 (CH aromatic), 2900 (CH-alph.), 2194 (CN), 1668 (C=O), 1600, 1470 (C=C), 1519 (C=N). 1H NMR (DMSO-d6) 5 3.34 (s, 2H, CH2), 4.40 (s, 2H, CH2), 7.21-7.63 (m, 4H, C6H4), 5.76 (s, 2H, NH2), 12.74 (s, 1H, NH). 13C NMR (DMSO-d6) 5 56.8, 65.9 (2xch2), 120.8, 122.4, 126.7, 128.3, 133.6, 145.9 (C6H4), 164.2 (C=O), 172.8 (C=N). MS (m/z) 229 (M+, 18%). 2-(1-(2-Aminothiazol-4-yl)-1_ff-benzo[d]imidazol-2-yl) acetonitrile (9) To a solution of 6 (2.78 g, 10 mmol) in dimethylfor-mamide (20 mL), thiourea (0.76 g, 10 mmol) was added. The reaction mixture was heated under reflux for 3 h then left to cool. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give brown crystals. Yield 2.12 g (83%); m.p. > 300 °C; Anal. Calcd. for C12H9N5S (255.30): C, 56.45; H, 3.55; N, 27.43; S, 12.56%; found: C, 56.78; H, 3.69; N, 27.39; S, 12.48%. IR (KBr) v/cm-1 3428-3227 (NH2), 3050 (CH aromatic), 2967-2922 (CH-alph.), 2195 (CN), 1513 (C=N), 1597, 1474 (C=C). 1H NMR (DMSO-d6) 5 3.30 (s, 2H, CH2), 5.21 (s, 2H, NH2), 6.23 (s, 1H, thiazole C5), 7.24-7.63 (m, 4H, C6H4). 13C NMR (DMSO-d6) 5 55.6, (CH2), 116.8 (CN), 120.8, 122.4, 126.7, 128.3, 133.6, 134.3, 138.5, 145.9 (C6H4, thiazole C), 168.2, 172.8 (2xC=N). MS (m/z) 255 (M+, 25%). General procedure for the synthesis of the thiophene derivatives 11a-c To a solution of 5 (1.99 g, 10 mmol) in dimethylfor-mamide (20 mL) containing finely divided potassium hydroxide (0.56 g, 10 mmol), phenylisothiocyanate (1.35 g, 10 mmol) was added. The reaction mixture was stirred at room temperature for 24 h, then any of chloroacetone (0.92 g, 10 mmol), ethyl chloroacetate (1.22 g, 10 mmol) or a-bromoacetophenone (1.99 g, 10 mmol) was added. The whole reaction mixture was stirred at room temperature for additional 24 h. The solid product formed upon dilution with ice/water mixture containing hydrochloric acid (till pH 6) was collected by filtration and dried. The obtained product was crystallized from ethanol to give copper-coloured crystals for 11a and 11b and brown crystals for 11c. 1-(4-(1-Acetyl-1_ff-benzo[d]imidazol-2-yl)-3-amino-5-(phenylamino)thiophen-2-yl)ethanone (11a) Yield 3.36 g (86%); m.p. > 300 °C; Anal. Calcd. For C21H18N4O2S (390.46): C, 64.60; H, 4.65; N, 14.35; S, 8.21%; found: C, 64.88; H, 4.67; N, 14.72; S, 8.40%. IR (KBr) v/cm-1 3456-3210 (NH), 3064 (CH aromatic), 2966-2875 (CH-alph.), 2192 (CN), 1730 (C=O), 1598, 1470 (C=C), 1516 (C=N). 1H NMR (DMSO-d6) 5 1.84, 1.89 (2s, 6H, 2xCH3), 5.48 (s, 2H, NH2), 7.12-7.51 (m, 9H, C6H4 C6H5), 12.71 (s, 1H, NH). 13C NMR (DMSO-d6) 5 27.0 (CH3), 38.8 (CH2), 115.8 (CN), 121.4, 123.1, 1244.9, 125.1, 126.2, 127.9, 128.2, 129.4, 130.3, 133.2, 134.8, 136.8, 140.2, 142.1 (C6H4, C6H5, thiophene C), 163.8, 166.2 (2 C=O), 182.5 (C=N). MS (m/z) 390 (M+, 38%). Ethyl 4-(1-acetyl-1_ff-benzo[d]imidazol-2-yl)-3-amino-5-(phenylamino)-thiophene-2-carboxylate (11b) Yield 2.94 g (70%); m.p. 140 °C; Anal. Calcd. for C22H20N4O3S (420.48): C, 62.84; H, 4.79; N, 13.32; S, 7.63%; found: C, 62.73; H, 4.52; N, 13.06; S, 7.67%. IR (KBr) v/cm-1 3441-3211 (NH), 3063 (CH aromatic), 2970-2876 (CH-alph.), 2193 (CN), 1725 (C=O), 1597, 1472 (C=C), 1516 (C=N). 1H NMR (DMSO-d6) 5 1.16-1.21 (t, 3H, CH3), 2.11 (s, 3H, CH3), 3.97 (s, 2H, NH2), 4.11-4.16 (q, 2H, CH2), 6.76-7.55 (m, 9H, C6H4 C6H5), 12.74 (s, 1H, NH). 13C NMR (DMSO-d6) 5 16.3 (ester CH3), 28.2 (CO-CH3), 52.8 (ester CH2), 115.9 (CN), 120.6, 122.8, 123.4, "125.0, 125.8, 126.3, 126.8, 128.1, 130.3, 133.4, 136.1, 138.9, 141.8, 142.0 (C6H4, C6H5, thiophene C), 164.3, 166.9 (2xC=O), 172.8 (C=N). M6S (5m/z) 420 (M+, 26%). 1-(2-(4-Amino-5-benzoyl-2-(phenylamino)thiophen-3-yl)-1ff-benzo[d]imidazol-1-yl)ethanone (11c) Yield 2.26 g (50%); m.p. > 300 °C; Anal. Calcd. for C26H20N4O2S (452.53): C, 69.01; H, 4.45; N, 12.38; S, 7.2069%20; f4ou2nd: C, 68.89; H, 4.65; N, 12.09; S, 6.83%. IR (KBr) v/cm-1 3431-3212 (NH, NH2), 3067 (CH aromatic), 2968-2879 (CH-alph.), 2195 (CN), 1690, 1627 (2 C=O), 1599, 1471 (C=C), 1516 (C=N). 1H NMR (DMSO-d6) 5 2.12 (s, 3H, CH3), 2.73 (s, 2H, D2O exchangeable, NH2), 7.21-8.09 (m, 14H, C6H4, 2xC6H5), 8.74 (s, 1H, D20 exchangeable, NH). 13C NMR (DMSO-d6) 5 28.6 (CO-CllJ, 119.3, 121.9, 124.2, 125.8, 125.8, 126.0, 126.8, 1227.1, 127.9, 128.1, 130.3, 133.4, 136.1, 138.9, 140.3, 141.2, 142.6, 143.8 (2xC6H5, thiophene C), 163.9, 165.2 (2xC=O), 170.6 (C=N). MS (m/z) 452 (M+, 42%). General procedure for the synthesis of the benzylidene derivatives 12a,b To a solution of 5 (1.99 g, 10 mmol) in dimethylfor-mamide (25 mL) containing piperidine (0.5 mL), either of benzaldehyde (1.06 g, 10 mmol) or salicylaldehyde (1.22 g, 10 mmol) was added. The reaction mixture was heated under reflux for 3 h then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product formed was collected by filtration and dried. The obtained product was crystallized from et-hanol to give yellow crystals of 12a and orange crystals of 12b. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... Acta Chim. Slov. 2016, 63, 227-240 237 2-(1-Acetyl-1_ff-benzo[d]imidazol-2-yl)-3-phenylacry-lonitrile (12a) Yield 1.81 g (63%); m.p. > 300 °C; Anal. Calcd. for C18H13N3O (287.32): C, 75.25; H, 4.56; N, 14.63%; found: C, 74.33; H, 4.36; N, 14.49%. IR (KBr) v/cm-1 3066 (CH aromatic), 2967-2876 (CH-alph.), 2193 (CN), 1627 (C=O), 1599, 1470 (C=C), 1515 (C=N). 1H NMR (DMSO-d6) 5 2.00 (s, 3H, CH3), 3.30 (s, 1H, CH), 7.21-7.51 (m, 9H, C6H4 C6H5). 13C NMR (DMSO-d6) 5 28.4 (CO-CH3), 88.5, 90.6 (CH=C), 121.6, 123.8, 124.2, 124.9, 125.03, 127.1, 130.3, 133.4, 138.9, 139.0 (2xC6H5), 165.8 (C=O), 171.2 (C=N). MS (m/z) 287 (M+, 23%). 2-(1-Acetyl-1ff-benzo[d]imidazol-2-yl)-3-(2-hydroxyp-henyl)acrylonitrile (12b) Yield 2.79 g (92%); m.p. > 300 °C; Anal. Calcd. for C18H13N3O2 (303.31): C, 71.28; H, 4.32; N, 13.85%; found: C, 71.33; H, 4.88; N, 9.04%. IR (KBr) v/cm-1 3432-3215 (OH), 3100 (CH aromatic), 2999-2882 (CH-alph.), 2194 (CN), 1633 (C=O), 1601, 1477 (C=C), 1518 (C=N). 1H NMR (DMSO-d6) 5 1.20 (s, 3H, CH3), 3.57 (s, 1H, CH), 7.21-7.51 (m, 8H, 2C6H4), 12.75 (s, 1H, D2O exchangeable, OH). 13C NMR (DMSO-d6) 5 28.6 (CO-CH3), 88.9, 90.8 (CH=C), 120.8, 122.5, 124.2, 124.6, 125.6, 126.8, 128.7, 133.4, 136.3, 140.3 (2xC6H5), 164.6 (C=O), 170.8 (C=N). MS (m/z) 303 (M+, 36%). General procedure for the synthesis of the ben-zo[4,5]imidazo[1,2-a]pyridine derivatives 13a,b To a solution of 5 (1.99 g, 10 mmol) in dimethylfor-mamide (30 mL) containing triethylamine (0.5 mL), either malononitrile (0.66 g, 10 mmol) or ethyl cyanoacetate (1.13 g, 10 mmol) was added. The reaction mixture was heated under reflux for 4 h then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give buff crystals of 13a and yellowish brown crystals of 13b. 3-Amino-1-methylbenzo[4,5]imidazo[1,2-a]pyridine-2,4-dicarbonitrile (13a) Yield 2.04 g (82%); m.p. > 300 °C; Anal. Calcd. For C14H11N5 (249.27): C, 67.46; H, 4.45; N, 28.10%; found: C, 67.06; H, 4.18; N, 28.43%. IR (KBr) v/cm-1 3470-3212 (NH, NH2), 3077 (CH aromatic), 2971-2877 (CH-alph.), 2223, 2194 (2CN), 1599, 1474 (C=C), 1517 (C=N). 1H NMR (DMSO-d6) 5 1.16 (s, 3H, CH3), 5.51 (s, 2H, D2O exchangeable, NH2), 6.30 (s, 1H, pyridine C6), 7.21-7.50 (m, 4H, C6H4), 12.75 (s, 1H, NH). 13C NMR (DMSO-d6) 5 22.7 (CH3), 116.8, 117.3 (2xCN), 119.8, 120.7, 122.5, 124.8, 125.3, 126.4, 128.0, 130.9, 133.2, 134.8, 143.2 (C6H4, imidazole, pyridine C), 173.8 (C=N). MS (m/z) 249 (M+, 22%). Ethyl 3-amino-4-cyano-1 -methylbenzo[4,5]imidazo [1,2-a]pyridine-2-carboxylate (13b) Yield 2.01 g (68%); m.p. > 300 °C; Anal. Calcd. for C16H16N4O2 (296.32): C, 64.85; H, 5.44; N, 18.91%; found: C, 64.92; H, 4.27; N, 18.73%. IR (KBr) v/cm-1 3426-3214 (NH, NH2), 3103 (CH aromatic), 2883 (CH-alph.), 2194 (CN), 1750 (C=O, ester), 1601, 1472 (C=C). 1H NMR (DMSO-d6) 5 1.10 (t, 3H, CH3), 2.12 (s, 3H, CH3), 3.29 (q, 2H, CH2), 5.01 (s, 2H, D20 exchangeable, NH2), 6.10 (s, 1H, pyridine C6), 7.20-7.51 (m, 4H, C6H4), 12.773 (s, 1H, D2O exchangeable, NH). 13C NMR (DMSO-d6) 5 16.8 (ester CH3), 22.4 (CH3), 56.9 (ester CH2), 116.5, 117.1 (2xCN), 119.9, 121.3, 122.8, 124.4, 125.1, 126.8, 127.4, 130.3, 133.6, 134.1, 143.8 (C6H4, imidazole, pyridine C), 162.8 (C=O). MS (m/z) 296 (M+, 35%). 2-(1-Acetyl-1_ff-benzo[d]imidazol-2-yl)-3-phenylbut-2-enenitrile (14) To a mixture of 5 (1.99 g, 10 mmol) and acetophe-none (1.35 g, 10 mmol), ammonium acetate (0.77 g, 10 mmol) was added. The reaction mixture was heated in oil bath at 140 °C for 1 h then left to cool. The semisolid formed was triturated with ethanol (40 mL) and the formed solid product was collected by filtration and dried. The obtained product was crystallized from ethanol to give dark brown crystals. Yield 1.99 g (66%); m.p. 210-213 °C; Anal. Calcd. for C19H15N3O (301.34): C, 75.73; H, 5.02; N, 13.94%; found: C, 74.83; H, 5.39; N, 13.85%. IR (KBr) v/cm-1 3086 (CH aromatic), 2880 (CH-alph.), 2194 (CN), 1630 (C=O), 1599, 1472 (C=C), 1517 (C=N). 1H NMR (DMSO-d6) 5 1.20, 2.40 (2s, 6H, 2xCH3), 7.21-7.52 (m, 9H, C6H4 C6H5). 13C NMR (DMSO-d6) 5 22.4, 28.6 (CH3, CO-CH3), 88.9, 90.6 (CH=C), 121.3, 122.5, 124.2, 124.63, 126.1, 126.8, 127.2, 133.4, 136.3, 136.9 (2xC6H5), 164.6 (C=O), 170.6 (C=N). MS (m/z) 301 (M+, 17%). 2-(1-Acetyl-1_ff-benzo[d]imidazol-2-yl)-3,5-diphenyl-penta-2,4-dienenitrile (15) To a solution of 14 (3.01 g, 10 mmol) in dimethyl-formamide (25 mL) containing piperidine (0.50 mL), benzaldehyde (1.06 g, 10 mmol) was added. The reaction mixture was heated under reflux for 4 h then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give brown crystals. Yield 2.57 g (66%); m.p. 150 °C; Anal. Calcd. for C26H19N3O (389.45): C, 80.18; H, 4.92; N, 10.79%; found: C, 80.29; H, 5.14; N, 10.59%. IR (KBr) v/cm-1 3057 (CH aromatic), 2927 (CH-alph.), 2195 (CN), 1627 (C=O), 1596 (C=N), 1489 (C=C). 1H NMR (DMSO-d6) 5 2.23 (s, 3H, CH3), 2.72, 2.89 (2s, 2H, 2xCH), 6.50-86.35 (m, 14H, C6H4 2xC6H5). 13C NMR (DMSO-d6) 5 24.3 (CH3), 98.5, 104.8 (C=C), 116.4 (CN), 120.^4, 121.3, 122.4, 124.9, 125.8, 126.8, 127.8, 128.0, 130.6, 133.5, Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... 238 Acta Chim. Slov. 2016, 63, 227-240 136.5, 140.8 (C6H4, 2xc6h5), 164.3 (C=O), 173.1 (C=N). MS (m/z) 389 (M+, 44%). General procedure for the synthesis of the thiophene derivatives 16a,b To a solution of 5 (1.99 g, 10 mmol) in 1,4-dioxane (25 mL) containing triethylamine (0.50 mL) and elemental sulfur (0.32 g, 10 mmol) either malononitrile (0.66 g, 10 mmol) or ethyl cyanoacetate (1.13 g, 10 mmol) was added. The reaction mixture was heated under reflux for 4 h then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product was collected by filtration and dried. The obtained product was crystallized from ethanol to give dark brown crystals of 16a and light brown crystals of 16b. 5-(1-Acetyl-1_ff-benzo[d]imidazol-2-yl)-2,4-diaminot-hiophene-3-carbonitrile (16a) Yield 2.08 g (70%); m.p. 288-293 °C; Anal. Calcd. for C14H11N5OS (297.34): C, 56.55; H, 3.73; N, 23.55; S, 10.78%; found: C, 56.43; H, 3.49; N, 23.70; S, 10.63%. IR (KBr) v/cm-1 3426-3213 (2xNH2), 3050 (CH aromatic), 2973, 2882 (CH-alph.), 2195 (CN), 1680 (C=O), 1600 (C=N), 1470 (C=C), 1518 (C=N). 1H NMR (DMSO-d6) 5 2.06 (s, 3H, CH3), 2.73, 2.89 (2s, 4H, D2O exchangeable, 2xNH2), 7.20-73.95 (m, 4H, C6H4). 13C NMR (DMSO-d6) 5 22.6 (CH3), 116.3 (CN), 119.8, 120.7, 122.6, 124.6, 129.5, 130.4, 133.5, 142.8, 143.2, 144.3 (C6H4, thiophene C), 163.2 (C=O), 172.3 (C=N). MS (m/z) 297 (M+, 32%). Ethyl 5-(1-acetyl-1_ff-benzo[d]imidazol-2-yl)-2,4-dia-minothiophene-3-carboxylate (16b) Yield 2.38 g (69%); m.p. > 300 °C; Anal. Calcd. for C16H16N4O3S (344.39): C, 55.80; H, 4.68; N, 16.27; S, 9.31%; found: C, 55.89, H, 4.29; N, 16.60; S, 8.04%. IR (KBr) v/cm-1 3430-3216 (2 NH2), 3107 (CH aromatic), 2978, 2884 (CH-alph.), 1633 (C=O), 1750 (C=O, ester), 1601 (C=N), 1471 (C=C), 1518 (C=N). 1H NMR (DMSO-d6) 5 1.04 (t, 3H, CH3), 2.33 (s, 3H, CH3), 4.28 (q, 2H, CH2), 5.80, 5.95 (2s, 4H, D2O exchangeable, 2 NH2), 7.21-7.51 (m, 4H, C6H4). 13C NMR (DMSO-d6) 5 16.22 (ester CH3), 22.8 (CH3), 120.3, 120.8, 121.2, 123.8, 124.8, 125.8, 134.8, 142.8, 143.6, 144.9 (C6H4, thiophene C), 164.8 (C=O), 172.0 (C=N). MS (m/z) 344 (M+, 48%). 2-(2-Phenylhydrazono)-2-(1-acetyl-1_ff-benzo[d]imida-zol-2-yl) acetonitrile (17) To a cold solution (0-5 oC) of 5 (1.99 g, 10 mmol) in ethanol (50 mL) containing sodium hydroxide solution (10 mL, 10%) and a solution of benzenediazonium chloride (10 mmol) [which was prepared by dissolving sodium nitrite (0.70 g, 10 mmol) in water, 2 mL was added to a cold solution of aniline (0.93 g, 10 mmol) containing appropriate amount of hydrochloric acid and with continuous stirring] was added with continuous stirring. The solid product formed was collected by filtration and dried. The obtained product was crystallized from ethanol to give brown crystals. Yield 2.24 g (74%); m.p. 265 °C; Anal. Calcd for C17H13N5O (303.32): C, 67.32; H, 4.32; N, 23.09%; found: C, 67.29; H, 4.09; N, 23.27%. IR (KBr) v/cm-1 3423-3214 (NH), 3098 (CH aromatic), 2976-2883 (CH-alph.), 2194 (CN), 1631 (C=O), 1521 (=N-NH), 1601, 1475 (C=C). 1H NMR (DMSO-d6) 5 2.21 (s, 3H, CH3), 7.21-7.51 (m, 9H, C6H4, C6H5), 12.76 (s, 1H, D2O exchangeable, NH). 13C NMR (DMSO-d6) 5 22.8 (CH3), 115.9 (CN), 120.4, 120.7, 123.2, 124.6, 126.5, 128.6, 133.5, 142.8, 143.2, 144.3 (C6H5, C6H4), 164.0 (C=O), 172.8 (C=N). MS (m/z) 303 (M+, 20%). General procedure for the synthesis of the phenylhy-drazone derivatives 18a,b To a solution of 17 (3.03 g, 10 mmol) in 1,4-dioxane (30 mL) containing triethylamine (0.50 mL) and elemental sulfur (0.32 g, 10 mmol) either malononitrile (0.66 g, 10 mmol) or ethyl cyanoacetae (1.13 g, 10 mmol) was added. The reaction mixture was heated under reflux for 4 h then poured into a beaker containing ice/water mixture containing a few drops of hydrochloric acid. The solid product was collected by filtration and dried. The obtained product was crystallized from ethanol to give yellow crystals of 18a and light green crystals of 18b. 4-(2-((2-Phenylhydrazono)(cyano)methyl)-1_ff-benzo [d]imidazol-1-yl)-2-aminothiophene-3-carbonitrile (18a) Yield 3.45 g (90%); m.p. 198 °C; Anal. Calcd. for C20H13N7S (383.43): C, 62.65; H, 3.42; N, 25.57; S, 8.36%; found: C, 62.88; H, 3.59; N, 25.19; S, 8.07%. IR (KBr) v/cm-1 3352-3209 (NH, NH2), 3100 (CH-aroma-tic), 2922 (CH-alph.), 2196 (CN), 1547 (C=N), 1463 (C=C). 1H NMR (DMSO-d6) 5 5.60 (s, 2H, D2O exchangeable, NH2), 7.20 (s, 1H, thiophene C5), 7.21-7.67 (m, 9H, C6H4 C6H5), 12.75 (s, 1H, NH). 13C NMR (DMSO-d6) 5 116.3. 116.8 (2xCN), 120.0, 120.6, 123.2, 125.1, 126.5, 127.2, 136.5, 138.1, 139.2, 140.6, 140.8, 141.3, 142.6 (C6H5, C6H4, thiophene C), 164.0 (C=O), 172.8 (C=N). MS 5m/z) 383 (M+, 18%). Ethyl 4-(2-((2-phenylhydrazono)(cyano)methyl)-1_ff-benzo[d]imidazol-1-yl)-2-aminothiophene-3-carboxy-late (18b) Yield 2.54 g (59%); m.p. > 300 °C; Anal. Calcd. for C22H18N6O2S (430.48): C, 61.38; H, 4.21; N, 19.52; S, 7.2425%18; f6ou2nd: C, 61.03; H, 4.58; N, 19.71; S, 7.66%. IR (KBr) v/cm-1 3427-3215 (NH, NH2), 3100 (CH aromatic), 2900 (CH-alph.), 2194 (CN), 1632 (C=O), 1520 (C=N), 1601, 1475 (C=C). 1H NMR (DMSO-d6) 5 1.10 (t, 3H, CH3), 4.21 (q, 2H, CH2), 5.01 (s, 2H, D2O exchangeable, NH2), 7.20 (s, 1H, thiophene C5), 7.21-7.51 (m, 9H, C6H4, C6H5), 12.77 (s,1H, D2O exchangeable, NH). 13C NMR (I6MSO-d6) 5 16.3 (ester CH3), 54.8 (ester Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... Acta Chim. Slov. 2016, 63, 227-240 239 CH2), 116.5 (CN), 120.3, 121.8, 123.8, 125.1, 127.2, 128.6, 130.2, 138.1, 139.2, 139.9, 140.4, 142.9, 143.8 (C6H5, C6H4, thiophene C), 164.0 (C=O), 172.8 (C=N). MS (m/z) 430 (M+, 22%). 5. Conclusions In the present study we have synthesized a series of heterocyclic derivatives of 2-cyanomethylbenzo[c]imida-zole 1. The newly synthesized products were tested against MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), and SF-268 (CNS cancer) and the results showed that compounds 2b, 6, 11b, 11c, 12b, 16a, 16b and 18a exhibited optimal cytotoxic effect against cancer cell lines. The toxicity of these optimal cytotoxic compounds was monitored via in vivo lethality to shrimp larvae (Arte-mia salina). The results showed that compounds 11b, 12b, and 16b are non toxic towards shrimp larvae. 6. References 1. H. Irannejad, M. Amini, F. Khodagholi, N. Ansari, S. K. Tu-si, M. Sharifzadeh, A. Shafiee, Bioorg. Med. Chem. 2010, 18, 4224-4230. http://dx.doi.org/10.1016/j.bmc.2010.04.097 2. N. Catozzi, M. G. Edwards, S. A. Raw, P. Wasnaire, R. K. Taylor, J. Org. Chem. 2009, 74, 8343-8354. http://dx.doi.org/10.1021/jo901761r 3. S. Laphookhieo, S. Jones, S. A. Raw, Y. F. Sainz, R. J. K. Taylor, Tetrahedron Lett. 2006, 47, 3865-3870. http://dx.doi.org/10.1016/j.tetlet.2006.03.178 4. D. L. Boger, J. S. Panek, M. Yasuda, Org. Synth. 1988, 66, 142-150. http://dx.doi.org/10.15227/orgsyn.066.0142 5. R. M. Mohareb, K. El-Sharkawy, S. M. Sherif, Acta Pharm. 2008, 58, 429-444. 6. A. M. Salah, Heteroatom Chem. 2003, 14, 612-614. http://dx.doi.org/10.1002/hc.10199 7. P. A. Crooks, L. P. Dwoskin, Biochemical Pharmacology 1997, 54, 743-753. http://dx.doi.org/10.1016/S0006-2952(97)00117-2 8. B. K. Warren, E. E. Knaus, Eur. J. Med. Chem. 1987, 22, 411-415. http://dx.doi.org/10.1016/0223-5234(87)90028-6 9. B. J. Mulchin, C. G. Newton, J. W. Baty, C. H. Grasso, W. J. Martin, M. C. Walton, E. M. Dangerfield, C. H. Plunkett, M. V. Berridge, J. L. Harper, M. S. Timmer, B. L. Stocker, Bioorg. Med. Chem. 2010, 18, 3238-3251. http://dx.doi.org/10.1016/j.bmc.2010.03.021 10. Y.-L. Luo, K. Baathulaa, V. K. Kannekanti, C.-H. Zhou, G.-X. Cai, Sci. China Chem. 2015, 58, 483-494. http://dx.doi.org/10.1007/s11426-014-5296-3 11. J. N. Sangshetti, P. P. Dharmadhikari, R. S. Chouthe, B. Fa-tema, V. Lad, V. Karande, S. N. Darandale, D. B. Shinde, Bi-oorg. Med. Chem. Lett. 2013, 23, 2250-2253. http://dx.doi.Org/10.1016/j.bmcl.2013.01.041 12. J. Witherington, V. Bordas, S. L. Garland, D. M. B. Hickey, R. J. Ife, J. Liddle, M. Saunders, D. G. Smith, R. W. Ward, Bioorg. Med. Chem. Lett. 2003, 13, 1577-1580. http://dx.doi.org/10.1016/S0960-894X(03)00134-3 13. X.-H. Liu, H.-F. Liu, X. Shen, B.-A. Song, P. S. Bhadury, H.-L. Zhu, J.-X. Liu, X.-B. Qi, Bioorg. Med. Chem. Lett. 2010, 20, 4163-4167. http://dx.doi.org/10.1016/j.bmcl.2010.05.080 14. S. Ram, Progress in Medicinal Chemistry 1988, 25, 233-247. http://dx.doi.org/10.1016/S0079-6468(08)70279-0 15. M. Gaba, S. Singh, C. Mohan, Eur. J. Med. Chem. 2014, 76, 494-505. http://dx.doi.org/10.1016Zj.ejmech.2014.01.030 16. Y. M. Shaker, M. A. Omar, K. Mahmoud, S. M. Elhallouty, W. M. El-Senousy, M. M. Ali, A. E. Mahmoud, A. H. Abdel-Halim, S. M. Soliman, H. I. El Diwani, J. Enzyme Inhib. Med. Chem. 2015, 8, 1-20. 17. J. J. B. Nevado, G. C. Penalvo, R. M. R. Dorado, V. R. Robledo, J. Pharm. Biomed. Anal. 2014, 92, 211-219. http://dx.doi.org/10.1016/jjpba.2013.12.020 18. S. Fujimoto, Eur. J. Pharm. 1994, 265, 159-166. http://dx.doi.org/10.1016/0014-2999(94)90426-X 19. A. D. Khoje, C. Charnock, B. Wan, S. Franzblau, L.-L. Gun-dersen, Bioorg. Med. Chem. 2011, 19, 3483-3491. http://dx.doi.org/10.1016/j.bmc.2011.04.023 20. D. Seenaiah, P. R. Reddy, G. M. Reddy, A. Padmaja, V. Pad-mavathi, N. S. Krishna, Eur. J. Med. Chem. 2014, 77, 1-7. http://dx.doi.org/10.1016/j.ejmech.2014.02.050 21. E. C. Herrmann, J. A. Herrmann, D. C. Delong, Antiviral Research, 1981, 1, 301-314. http://dx.doi.org/10.1016/0166-3542(81)90022-X 22. S. Sharma, S. Gangal, A. Rauf, Eur. J. Med. Chem. 2009, 44, 1751-1757. http://dx.doi.org/10.1016/j.ejmech.2008.03.026 23. M. Rashid, A. Husain, R. Mishra, Eur. J. Med. Chem. 2012, 54, 855-866. http://dx.doi.org/10.1016/j.ejmech.2012.04.027 24. R. S. Harapanhalli, R. W. Howell, D. V. Rao, Nuclear Med. Biol. 1994, 21, 641-647. http://dx.doi.org/10.1016/0969-8051(94)90030-2 25. S. Singh, B. S. Dwarakanath, T. L. Mathew, J. Phtotochem. Photobiol. B. 2004, 77, 45-54. http://dx.doi.org/10.1016/S1011-1344(04)00122-8 26. H. A. S. Elzahabi, Eur. J. Med. Chem. 2011, 46, 4025-4034. http://dx.doi.org/10.1016/j.ejmech.2011.05.075 27. J. R. Tseng, D. Stuart, K. Aardalen, A. Kaplan, N. Aziz, N. P. Hughes, S. S. Gambhir, Neoplasia 2011, 13, 266-275. http://dx.doi.org/10.1593/neo.101466 28. T. R. Reddy, G. R. Reddy, L. S. Reddy, S. Jammula, Y. Lin-gappa, R. Kapavarapu, C. L. Meda, K. V. Parsa, M. Pal, Eur. J. Med. Chem. 2012, 48, 265-274. http://dx.doi.org/10.1016/j.ejmech.2011.12.024 29. S. Khaksar, M. Yaghoobi, J. Fluor. Chem. 2012, 142, 41-44. http://dx.doi.org/10.1016/jjfluchem.2012.06.009 30. R. M. Mohareb, S. M. Sherif, Arch. Die Pharm. (Weinheim), 1991, 324, 469-471. http://dx.doi.org/10.1002/ardp.2503240801 Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... 240 Acta Chim. Slov. 2016, 63, 227-240 31. R. M. Mohareb, N. I. Abdel-Sayed, S. M. Sherif, Phosphorus, Sulfur, Silicon Relat. Elem. 1991, 63, 119-129. http://dx.doi.org/10.1080/10426509108029435 32. R. M. Mohareb, Monatsh. Chem. 1992, 123, 341-347. http://dx.doi.org/10.1007/BF00810946 33. J. Chodosh, R. D. Dix, R. C. Howell, W. G. Stroop, S. C. G. Tseng, Invest. Ophthalmol. Vis. Sci. 1994, 35, 1046-1058. 34. A. U. Rahman, M. I. Choudhary, W. J. Thomsen, Bioassay Techniques for Drug Development, Harwood Academic, Amsterdam, The Netherlands, 2001. http://dx.doi.org/10.4324/9780203304532 35. B. Brayn, M. Timothy, S. Tore, General and Applied Toxicology, 2nd ed., vol. I, 52 p. 36. J. L. Carballo, Z. L. H. Inda, P. Pérez, M. D. G. Grávalos, BMC Biotechnol. 2002, 2, 17-22. http://dx.doi.org/10.1186/1472-6750-2-17 37. M. Calleja, G. Persoone, Atla. 1992, 20, 396-405. 38. P. N. Chatterjee, S. Roy, Tetrahedron 2011, 67, 4569-4577. http://dx.doi.org/10.1016Zj.tet.2011.04.092 Povzetek Pri reakciji etil cianoacetat z o-fenilendiaminom je nastal 2-cianometilbenzo[c]imidazol (1). To spojino smo uporabili kot ključno izhodno snov za sintezo biološko aktivnih heterocikličnih derivatov. Pri reakciji 1 s cikloheksanonom ter benzaldehidom, 4-metoksibenzaldehidom oz. 4-klorobenzaldehidom so nastali pripojeni derivati 2a-c. Testiranje anti-tumorske aktivnosti novopripravljenih produktov proti trem rakastim celičnim linijam, t.j. MCF-7 (adeno-carcinom dojke), NCI-H460 (nemikrocelični karcinom pljuč) in SF-268 (rak centralnega živčnega sistema), je pokazalo, da spojine 2b, 6, 11b, 11c, 12b, 16a, 16b in 18a kažejo optimalno citotoksično učinkovitost proti tem rakastim linjam z IC50 vrednostmi v nM območju. Ker so bioaktivne spojine pogosto strupene za ličinke morskih rakcev, smo se odločili preveriti še in vivo strupenost teh spojin na ličinke Artemia salina. Spojine 11b, 12b in 16b niso pokazale nobene strupenosti za testirane organizme. Mohareb et al.: New Approaches for the Synthesis, Cytotoxicity ... DOI: 10.17344/acsi.2015.1927 Acta Chim. Slov. 2016, 63, 241-250 241 Scientific paper DFT Studies of NH-Cl Hydrogen Bond of Amino Acid Hydrochloride Salts in Ion Channels Marjan Moridi,1 Setareh Shekarsaraei1 and Nasser L. Hadipour1* 1 Department of Chemistry, Tarbiat Modares University, Tehran, Iran * Corresponding author: E-mail: hadipour@modares.ac.ir Phone: (+886)2 27898679 Received: 22-08-2015 Abstract Quantum chemical calculations were made, to study NH-Cl hydrogen bonds of two amino acid hydrochloride salts called alanine and threonine. The Nuclear Magnetic Resonance and Nuclear Quadrupole Resonance parameters for nitrogen and chlorine were calculated via four functionals such as, B3LYP, M062X, M06L, and CAM-B3LYP and by applying the 6-311++G(d,p) basis set. One of the functionals produced more accurate results. Geometry optimization was performed using the M062X/6-31++G(d,p) method, and Natural Bond Orbitals analysis was performed by applying the M062X/6-311++G(d,p) level. This study examined Nuclear Magnetic Resonance and Nuclear Quadrupole Resonance parameters with changes in structure from monomer to pentamer and investigated correlations between Natural Bond Orbitals parameters and Nuclear Magnetic Resonance or Nuclear Quadrupole Resonance parameters. The Natural Bond Orbitals parameters were used to investigate changes in structural parameters along with crystal development. Keywords: Chemical shift; Quadrupolar coupling constant; Nuclear magnetic resonance; Density functional theory. 1. Introduction Properties of the hydrogen bond are well known because it has been the subject of many investigations.1-6 Hydrogen bonds have an important role in biological sys-tems7 and in the determination of structures and properties of large molecules in biochemistry, chemistry, and materials science.8-12 The detection of molecular structure in Ion Channels is possible by studying the hydrogen bonds. Ami-no acids are components of ion channels. These channels that are located in cell membranes guide electrical current through the membrane.13-15 Ion channels play a major role in biological processes and when defective can cause significant health problems such as Bartter's syndrome, cystic fibrosis, startle disease, and myotonia.13 For example, a defect in alanine, histidine, threonine, aspartic acid, and cysteine amino acids leads to mutation or change in CLCNKBa ion channel that causes type iii of Bartter's syndrome.16 Thus, the study of the structural and binding environments of inorganic atoms within these channels has important implications. The knowledge of the structure of these channels can be increased by studying the hydrogen bonds. Thus, the aim of the study of interactions in amino acids is to determine any change in structure to recognize any defects in these channels. Most information regarding the structure of ion channels has been obtained by X-ray crystallography,17,18 but in this study, the goal is to evaluate any changes in the structure of these channels by using solid-state nuclear magnetic resonance (SSNMR) and nuclear quadrupole resonance (NQR).19 In general, the study of biological molecules, such as proteins, use the NMR spec-troscopy technique that is beneficial for determining structure in both the solution20,21 and solid states.22,23 Solid-state NMR has been considered a lot over the past several deca-des,24,25 including studies on proteins,26 polymers, inorganic materials,27 as well as clays and minerals.28 More accurate information can be obtained by using NQR data in addition to NMR data.29 We can understand any changes in a The CLCNKB gene belongs to the CLC family of genes, which provide instructions for making chloride channels. These channels, which transport negatively charged chlorine atoms (chloride ions), play a key role in a cell's ability to generate and transmit electrical signals. Some CLC channels regulate the flow of chloride ions across cell membranes, while others transport chloride ions within cells. The CLCNKB gene provides instructions for making a chloride channel called ClC-Kb. The official name of this gene is »chloride voltage-gated channel Kb.« CLCNKB is the gene's official symbol. Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid 242 Acta Chim. Slov. 2016, 63, 241-250 the nuclear environment with changes in NMR and NQR parameters and thus find any changes in the structure of amino acids. In this study, we also find the most accurate functional from B3LYP, M062X, M06L, and CAM-B3LYP30 to calculate NMR and NQR parameters. M062X is very convenient to use in biological structures, and M06L has produced highly accurate results in such systems.31,32 1. 1. NMR Tensor Convention In SSNMR, we have to calculate chemical shielding tensor parameters to obtain information about interactions. In Haeberlen-Mehring-Spiess (HMS) conven-tion,33,34 three NMR parameters can be calculated by using three principal components of the chemical shielding tensor, oXX, oYY and a7Z. The relationship between three principal components of the chemical shielding tensor must always be as follows: |aZZ - oiso|> |oXX - oiso|> |oYY - oiso|. The NMR parameters defined below: (1) (2) (3) where oiso is the isotropic shielding value, Ao is the shielding tensor anisotropy, and n is shielding tensor asymmetry, which must always have a value between zero and one. 1. 2. Nuclear Electric Quadrupolar Interaction Nuclei with nuclear spin quantum number (I) larger than 1/2, are quadrupolar nuclei. For these nuclei, the electric charge is not spherically symmetrical, and they have an electric quadrupole moment, Q. The electrostatic field gradient tensor (EFG) arising from the electron distribution, and it will couple with Q at the nuclear center, so these nuclei can be studied by NQR spectroscopy. Principal components of EFG tensor must be arranged in this way: q^ > qYY > q^. The quadrupolar coupling constant (Cq) and the asymmetry parameter (^), represent the magnitude of quadrupole interaction and the symmetry around the nucleus, respectively, where e is the charge on an electron, Q is the nuclear electric quadrupole moment, and h is Planck's constant: (4) (5) The other aim of this study was to show the correlation between the structural parameters and Natural Bond Orbitals (NBO) data. Analysis of the hydrogen bonding was required to achieve this goal. The A-H-B hydrogen bond is a combination of two effects:35 (1) The hyperco-njugative effect that decreases the strength of the A-H bond thereby increasing the length of the A-H bond. This effect is the electron charge transfer from the lone pair of the Lewis base, B, to the antibonding orbital, o*, of the A-H bond. This interaction, nB ^ oAH*, can be calculated as the second-order perturbation theory energy (Eq. (6)):36 Ejvbo = B<2> =AE(nE , -, _ -2Z (6) AH «C°iH)-ïCnu) where < nB|F|oAH* > is the Fock matrix element, and e(oAH*)-e(nB) is the energy difference between these two orbitals. (2) The rehybridization effect that leads to an increase in A-H bond strength also decreases the A-H bond length. This effect is a concept of Bent's rule, which speaks to the hybridization of the central atom (A) in the molecule X-A-Y. A provides hybridized atomic orbitals that form A's part of its bond to X and to Y. Bent's rule says that as we change the electronegativity of X and/or Y, A will tend to rehybridize its orbitals such that more s character will be placed in those orbitals and be directed towards the more electropositive substituent.37 2. Methods Calculations of molecular orbital were carried out using the density functional theory (DFT) method. All Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid Acta Chim. Slov. 2016, 63, 241-250 243 Figure 2. Hydrogen-bonding network of alanine hydrochloride cluster optimized at M06-2X / 6-31++G(d,p) level. DFT calculations were performed using the GAMESS electronic structure package.38 Alanine hydrochloride atomic coordinates and unit cell parameters were derived from X-ray or neutron diffraction studies of Di Blasio et al.,39 while threonine hydrochloride atomic coordinates from the X-ray structures of L. Bryce et al.25 were used. The geometry optimizations were performed using M06-2X method with 6- 31++G(d,p) basis set to find the position of hydrogen atoms in the stable state of the system from monomer to pentamer in threonine hydrochloride (Figure 1) and alanine hydrochloride (Figure 2). Reports show that this method is more accurate for matching to experimental data.30 The models closely approximate the real crystal. The study of large structures is not possible because of the limited capacity of computer systems. So in this study the addition of monomer units to the initial monomer were continued until pentamer because the NQR parameters approach a steady limit (see Tables 1-4). Calculations of the chlorine and nitrogen nuclear magnetic shielding and EFG tensors were based on these models and by using four functionals, B3LYP, M06-2X, M06L, CAM-B3LYP, and 6-311++G(d,p) basis set. The M06-2X/6-311++G(d,p) method was used for calculating NBO parameters. 3. Results and Discussion 3. 1. Investigation of NQR Parameters The models for amino acid hydrochloride salts, shown in Figures 1 and 2, were utilized in quantum chemical calculations of the NMR interaction tensors. Results presented in Tables 1-4 show that molecular interactions significantly affect the electric field and its gradient in these two hydrochloride clusters, and also indicate that the quadrupolar coupling constant of chlorine and nitrogen nuclei decrease from dimmer to pentamer in all functionals. Reduction in the Cq value is connotative of an increment in hydrogen bond strength.40 According to Tables 2 and 4, a decrease in CQ in alanine hydrochloride salt is more significant than a decrease in CQ in another salt, which could be as a result of hydrogen bond forma- Table 1. Calculated chlorine-35 quadrupolar and chemical shift data for various Alanine hydrochloride clusters. Model Functional °iso (ppm) An (ppm) |Cq| (MHz) N Monomer B3LYP 999.78 187.45 15.96 0.03 M062X 1018.51 172.77 15.51 0.04 M06L 1001.26 162.32 14.28 0.05 CAM-B3LYP 1014.52 172.63 15.07 0.03 Dimer B3LYP 1018.05 157.55 12.25 0.59 M062X 1034.18 146.70 11.81 0.62 M06L 1014.35 142.25 10.91 0.62 CAM-B3LYP 1030.95 146.77 11.56 0.59 Trimer B3LYP 947.37 116.17 7.41 0.68 M062X 958.53 115.58 6.58 0.73 M06L 958.17 103.99 6.83 0.72 CAM-B3LYP 962.42 112.32 6.94 0.69 Tetramer B3LYP 946.32 117.85 7.22 0.72 M062X 956.99 119.30 6.60 0.77 M06L 951.17 104.22 6.72 0.75 CAM-B3LYP 961.27 113.87 6.77 0.72 Pentamer B3LYP 946.90 116.80 7.20 0.73 M062X 958.96 117.62 6.66 0.79 M06L 943.15 112.42 6.73 0.75 CAM-B3LYP 961.62 113.35 6.76 0.73 Exp. (35Cl) (913.4 ± 5 - 6.4 ± 0.1 -0.75 ± 0.06 Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid 244 Acta Chim. Slov. 2016, 63, 241-250 tion. In an alanine hydrochloride salt, the nitrogen atom can contribute to hydrogen bonding with a chlorine atom of a neighboring molecule, but it is not possible for a nitrogen atom in the threonine hydrochloride salt, and it contributes to one hydrogen bond. So, we expected that all changes in NQR parameters were larger in an alanine hydrochloride salt. The asymmetry parameter (^q) can show the information about the symmetry of the nuclear environment. The asymmetry parameter of chlorine in both hydrochloride salts increases regularly, but for nitrogen atoms this parameter decreases from dimmer to pen-tamer. All changes were investigated from dimmer to pentamer, because the molecule is still in a gas phase rather than a crystalline state in a monomer situation. Consequently, we can use NMR and NQR parameters to evaluate any changes in the structure of amino Table 2. Calculated nitrogen quadrupolar and chemical shift data for various Alanine hydrochloride clusters. Model Functional Oiso (ppm) Ao (ppm) |Cq| (MHz) ho) Monomer B3LYP 187.53 13.79 1.73 0.30 M062X 194.10 12.87 1.70 0.29 M06L 196.38 10.45 1.64 0.25 CAM-B3LYP 193.13 12.97 1.73 0.31 Dimer B3LYP 187.13 12.35 1.60 0.96 M062X 193.74 13.74 1.56 0.96 M06L 196.47 8.56 1.51 0.94 CAM-B3LYP 192.64 12.51 1.60 0.97 Trimer B3LYP 189.69 9.54 1.45 0.95 M062X 195.98 11.08 1.41 0.95 M06L 198.00 6.5 1.49 0.87 CAM-B3LYP 195.01 9.86 1.46 0.94 Tetramer B3LYP 189.89 9.53 1.44 0.93 M062X 196.37 10.23 1.40 0.93 M06L 198.86 4.89 1.48 0.85 CAM-B3LYP 195.20 9.85 1.45 0.92 Pentamer B3LYP 189.88 9.32 1.44 0.93 M062X 197.00 9.43 1.40 0.93 M06L 199.54 4.50 1.48 0.85 CAM-B3LYP 195.21 9.65 1.45 0.91 Table 3. Calculated chlorine-35 quadrupolar and chemical shift data for various threonine hydrochloride clusters. Model Functional Oiso (PPm) Ao (ppm) |Cq| (MHz) hol Monomer B3LYP 1052.65 145.73 9.79 0.22 M062X 1084.44 112.74 8.68 0.20 M06L 1028.77 144.64 8.77 0.21 CAM-B3LYP 1078.63 113.24 8.66 0.22 Dimer B3LYP 1044.78 121.91 8.15 0.33 M062X 1070.92 100.25 7.22 0.33 M06L 1030.05 117.61 7.37 0.31 CAM-B3LYP 1066.07 98.69 7.22 0.34 Trimer B3LYP 1048.63 111.08 7.43 0.35 M062X 1071.60 96.06 6.58 0.34 M06L 1034.63 112.99 6.73 0.32 CAM-B3LYP 1068.10 92.15 6.61 0.35 Tetramer B3LYP 1048.74 108.96 7.31 0.35 M062X 1071.27 95.40 6.47 0.35 M06L 1033.93 115.59 6.62 0.33 CAM-B3LYP 1068.29 90.76 6.51 0.35 Pentamer B3LYP 1048.87 107.42 7.26 0.36 M062X 1072.88 88.82 6.37 0.36 M06L 1040.94 114.29 6.01 0.33 CAM-B3LYP 1068.40 89.84 6.44 0.36 Exp. (35Cl) (920.37 ± 10 - 5.4 ± 0.1 0.94 ± 0.02 Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid Acta Chim. Slov. 2016, 63, 241-250 245 Table 4. Calculated nitrogen quadrupolar and chemical shift data for various threonine hydrochloride clusters. Model Functional 0iso (ppm) Ao (ppm) |Cq| (MHz) IHq| Monomer B3LYP 199.57 36.73 1.07 0.69 M062X 205.94 32.31 1.03 0.68 M06L 205.93 33.56 1.01 0.75 CAM-B3LYP 204.35 35.15 1.08 0.67 Dimer B3LYP 200.67 34.46 1.00 0.66 M062X 207.47 28.40 0.96 0.65 M06L 205.56 31.11 0.94 0.72 CAM-B3LYP 205.49 32.86 1.01 0.64 Trimer B3LYP 201.00 32.72 0.94 0.61 M062X 207.81 26.64 0.90 0.60 M06L 206.26 30.39 0.88 0.68 CAM-B3LYP 205.98 31.19 0.95 0.59 Tetramer B3LYP 200.95 32.50 0.93 0.60 M062X 207.75 26.43 0.89 0.59 M06L 206.39 28.96 0.87 0.67 CAM-B3LYP 205.96 31.07 0.94 0.58 Pentamer B3LYP 200.93 32.30 0.93 0.60 M062X 207.96 25.98 0.89 0.58 M06L 206.32 28.60 0.86 0.66 CAM-B3LYP 205.99 30.88 0.94 0.58 acids, hence, we can determine any changes in the structure of ion channels. 3. 2. Computational Errors Usually the magnitude of Cq ( Cl) measured from NMR spectra of chloride ions in organic and inorganic salts range from essentially zero in cubic salts to greater than 9.0 MHz,41'42 and the results of the calculations of the chlorine-35 quadrupolar coupling constants measured in this study were in this range. According to available experimental data for chlorine nucleus,25,43 we can compare four methods used for calculating NQR parameters in these two amino acids. By comparing the experimental and Figure 3. Comparison of computational methods used in calculation 35Cl CQ of both hydrochloride salts. Moridi et al.: DFTStudies of NH-Cl Hydrogen Bond of Amino Acid ... 246 Acta Chim. Slov. 2016, 63, 241-250 calculated values shown in Tables 1 and 3, the M06L/6-311++G(d,p) method is more accurate and has the lowest computational error for calculating CQ in these molecules. Figure 3 shows the average of errors calculated for two hydrochloride salts. According to available NMR experimental data for chlorine nuclei,43 percent errors in calculating oiso of the chlorine nucleus in alanine hydrochloride salt for B3LYP, M06-2X, M06L, CAM-B3LYP functional were 3.10%, 3.23%, 2.69%, and 4.71%, respectively, and for threonine hydrochloride were 12.74%, 15.32%, 11.82%, and 14.84%, respectively. So, we can see again that the M06L/6- 311++G(d,p) method was the most accurate method in these two amino acids. 3. 3. Correlation Between NMR and NBO Parameters Changes in anisotropy parameter are correlated to the NBO parameters. Chemical shielding anisotropy of ni- Figure 4. Correlation between percent of P orbital and Ac in alanine hydrochloride salt. Figure 5. Correlation between percent of P orbital and Ac in threonine hydrochloride salt. Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid Acta Chim. Slov. 2016, 63, 241-250 247 Table 5. NBO analysis of NH(1)-Cl interaction for alanine hydrochloride clusters calculated with M06-2X/6-311++G(d,p) method. Model Enbo (kCal/mol) nCl °N-H % S Character % Polarization % P 1 52.58 sp012 0.4445 sp292-0.8958 s 25.48 74.49 74.49 2 43.47 sp014 0.4552 sp312-0.8904 s 24.24 75.72 75.72 3 35.32 sp038 0.4684 sp3.10-0.8835 s 24.36 75.60 75.60 4 33.64 sp038 0.4704 sp310-0.8824 s 24.38 75.59 75.59 5 32.84 sp038 0.4712 sp310-0.8820 s 24.37 75.58 75.58 Table 6. NBO analysis of NH-Cl interaction for threonine hydrochloride clusters calculated with M06-2X/6-311++G(d,p) method. Model Enbo (kCal/mol) nCl °N-H % S Character % Polarization % P 1 50.32 sp011 0.4646 sp294-0.8998 s 25.31 80.96 74.66 2 40.87 sp0.14 0.4753 sp314-0.8934 s 24.07 79.82 75.89 3 32.63 sp0.40 0.4885 sp3.12-0.8875 s 24.19 78.77 75.77 4 31.83 sp0.41 0.4905 sp311-0.8864 s 24.21 78.57 75.75 5 31.52 sp0.41 0.4913 sp311-0.8860 s 24.22 78.50 75.74 trogen atom in alanine hydrochloride decreases with increasing cluster size. According to Table 5, hybridization of nitrogen atom changes from SP312 to SP310, this increase in s character and decrease in p character cause the electronic cloud around the nucleus to become more symmetric, and chemical shielding anisotropy subsequently decreases. Similarly, a nitrogen atom in threonine hydrochloride changes from SP314 to SP311, so the symmetry around the nucleus increases, and the anisotropy parameter decreases, as shown in Tables 4 and 6, and Figures 4 and 5. 3. 4. Analysis of Structural Parameters In this study we have investigated NH-Cl hydrogen bond in crystal lattice. Two effects influence the A-H-B hydrogen bond: the hyperconjugative effect that decreases the strength of A-H bond and subsequently increases the length of the A-H bond, and the rehybridization effect that leads to an increase in the A-H bond strength that then decreases the A-H bond length.44 The hyperconju-gative effect is connected with the energy of electron charge transfer, ENBO, and will increase if this energy in- Figure 6. correlation between s-character and N-H bond length for N-H-Cl interaction in alanine hydrochloride salt. Moridi et al.: DFTStudies of NH-Cl Hydrogen Bond of Amino Acid ... 248 Acta Chim. Slov. 2016, 63, 241-250 Figure 7. correlation between s-character and N-H bond length for N-H—Cl interaction in threonine hydrochloride salt. Table 7. Structural parameters for Alanine hydrochloride clusters optimized with M06-2X/6-31++G(d,p) method. Model rN-H (A rH-Cl (A) 1 1.123 2.075 2 1.098 2.101 3 1.073 2.127 4 1.070 2.131 5 1.069 2.132 nine hydrochloride, as evident from Table 8, the NH bond length decreases from 1.059 A to 1.033 A. The rehybridi-zation effect simultaneously increases, as shown in Table 6, due to reduction in ENBO and increase in s-character. These correlations have been represented in Figures 6 and 7. 4. Conclusions Table 8. Structural parameters for Threonine hydrochloride clusters optimized with M06-2X/6-31++G(d,p) method. Model rN-H (A rH-Cl (A) 1 1.085 2.109 2 1.059 2.135 3 1.044 2.161 4 1.039 2.165 5 1.033 2.167 creases. The s-character of the A-atom hybrid orbital in the A-H bond is directly dependent to the rehybridization process. The structural parameters for alanine hydrochlo-ride are presented in Table 7. According to Table 5, s-cha-racter from dimer to pentamer increases from 24.24 to 24.37, but Enbo decreases from 43.47 to 35.32 kcal/mol. Therefore, in this interaction, we expect that NH bond length decreases from dimer to pentamer, the accuracy of which can be inferred from Table 7. Similarly, for threo- The EFG and the chemical shielding tensors have been calculated for chlorine and nitrogen nuclei, via the following four functionals: B3LYP, M062X, M06L, and CAMB3LYP and with 6-311++G(d,p) basis set. The aim of this study was to demonstrate the sensitivity of NMR interaction tensors to slight differences in the local environment at every nucleus where there was a NH-Cl hydrogen bond. This matter is so crucial because it illustrates the changes in ion channel structure, whereby the NMR and NQR parameters are significantly changed when the structures of the monomer transform to penta-mer. The results agree with experimental data, which illustrates that the M06L/6-311++G(d,p) method is the most accurate method for NMR and NQR calculations in these two amino acids. In addition, it is shown that there was a high correlation between NMR parameters and NBO parameters, and between structural parameters and NBO parameters. Information from NMR, NQR, and NBO analysis are useful for interpretation of the structure in both solu- Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid Acta Chim. Slov. 2016, 63, 241-250 249 tion and solid states. These techniques are especially useful for biological molecules such as proteins and also for larger systems with unknown structure. 5. References 1. J. S. Murray, M. C. Concha, P. Lane, P. Hobza, P. Politzer, Blue shifts vs red shifts in o-hole bonding, J. Mol. Model., 2008, 14, 699-704. http://dx.doi.org/10.1007/s00894-008-0307-y 2. S. Scheiner, Hydrogen bonding: a theoretical perspective, Oxford University Press, New York, 1997. 3. M. Esrafili, H. Behzadi, NL. Hadipour, Density functional theory study of N-H-O, O-H-O and C-H-O hydrogenbon-ding effects on the 14N and 2H nuclear quadrupole coupling tensors of N-acetyl-valine, Biophys. Chem., 2008, 133, 11-18. http://dx.doi.org/10.1016Zj.bpc.2007.11.006 4. H. Behzadi, MD. Esrafili, NL. Hadipour, A theoretical study of 17O, 14N and 2H nuclear quadrupole coupling tensors in the real crystalline structure of acetaminophen, Chem. Phys., 2007, 333, 97-104. http://dx.doi.org/10.1016/j.chemphys.2007.01.011 5. S. J. Grabowski, W. A. Sokalski, E. Dyguda, J. Leszczynki, Quantitative classification of covalent and noncovalent H-bonds, Phys. Chem. B, 2006, 110, 6444-6446. http://dx.doi.org/10.1021/jp0600817 6. M. D. Esrafili, A theoretical investigation of the characteristics of hydrogen/ halogen bonding interactions in dibromo-nitroaniline, J. Mol. Model., 2012, 19, 1417-1427. http://dx.doi.org/10.1007/s00894-012-1691-x 7. R. H. Holm and E. I. Solomon, Chem. Rev., 1996, 96, 22372238 (thematic issue). http://dx.doi.org/10.1021/cr9500390 8. C. Ceccarelli, G. A. Jeffrey, R. Taylor, A survey of O-H-O hydrogen bond geometries determined by neutron diffraction, J. Mol. Struct., 1981, 70, 255-271. http://dx.doi.org/10.1016/0022-2860(81)80112-3 9. G. A. Jeffrey, W. Saenger, Hydrogen Bonding in Biological Structures, Springer-Verlag, Berlin, 1991. http://dx.doi.org/10.1007/978-3-642-85135-3 10. T. Steiner, W. Saenger, Geometry of C-H-O hydrogen bonds in carbohydrate crystal structures, Analysis of neutron diffraction data, J. Am. Chem. Soc., 1992, 114, 10146-10154. http://dx.doi.org/10.1021/ja00052a009 11. T. Steiner, W. Saenger, Role of C-H-O hydrogen bonds in the coordination of water molecules, Analysis of neutron diffraction data, J. Am. Chem. Soc., 1993,115, 4540-4547. http://dx.doi.org/10.1021/ja00064a016 12. D. Braga, R. Grepioni, K. Biradha, V. R. Pedireddi, G. R. Desiraju, Hydrogen bonding in organometallic crystals, 2. C-H-O hydrogen bonds in bridged and terminal first-row metal carbonyls, J. Am. Chem. Soc., 1995, 117, 3156-3166. http://dx.doi.org/10.1021/ja00116a020 13. W. B. Guggino, Ion Chloride Channels: Current Topics in Membranes, A. Kleinzeller, D.M. Fambrough, Eds., Academic Press, San Diego, 1994, 42. 14. F. M. Ashcroft, Ion Channels and Disease, Academic Press, San Diego, 2000. 15. M. E. Loewen, G. W. Forsyth, Structure and Function of CLCA Proteins, Physiol. Rev., 2005, 85, 1061-1092. http://dx.doi.org/10.1152/physrev.00016.2004 16. T. J. Jentsch, T. Maritzen, A. A. Zdebik, Chloride channel diseases resulting from impaired transepithelial transport or vesicular function, J. Clin. InVest., 2005, 115, 2039- 2046. http://dx.doi.org/10.1172/JCI25470 17. R. Dutzler, E. B. Campbell, R. MacKinnon, Gating the Selectivity Filter in ClC Chloride Channels, Science, 2003, 300, 108- 112. http://dx.doi.org/10.1126/science.1082708 18. S. B. Long, E. B. Campbell, R. MacKinnon, Crystal Structure of a Mammalian Voltage-Dependent Shaker Family K+ Channel, Science, 2005, 309, 897- 903. http://dx.doi.org/10.1126/science.1116269 19. E. A. C. Lucken, Nuclear Quadrupole Coupling Constants, Academic Press, London, 1969. 20. A. Bax, Weak alignment offers new NMR opportunities to study protein structure and dynamics, Protein Sci., 2003, 12, 1-16. http://dx.doi.org/10.1110/ps.0233303 21. P. M. Hwang, L. E. Kay, Solution structure and dynamics of integral membrane proteins by NMR: A case study involving the enzyme PagP, Methods Enzymol., Part C, 2005, 394, 335-350. http://dx.doi.org/10.1016/s0076-6879(05)94013-5 22. S. G. Zech, A. J. Wand, A. E. McDermott, Protein structure determination by high-resolution solid-state NMR spectros-copy: Application to microcrystalline ubiquitin, J. Am. Chem. Soc., 2005, 127, 8618-8626. http://dx.doi.org/10.1021/ja0503128 23. C. P. Jaroniec, C. E. MacPhee, V. S. Bajaj, M. T. McMahon, C. M. Dobson, R. G. Griffin, High-resolution molecular structure of a peptide in an amyloid fibril determined by magic angle spinning nmr spectroscopy, Proc. Natl. Acad. Sci. U.S.A., 2004, 101, 711-716. http://dx.doi.org/10.1073/pnas.0304849101 24. D. L. Bryce, M. Gee, R. E. Wasylishen, High-field chlorine NMR spectroscopy of solid organic hydrochloride salts: A sensitive probe of hydrogen bonding environment, J. Phys. Chem. A, 2001, 105, 10413-10421. http://dx.doi.org/10.1021/jp011962a 25. R. P. Chapman, D. L. Bryce, A high-field solid-state 35/37Cl NMR and quantum chemical investigation of the chlorine quadrupolar and chemical shift tensors in amino acid hydrochlorides, Phys. Chem. Chem. Phys., 2007, 9, 62196230. http://dx.doi.org/10.1039/b712688c 26. J. R. Yates, C. J. Pickard, F. Mauri, Calculation of NMR chemical shifts for extended systems using ultrasoft pseudopotentials, Phys. Rev. B., 2007, 76. http://dx.doi.org/10.1103/physrevb.76.024401 27. P. Chananont, T. A. Hamor, stereochemistry of anticholinergic agents. XV. Structure of 2-(diethylamino)ethyl 1-cyclo-hexylcyclohexanecarboxylate hydrochloride (dicyclomine hydrochloride), Acta Crystallogr., Sect. B: Struct. Sci., 1981, 37, 1878-1881. Moridi et al.: DFTStudies of NH-Cl Hydrogen Bond of Amino Acid ... 250 Acta Chim. Slov. 2016, 63, 241-250 http://dx.doi.org/10.1107/S0567740881007462 28. R. Kingsfordadaboh, E. Hayashi, M. Haisa, S. Kashino, Crystal-structures and molecular-conformations of isoprenaline hydrochloride and (s)-isoprenaline hydrogen (2R,3R)-tartra-te, Bull. Chem. Soc. Jpn., 1993, 66, 2883-2888. http://dx.doi.org/10.1246/bcsj.66.2883 29. J. N. Latosinska, A correlation of spectroscopic parameters from different magnetic resonance spectroscopies for thiazides: a study by NQR, NMR, EPR and DFT methods, Chem. Phys. Lett., 2004, 398, 324-329. http://dx.doi.org/10.1016Zj.cplett.2004.09.088 30. Remya Karunakaran, H. Suresh Cherumuttathu, Which density functional is close to CCSD accuracy to describe geometry and intraction energy of small noncovalent dimmers? A benchmark study using Gaussian09, Comp. Chem., 2013, 34, 1341-1353. http://dx.doi.org/10.1002/jcc.23263 31. Y. Zhao, D. G. Truhlar, The M06 suite of density functionals for main group thermochemistry, kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06 functionals and twelve other functionals, Theor. Chem. Acc., 2008, 120, 215-241. http://dx.doi.org/10.1007/s00214-007-0310-x 32. Y. Zhao, D. G. Truhlar, A new local density functional for main-group thermochemistry, transition metal bonding, ther-mochemical kinetics, and noncovalent interactions, J. Chem. Phys., 2006, 125, 194101. http://dx.doi.org/10.1063/L2370993 33. U. Haeberlen, Advances in Magnetic Resonance, Supplement 1, Academic Press, New York, 1976. 34. H. W. Spiess, Rotation of molecules and nuclear spin relaxation, in: P. Diehl, E. Fluck, Kosfeld, (Eds.), NMR Basic Principles and Progress, Springer- Velag, Berlin, 1978, 15, 55-214. http://dx.doi.org/10.1007/978-3-642-66961-3_2 35. J. Slawomir, Grabowski, Hydrogen and halogen bonds are ruled by the same mechanisms, Phys.Chem. Chem. Phys., 2013, 15, 7249. http://dx.doi.org/10.1039/c3cp50537e 36. S. J. Grabowski, What is the covalency of hydrogen bonding?, Chem.Rev., 2011, 111, 2597-2625. http://dx.doi.org/10.1021/cr800346f 37. H. A. Bent, An appraisal of valence-bond structures and hybridization in compounds of the first-row elements, Chem.Rev., 1961, 61, 275-311. http://dx.doi.org/10.1021/cr60211a005 38. M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S. Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. J. Su, T. L. Windus, M. Dupuis, J. A. Montgomery, General Atomic and Molecular Electronic Structure System, J. Comput. Chem., 1993, 14, 1347- 1363. http://dx.doi.org/10.1002/jcc.540141112 39. B. Di Blasio, V. Pavone and C. Pedone, Cryst. Struct. Commun., 1977, 6, 745-748. 40. Kazuo Yamauchi, Shigeki Kuroki, Isao Ando, Takuo Ozaki, Akira Shoji, 17O NMR chemical shifts and quadrupole coupling constants in solid poly(L-alanine)s determined using a high-speed MAS technique, Chem. Phys. Let., 1999, 331336. 41. T. O. Sandland, L. S. Du, J. F. Stebbins and J. D. Webster, Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study, Geochim. Cosmochim. Acta, 2004, 68, 5059-5069. http://dx.doi.org/10.1016/j.gca.2004.07.017 42. S. Hayashi and K. Hayamizu, Accurate determination of NMR chemical shifts in alkali halides and their correlation with structural factors, Bull. Chem. Soc. Jpn., 1990, 63, 913919. http://dx.doi.org/10.1246/bcsj.63.913 43. Christel Gervais, Ray Dupree, Kevin J. Pike, Christian Bonhomme, Mickaell Profeta, Chris J. Pickard, Francesco Mauri, Combined first-principles computational and experimental multinuclear solid-state NMR investigation of amino acids, J. Phys. Chem. A, 2005, 109, 6960-6969. http://dx.doi.org/10.1021/jp0513925 44. I. V. Alabugin, M. Manoharan, S. Peabody and F. Weinhold, Electronic basis of improper hydrogen bonding: a subtle balance of hyperconjugation and rehybridization, J. Am. Chem. Soc., 2003, 125, 5973-5987. http://dx.doi.org/10.1021/ja034656e Povzetek S kvantno mehanskimi izračuni smo proučevali NH-Cl vodikove vezi hidrokloridnih soli dveh amino kislin, alanina in treonina. S pomočjo štirih funkcionalov, B3LYP, M062X, M06L, CAM-B3LYP in z uporabo 6-311++G(d,p) baznega seta smo izračunali resonančne parametre za nuklearno magnetno resonance in nuklearno kvadropolno resonanco. Z M062X/6-31++G(d,p) metodo in analizo veznih orbital z uporabo M062X/6-311++G(d,p) nivoja smo izvedli geometrijsko optimizacijo. Resonančni parametri kažejo možne strukture od monomer do pentamer, povezo med njimi in parametri veznih orbital pa smo uporabili za študij možne tvorbe kristalov. Moridi et al.: DFT Studies of NH-Cl Hydrogen Bond of Amino Acid DOI: I0.i7344/acsi.20i5.i992_Acta Chim. Slov. 2016, 63, 251-257_ 251 Scientific paper Catalytic Alkylation of Acetone with Ethanol Over Pd/carbon Catalysts in Flow-through System Via Borrowing Hydrogen Route X _ Gyula Novodarszki, Gyorgy Onyestyak,* Agnes Farkas Wellisch and Aranka Pilbath Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1519 Budapest, P.O. Box 286., Hungary * Corresponding author: E-mail: onyestyak.gyorgy@ttk.mta.hu, tel.: +36-1-382-6844 Received: 15-09-2015 Abstract Consecutive alkylation of acetone with ethanol as model reactants was studied in order to obtain biomass based fuels by continuous processing of acetone-butanol-ethanol (ABE) mixture. Butanol, which can inevitably form as Guerbet side product in a self-aldol reaction of ethanol was not applied in our study as an initial component, in order to follow the complexity of the reaction mechanism. A flow-through reactor was applied with inert He or reducing H2 stream in the temperature range of 150-350 °C. Efficient catalysts containing Pd and base (K3PO4 or CsOH) crystallites were prepared applying commercial activated carbon (AC) support. The catalyst beds were pre-treated in H2 flow at 350 °C. Mono- or dialkylated ketones were formed with high yields and these products could be reduced only to alcohols over palladium. Keywords: Acetone; Alcohols; C-alkylation; Pd/C catalysts 1. Introduction A major 21st century goal is the economical utilization of biomass resources for production of fuels and chemicals. The technologies on various biomass platforms involve combinations of mechanical, thermal, chemical, and biochemical processes including separation operations.1-3 Instead of the less advantageous thermochemical routes, favorable microbiological destruction process - e.g. Mix-Alco - can be applied4 to produce volatile fatty acids, mainly acetic acid.5-6 The overall chemical reaction without loss of biomass conducted by species of anaerobic bacteria, including members of the genus Clostridium may be represented as: C6H12O6 ^ 3 CH3COOH (1) The selective deoxygenation of carboxylic acids to alcohols seems to be successfully solved recently using indium co-catalyst with nickel or platinum host metal.7 Nowadays the Clostridium species attracted again interest and are accepted for their ability to produce aceto- ne, n-butanol and ethanol in a 2.3:3.7:1.0 molar ratio from sugars, carbohydrates, lignocelluloses, etc. for use as renewable alternative transportation fuels. Although co-production of acetone lowers the yield of alcohol biofuels, but the lower oxygen content of ABE mixture is advantageous compared to carboxylic acids. A recent study was aimed to develop an improved Clostridium acetobutylicum strain with enhanced alcohol production capability, but complete conversion of acetone into isopropanol are further challenges.8 Catalytic dehydration of the ABE mixtures was studied in order to deoxygenate it, but the resulted products were mostly un-saturated hydrocarbons.9 The obtained mixture was similarly disadvantageous as the products of thermochemical method. Anbarasan and co-workers10 proposed a chemical route to convert fermentation ABE product into hydrocarbons that can be used for fuel. Nucleophilic a-carbons of acetone can form C-C bond with electrophilic alcohols produced in ABE fermentation, resulting in longer chain length hydrocarbons than the original fermentation products. Thus, the paired functionalities (nucleophilic a-car-bons of the acetone and electrophilic a-carbon of the alco- Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over 252 Acta Chim. Slov. 2016, 63, 251-257 hols) enable to construct higher alkanes from two-carbon, three carbon and four-carbon precursors. The alkylation under suitable conditions (110 oC in toluene using stirred pressurized batch reactor) results in C5-C11 or longer-chain ketones,11 which may be deoxygenated to paraffin, the components of fuel. Palladium on carbon was superior to the other metals (Ir, Ru, Rh, Pt, Ni) using in various forms with different bases in molar equivalent to alcohols. K3PO4 base additive seemed to be the most efficient. The applied metals are working based on hydrogen borrowing methodology.11-13 Further the applied bases type and amount is a determining factor in the process. G. Xu and co-workers14 - mimicking ABE fermentation product - demonstrated direct a-alkylation of ketones with alcohols in water (instead of toluene10) over Pd/C catalytic system in autoclave. Equivalents of different bases (K3PO4, LiOH, NaOH or KOH) to the amount of ketone were also used. Q. Xu and co-workers15 conceive that transition-metal-catalyzed a-alkylation of ketones with alcohols still have drawbacks, consequently they prefer the "catalyst-free" dehydrative a-alkylation. However, high amount of bases (NaOH or KOH) are still applied in the studied alkylation reactions. The literature shows as yet only studies in small reaction tubes which have several disadvantages and are applicable only as quick catalyst tests. Processing of ABE mixture - which can be one way of biomass utilization in high volume - needs a continuous procedure. For this purpose move from batch to flow-through system was aimed for a detailed study. The present study relates to the application of the carbon supported catalysts in fixed beds working in vapor phase a-alkylation using acetone and ethanol, as model reactants instead of ABE mixture. Butanol as reac-tant can form as Guerbet side product in a self-aldol reaction of ethanol, consequently it was not feed in the reactor in order to follow and understand the reaction mechanism. 2. Experimental Cited references did not give detailed information about the usually used "5% palladium on carbon" catalysts. In this study, a commercial pelletized activated carbon (AC) /cylinders with 0.8 mm diameter and 2-4 mm length/ (Norit ROX 0.8 EXTRA, specific area: 1150 m2/g) as inert support was applied. The AC first was dried at 110 °C, then impregnated with CsOH (Fluka AG) or K3PO4 (Aldrich) solutions using incipient wetness method and dried again at 110 °C. For 1 g support 0.2 g bases were added resulting in plus 20 m% loadings. Finally 5 m% palladium is also loaded using tetraamine-palla-dium(II)nitrate solution (STREM Chemicals). Nitrogen physisorption measurements were carried out at -196°C using Thermo Scientific Surfer static volumetric adsorption analyzer. Before the adsorption analysis samples were outgassed for 3 h at 200 °C. The catalytic alkylation of acetone (A) (99.5 %, Reanal) with ethanol (E) (99.7 %, Reanal) mixed in 1:2 molar ratio was studied in a high-pressure fixed bed flow-through reactor16 at 21 bar total pressure in the temperature range of 150-350 °C using inert helium or reducing hydrogen streams. Weight of catalyst bed (1.2-4.6 g) and flow rate of liquid mixture (1.2-4.6 gAE/h) were varied controlling WHSV values between 1-4. In general the catalysts were pretreated in situ in hydrogen flow in the reactor at 350 °C and 21 bar for 1 h in order to obtain active metallic surface. The reaction was allowed to run one hour at each condition to attain steady state. The effluent during the second hour was collected, depressurized and cooled to room temperature. The liquid product mixture at ambient conditions was analyzed by gas chromatograph using a GC-MS (Shimadzu QP2010 SE,) capable to identify products formed in low concentration, equipped with a ZB-WAX plus capillary column. The gaseous reactor effluent was analyzed for detection of CO2, CO, CH4 and light hydrocarbons using an on-line gas chromatograph (HP 5890) with thermal conductivity detector (TCD) on Carboxen 1006 PLOT capillary column. The conversion of the two component reaction mixture cannot be well defined, due to the complex reaction network shown later. Both of the reactants are transformed to such a kind of by-products (isopropyl alcohol, ace-taldehyde and butanol), which can take part further in the main alkylation reaction network. Thus, the main alkyla-ted products (ketones and alcohols) with the actual yields given by the calculation method below are used for characterizing the activity and selectivity of the applied catalysts: yield (wt%) = flow of a productout (g/h) / flow of the reaction mixture^ (g/h) x 100 3. Results and Discussion AC support is well applicable in fixed bed flow-through reactors being inert in the studied reaction system. In Fig. 1 isotherms of nitrogen adsorption related to carbon content characterize the porosity of the support and the prepared catalysts. Shape of isotherms reflects highly microporous materials with high specific surface area (>1000 m2/g) which is characteristic for activated carbons containing less slitlike pores than 1 nm between carbon sheets. Presence of hysteresis loop indicates mesopores (mean pore diameter (BJH) is approx. 4 nm) of low diffusional resistance created in the course of pellet formation process. In the cited batch reactor experiments10,14-15 high amounts of bases, some equivalents related to one of the reactants were used in the reaction mixtures. Such high base/reactant ratio is also given in our experiments over fixed catalyst beds. Presence of impregnated bases on AC only hardly decrease the adsorbed amount of nitrogen re- Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over Acta Chim. Slov. 2016, 63, 251-257 253 lated to AC content (Fig. 1) which means that base and palladium metal can form in the mesopores larger crystals than the entrance of micropores. However, the mesopo-rous volumes, area of hysteresis loops significantly decreased. Active components are on the surface, including surface of larger pores, consequently the catalytic reaction take place in the mesopores, too. Table 1 and 2 designed in identical structure demonstrate differences in formation of main products using inert (helium) or reactive (hydrogen) carrier gases, respectively. In helium the mono-alkylated- (2-pentanone, 2-heptanone) and the bi-alkylated-ketones (4-heptanone, 4-nonanone) are the main products formed with desired good selectivity. Without palladium loading only low catalyst activities were observed. The "catalyst-free" dehydrative a-alkyla-tion15 cannot be suggested in flow-through system. To picture the conversion of mixture (acetone +etha-nol) in Table 1 and 2 sum of main products (with exception of isopropyl alcohol) are shown which values ap- Catalyst 5Pd,20K3PO4/AC 5Pd,20CsOH/AC Reac. temp. °C 200 250 300 350 200 250 300 350 isopropyl alc. - 0.9 2.0 2.2 0.6 1.0 1.5 1.8 butanol - - - - - - - - 2-pentanone 0.7 18.3 24.9 34.7 12.6 19.4 24.1 29.6 2-pentanol - - - - - - - - 4-heptanone 0.8 4.6 14.3 21.6 2.9 7.5 13.8 20.0 2-heptanone - 1.1 1.7 2.1 0.3 2.0 3.1 4.3 4-heptanol - - - - - - - - 4-nonanone 0.2 0.6 1.8 7.8 0.4 2.2 5.7 6.5 CO - 0.8 4.1 9.0 - 0.9 3.7 7.0 CH4 - 1.7 5.1 7.9 - 0.5 2.2 5.5 CO2 - - 4.1 5.3 - - 1.1 4.4 Sum 1.7 27.1 56.0 88.4 32.5 53.7 77.3 (WHSV = 1 gAE h 1 gcat 1; p = 21 bar; A/E = 1:2 mol/mol) Other products with low yield: acetaldehyde; ethyl acetate; methyl isobutyl ketone; buta-noic acid ethyl ester; 4-decanone; 4-undecanone; 6-undecanone; 4-heptanone, 3-ethyl, 2-methyl; 2-pentanone, 3-ethyl; 2-heptanone, 4-methyl; etc. Table 2. Yields (wt%) of main products obtained in hydrogen stream. Catalyst 5Pd,20K3PO4/AC 5Pd,20CsOH/AC Reac. temp. °C 200 250 300 350 200 250 300 350 isopropyl alc. 23.6 19.9 15.0 9.1 22.5 18.4 12.4 5.8 butanol 0.3 1.0 3.1 1.2 - 1.3 4.2 - 2-pentanone 1.5 3.6 10.6 19.5 3.1 3.8 8.8 15.8 2-pentanol 7.5 11.3 9.4 5.5 13.5 17.1 4.2 3.1 4-heptanone - - 7.6 18.4 - - 13.8 23.0 2-heptanone - - 0.5 2.0 - - 0.5 1.0 4-heptanol 0.2 2.7 2.7 2.7 0.3 6.5 6.9 5.3 4-nonanone - - 1.1 3.6 - 1.1 2.2 5.2 CO - 0.2 1.8 6.7 - - 2.6 4.3 CH4 - 0.6 2.6 5.6 - - 1.7 3.6 co2 - - 2.8 2.3 - - 0.8 1.9 Sum 9.5 19.4 42.2 67.5 16.9 29.8 45.7 63.2 (WHSV = 1 gAE h 1 gcat 1; p = 21 bar; A/E = 1:2 mol/mol) Other products with low yield: heptane; nonane; etc. Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over ... (D i g 1901 u-r-■-1->-1-■-1->-1-■- 0.0 0-2 0.4 0.6 0.6 1.0 Relative pressure, pip 0 Figure 1. Adsorption isotherms of nitrogen obtained at -196 °C on the parent AC (■ - adsorption, □ - desorption) and the CsOH loaded (• - adsorption, O - desorption) samples. Only the parent and the CsOH loaded samples are shown in figure, because all impregnated samples give nearly the same isotherms. Table 1. Yields (wt%) of main products obtained in helium stream. 254 Acta Chim. Slov. 2016, 63, 251-257 Scheme 1. Schematic diagram of reactions involved in the conversion of acetone and ethanol on the base of detected main products. Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over Acta Chim. Slov. 2016, 63, 251-257 255 proach the conversion of the fed mass flow. The significant production of 2-heptanone and 4-nonanone is interesting which testify that butanol can form as a Gourbet byproduct, although it cannot be directly detected using helium. Consequently numerous variations of potential ketones can be detected in very different concentration alike as real ABE mixture has been studied. Alcohols did not appear when applying helium -those were significantly formed only in hydrogen. Over Pd catalysts ketones can be reduced to alcohols; paraffin preferable for fuels are detected only under severe reaction conditions, at high temperature where numerous useless by-products are formed. The Pd/C catalyst proved to be efficient in the desired alkylation reactions however total deoxygenation could not be reached similarly to the results of P. Anbarasan and co-workers.10 To increase the hydrogenation reaction rate higher than atmospheric pressure was applied. In order to reach the total reduction of ketones or alcohols further development of a new efficient catalyst system is a must. Any alkenes or unsaturated ketones could not be detected, thus the used carbon support proved to be inert. Without bases (K3PO4 or CsOH) over Pd/C much lower alkylation activity (approx. half of the conversion than it was measured on catalysts containing both active components) can be observed. Pd-free catalysts containing only bases (K3PO4 or CsOH) show only less than tenth of activity obtained on catalysts loaded both active components. In presence of hydrogen by splitting the C-C bonds of the reactants lower concentration undesired methane and carbon monoxide gases are producing. It is interesting that the reactant acetone can be fully reduced to isopropyl alcohol already below 200 °C, but after all alkylation is materialized. Using hydrogen, significant butanol formation can be detected. In situ formed butanol results in mimicking of ABE mixture. Gaseous, cracked by-products are formed in less quantity by applying hydrogen stream over the applied "bifunctional" catalysts which is only the advantage of H2 use. Based on products shown in Tables 1 and 2 and the traces detectable by GC-MS a complex reaction scheme can be recognized; the main variation of the alkylation reactions are presented (Scheme 1), but several products are forming in low concentration as well. The yield of alkylated products is increasing at higher temperature, but at a lower temperature the production of useless gaseous by-products is less (Fig. 2). The efficiencies of the studied Pd/C catalysts (5Pd,20K3PO4/AC; 5Pd,20CsOH/AC) applied in different medium (He and H2) can be more easily compared in Fig. 2. The nature of different bases (CsOH or K3PO4) seems to be not too important in contrast to the batch results.10 However, it is a great difference that in this work the reaction temperature was much higher and gas/solid interactions were studied resulting in higher reaction rates and productivity with more than one magnitude of order. Figure 2. The sum of alkylated main product yields (■,□,•,0) and gaseous by-products (T,A,X,A) against the reaction temperature over 5Pd,20K3PO4/AC (^,A,A) and 5Pd,20CsOH/AC (•,0,T,X) in H2 (solid) and He (open). (WHSV=1 gAE h-1 gcat-1; p=21 bar; A/E=1:2 mol/mol) ' The di-alkylated products were formed in a consecutive reaction from mono-alkylated products as reflected in Figs. 3-4. Determination of optimal reaction conditions for the requested products needs compromise. Enhancement of the reaction temperature results in higher yields of the desired alkylates but with higher increase of gaseous by-products. Using longer catalyst bed or feeding less reactant by increasing the space time the yield for desired products are increasing with slow increase of gaseous byproducts yield resulting in better selectivity. Figure 3. Yield of significant products (■ 2-pentanone, • 4-hepta-none, ▲ 2-heptanone, ▼ 4-nonanone, ♦ gas by-products, + sum of main alkylates) obtained over 5Pd,20CsOH/AC catalyst in helium as a function of space time. The reaction was carried out at 21 bar total pressure and 300 °C. Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over ... 256 Acta Chim. Slov. 2016, 63, 251-257 Figure 4. Yield of significant products obtained (■ 2-pentanone, • 4-heptanone, □ 2-pentanol, O 4-heptanol, ▲ 2-heptanone, ▼ 4-nonanone, ♦ gas by-products, + sum of main alkylates) over 5Pd,20CsOH/AC catalyst in hydrogen as a function of space time. The reaction was carried out at 21 bar total pressure and 300 °C. 4. Conclusions Alkylation of ABE mixture reveals an exciting synergy of the reacting compounds in a complicated reaction network resulting in a complex liquid product (longer ke-tones (and alcohols in H2 atmosphere)) with decreased O-content and consequently with higher value. Guerbet alkylation is a green chemical process because water is the sole by-product. It proceeds in a reaction sequence of dehydrogenation-condensation-hydrogenation. In principle, the reaction does not require reducing agents (expensive hydrogen) for deoxygenation because great part of oxygen is removed in dehydration steps producing water. The catalyst initiates alcohol dehydrogenation (alcohol oxidation) aldol addition/condensation and hydrogenation of the obtained unsaturated ketone. The hydrogenation consumes the hydrogen obtained in the oxidation step, i. e., the metal sites catalyze the transfer dehydrogenation of alcohol and hydrogenation of condensation products as intermediates (hydrogen borrowing methodology). Pd/carbon catalysts have great potential for C-alkylation of ketones using alcohols via borrowing hydrogen route applied in batch or continuous processes equally. Working over fixed catalyst bed, presence of palladium and base crystallites together on well-defined activated carbon surface is advantageous resulting in high productivity, exceeding the cited results. Various mono- or dialkylated keto-nes were formed with high yields in inert, helium atmosphere and these products were found to be reducible selectively to alcohols over the same catalysts in hydrogen. This study gives a good base for efficient processing of ABE mixture (obtainable from biomass degradation) to fuel precursors in a continuous process using metal and alkaline loaded carbon supported catalysts (e.g. Pd,Cs-OH/AC). 5. Acknowledgements Thanks are due to the National Development Agency (Grant No. KTIA_AIK_12-1-2012-0014) for supporting this research work. 6. References 1. G.W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106(9), 4044-4098. http://dx.doi.org/10.1021/cr068360d 2. D. Kubicka, Collect. Czech. Chem. Commun. 2008, 73, 1015-1044. http://dx.doi.org/10.1135/cccc20081015 3. S. N. Naik, V. V. Goud, P. K. Rout, A. K. Dalai, Renew. Sustain. Energy Rew. 2010, 14, 578-597. http://dx.doi.org/10.1016Zj.rser.2009.10.003 4. H. N. Chang, N. J. Kim, J. Kang, C. M. Jeong, Biotechn. Bioproc. Eng. 2010, 15(1), 1-10. http://dx.doi.org/10.1007/s12257-009-3070-8 5. M. T. Holtzapple, C. B. Granda, Appl. Biochem. Biotechnol. 2009, 156(1-3), 525-536. http://dx.doi.org/10.1007/s12010-008-8466-y 6. V. Pham, M. T. Holtzapple, M. El-Halwagi, J. Ind. Microbiol. Biotechnol. 2010, 37(11), 1157-1168. http://dx.doi.org/10.1007/s10295-010-0763-0 7. Gy. Onyestyak, Catal. Commun. 2013, 38, 50-53. http://dx.doi.org/10.1016/j.catcom.2013.04.018 8. S. B. Bankar, G. Jurgens, S. A. Survase, H. Ojamo, T. Granström, Fuel, 2014, 136, 226-232. http://dx.doi.org/10.1016/j.fuel.2014.07.061 9. S. Nahreen, R. B. Gupta, Energy Fuels 2013, 27, 2116-2125. http://dx.doi.org/10.1021/ef302080n 10. P. Anbarasan, Z. C. Baer, S. Sreekumar, E. Gross, J. B. Binder, H. W. Blanch, D. S. Clark, F. D. Toste, Nature 2012, 491, 235-239. http://dx.doi.org/10.1038/nature11594 11. M. Dixit, M. Mishra, P. A. Joshi, D. O. Shah, Catal. Commun. 2013, 33, 80-83. http://dx.doi.org/10.1016/j.catcom.2012.12.027 12. Y. Obora, ACS Catal. 2014, 4, 3972-3981. http://dx.doi.org/10.1021/cs501269d 13. K. Shimizu, Catal. Sci. Technol. 2015, 5, 1412-1427. http://dx.doi.org/10.1039/C4CY01170H 14. G. Xu, Q. Li, J. Feng, Q. Liu, Z. Zhang, X. Wang, X. Zhang, X. Mu, Chem. Suc. Chem. 2014, 7, 105-109. http://dx.doi.org/10.1002/cssc.201300815 15. Q. Xu, J. Chen, H. Tian, X. Yuan, S. Li, C. Zhou, J. Liu, An-gew. Chem. Int. Ed. 2014, 53, 225-229. http://dx.doi.org/10.1002/anie.201308642 16. Sz. Harnos, Gy. Onyestyak, D. Kallo, Micropor. Mesopor. Mat. 2013, 167, 109-116. http://dx.doi.org/10.1016/j.micromeso.2012.03.011 Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over Acta Chim. Slov. 2016, 63, 251-257 257 Povzetek Pridobivanja možnih goriv iz biomase z zveznim procesiranjem mešanice aceton-butanol-etanol (ABE) smo proučevali z alkilacijo acetona z etanolom kot modelnima reaktantoma. Da bi lahko zasledovali kompleksnost reakcijskega mehanizma, butanola kot reaktanta v raziskavo nismo vključili. Uporabili smo pretočni reaktor v temperaturnem območju 150-350 °C s pretokom inertnega He ali reducenta H2. Reakcija je potekala ob prisotnosti katalizatorja, ki smo ga pripravili iz Pd in bazičnih (K3PO4 ali CsOH) kristalitov z uporabo komercialnega aktivnega ogljika. Katalizator smo predhodno tretirali v toku H2 pri temperaturi 350 °C. Tako smo z visokim izkoristkom pridobili mono- in dialkilirane ketone ki se lahko reducirajo le do alkoholov. Novodarszki et al.: Catalytic Alkylation of Acetone with Ethanol Over 258 Acta Chim. Slov. 2016, 63, 258-262 DOI: 10.17344/acsi.2015.2006 Scientific paper The Octyltrimethylamonium Bromide Adsorption at the Mercury Electrode / NaClO4 Solution Interface Dorota Gugala-Fekner,* Jolanta Nieszporek and Dorota Sieiiko Department of Analytical Chemistry and Instrumental Analysis, Faculty of Chemistry, Maria Curie-Sktdowska University, Maria Curie-Sktodowska Sq.3, 20-031 Lublin, Poland * Corresponding author: E-mail: gugala@poczta.umcs.lublin.pl Tel.: (48) 815375557 Received: 22-09-2015 Abstract The behaviour of octyltrimethylammonium bromide electrosorption on the mercury electrode in 1 mol/L NaClO4 was determined by means of double layer differential capacity measurements. The adsorption constants were derived from surface pressure data as a function of electrode charge density and cationic surfactant bulk concentration. Adsorption of octyltrimethylammonium bromide was analyzed using constants obtained from Frumkin, corrected Flory-Huggins and virial isotherms. It was found that the repulsive interactions for electrode charges close to 0 were the weakest between the adsorbed cations C11H26N+. In these conditions the surface concentration of the studied surfactant was the greatest. Keywords: adsorption isotherm, cationic surfactant, differential capacity, mercury electrode 1. Introduction The electrosorption of surfactants is important in a variety of fields, since they are used in electrocatalysis and electroanalysis. The fundamental and practical aspects of surfactant adsorption at various interfaces have received considerable attention thanks to their importance in many industrial processes. Quaternary ammonium compounds as cationic surfactants are used as inhibitors of steel corrosion in the acidic environment.1-3 In most cases the application of surfactants is dominated by empirical knowledge. However, for new technologies basic knowledge of the mode of their adsorption mechanism is required. One of the main aspects concerning the use of surfactants is the control of surface energy of the adsorbent. Based on adsorption isotherms the changes of such energy, the amount of surfactant adsorbed per unit area of adsorbent and the adsorption mechanism can be determined.4-8 Some authors investigated the adsorption of cationic surfactants on mercury.9,10 Mercury surface homogeneity and purity provide excellent reproducibility of adsorption phenomena. Solid electrodes (noble metals, different forms of carbon) have much narrower cathodic potential windows and thus cannot compete with mercury in this region.11The adsorption of phenols,12 thiourea derivatives,1317 and tert-butanol18 as well as coadsorption of butan-1-ol and I- ions19 at the mercury electrode from sodium perchlorate solutions were studied. The aim of this work was to study the adsorption of octyltrimethylammonium cation, C11H26N+ at the dropping mercury electrode from 1 mol/L NaClO4 solution. We chose NaClO4 as a supporting electrolyte because ClO4- ions cause the strongest disruption in water structu-re.20 The chosen surfactant concentrations are lower than its critical micellar point. The double capacitance was chosen as the primary experimental quantity. It was proved that the inhibiting effect of octyltrimethylammonium bromide on the electrode reaction rate is caused not only by blocking the electrode surface.21 2. Experimental The differential capacity of the double layer C was measured using the ac impedance technique with an Autolab frequency response analyzer (Eco Chemie, Netherlands). The measurements were carried out at frequencies: 400, 800, 1200, 1600 and 2000Hz with the amplitude 5 mV. The equilibrium capacities were obtai- Fekner et al.: The Octyltrimethylamonium Bromide Adsorption Acta Chim. Slov. 2016, 63, 258-262 259 ned by extrapolation of the measured capacity versus square root of the frequency to zero frequency. The experiments were performed in a three-electrode system with a dropping mercury electrode as a working electrode, Ag/AgCl with saturated sodium chloride as a reference electrode, and a platinum spiral as a counter electrode. A controlled growth mercury drop electrode (CGMDE) manufactured by MTM Anko Poland was used. The potential of zero change, Ez was measured using a streaming electrode. The interfacial tension, yz at Ez was measured by the maximum-bubble pressure method according to Schiffrin.22 The charge density and surface tension for the studied systems: 1 mol/L NaClO4 + increasing concentration of C11H26NBr from 1 x 10-5 mol/L to 7.5 x 10-4 mol/L were derived by the back integration of differential capacity-potential dependencies. Analytical grade C11H26NBr (Sigma, 98%) and Na-ClO4 (Fluka) were used without any further purification. Water and mercury were double distilled before use. The solutions were deaerated by passing high purity nitrogen over the solutions during the measurements which were carried out at 298 ± 0.1K. 3. Results and Discussion 3. 1. Analysis of Experimental Data Figure 1 presents differential capacity curves obtained experimentally in 1 mol/L NaClO4 solution and with the addition of C11H26N+ to the solution. A decrease of differential capacity in a wide range of potentials from -200mV to -1150mV was caused by the addition of C11H26N+. The increase of the concentration of C11H26N+ caused a widening of that area of potentials towards negative values. At the same time, the value of the potential -200mV practically did not change. The obtained results showed strong adsorption of C11H26N+ on the mercury electrode. With the maximum concentration of C11H26N+, its desorption took place at the potential of E = -1550mV. This effect was undoubtedly the result of electrostatic interactions of the cation C11H26N+ with the differently charged surface of the mercury electrode. Figure 1. Differential capacity-potential curves of the double layer Hg/1 mol/L NaClO4 aqueous solution and with the addition of CjjH26N+ (concentrations as in the legend). Figure 2. Dependences of the electrode charge versus the electrode potential for the studied C11H26NBr concentrations. As not all of the obtained C-E curves converge at sufficiently negative potentials with the corresponding curve for the base solution the capacity versus potential data were numerically integrated from the point of Ez. The value of Ez changed from -461mV, for 1 mol/L NaClO4, to - 447mV for the base solution containing 7.5 x 10-4 mol/L C11H26N+. Such changes of Ez indicate the mechanism of cation adsorption C11H26N+ with the ammonium group directed to mercury. At the same time the Tz value decreased from 421mN ■ m1 for 1 mol/L NaClO4 to 402 mN ■ m1 for the base solution containing 7.5 x 10-4 mol/L C11H26N+. Figure 2 presents the dependences of the electrode charge versus the electrode potential for the studied C11H26N+ concentrations. The point of intersection of the obtained curves allows one to determine the parameters of the maximum adsorption for C11H26N+: Emax = -468mV, the surface charge of the electrode, amax = 0. At the same time, such a course of dependences amax = f (E) confirms the physical character of adsorption C11H26N+ on the mercury electrode. Fekner et al.: The Octyltrimethylamonium Bromide Adsorption 262 Acta Chim. Slov. 2016, 63, 258-260 3. 2. Adsorption Isotherms Due to the ionic nature of the surfactant for calculating the relative surface excess, r', we used the Parsons' auxiliary function: g = y + SE, described in our previous studies.23 As the adsorption of ClO4- ions was demonstrated earlier,20 the obtained values r describe the surface concentration only of C11H26N+ ions. The r values were determined according to Gibbs adsorption isotherm: r - RT rUtacJ, (1) surface excess at saturation, rs, was estimated by extrapolating the 1/T' vs. 1/c lines at different electrode charges to 1/c = 0. The obtained Ts value was 7.7 x 10-6 mol ■ m-2. The surface occupied by one C11H26N+cation, S (S=1/rs), was 0.216 nm2. Such a small S value may indicate the perpendicular orientation of the adsorbed cation. Figure 4 shows the linear test of the Frumkin isotherm for electrode charges -3 0 may be the effect of the inductive movement of the charge in the C11H26N+ cation. This is accompanied by strong repulsive interactions and small r values. The obtained AGo values are comparable with those calculated for tetramethylthiourea16,26 where chemisorp-tion occurs on the mercury electrode. That is why in the case of physically adsorbed C11H26N+ considerably high AGo values are quite surprising. However, in this case the discussion of chemical interactions between the adsorbate and the electrode is not justified, first of all because of the 4. Conclusions The following conclusions can be drawn; - Adsorption of the cationic surfactant C11H26N+ on the mercury electrode has the physical character. However, it is quite strong, as evidenced by the AGovalues. The new important achievement of the present study is that we managed to question the hitherto-existing opinions stating that physical adsorption is determined by low AGo values. Namely, we showed that on the mercury electrode at physical adsorption of surfactant molecules with high molar mass the AGovalues are not at all small but are comparable with those obtained for the chemisorption of tetra-methylthiourea. - The highest values of surface concentrations r are found in the vicinity of the electrode charge o = 0. Under these conditions the repulsive interactions between the adsorbed cations are the weakest ones and they facilitate the adsorption C11H26N+. - The intensity of repulsive interactions between the adsorbate cations for the distant charges from o = 0 may be the result of the adsorbate reorientation. This reorientation is more pronounced for o> 0 than for o< 0. - In the extreme negative potential region, the positively charged surfactant headgroups are bound to mercury and there are strong interactions between the surfactant alkyl chains that are oriented parallel to each other. The bromide ions may form bridges between the ammonium groups, stabilizing the adsorption film electrostatically. 5. References 1. T. Y. Soror, M. A. El-Ziady, Mater. Chem. Phys. 2002, 77, 697-703. http://dx.doi.org/10.1016/S0254-0584(02)00129-3 Fekner et al.: The Octyltrimethylamonium Bromide Adsorption 262 Acta Chim. Slov. 2016, 63, 258-262 2. T. Vasudevan, S. Muralidharan, S. Alwarappan, S.V. K. Iyer, Corros. Sci. 1995, 37, 1235-1244. http://dx.doi.org/10.1016/0010-938X(95)00028-I 3. M. M. Saleh, Mater. Chem. Phys. 2006, 98, 83-89. http://dx.doi.Org/10.1016/j.matchemphys.2005.08.069 4. M. J. Rosen, Surfactants and Interfacial Phenomena, 2nd ed., Wiley, New York, 1989. 5. M. Klin, J. Nieszporek, D. Sienko, D. Gugala-Fekner, J. Saba, Acta Chim. Slov. 2011, 58, 26-32. 6. J. Nieszporek, S. Afr. J. Chem. 2014, 67, 1-5. 7. D. Gugal-Fekner, J. Nieszporek, D. Sienko, Monatsh. Chem. 2015, 146, 541-545. http://dx.doi.org/10.1007/s00706-014-1382-7 8. J. Nieszporek, D. Sienko, D. Gugal-Fekner, M. Klin, Turk. J. Chem. 2012, 36, 841-851. 9. A. Avranas, A. Komnianou, U. Retter, J. Colloid Interface Sci. 2003, 264, 407-413. http://dx.doi.org/10.1016/S0021-9797(03)00534-4 10. A. Avranas, N. Sedlackova, E. Malasidon, J. Colloid Interface Sci. 2005, 285, 665-673. http://dx.doi.org/10.1016/jjcis.2004.12.015 11. J. Barek, Port. Electrochim. Acta. 2013, 31, 291-295. http://dx.doi.org/10.4152/pea.201306291 12. S. Sarangapani, V. K. Venkatesan, Proc.Indian Natn. Sci. Acad.-A, 1983, 49(1), 124-142. 13. A. Nosal-Wiercinska, G. Dalmata, Electrochim. Acta, 2006, 51(27), 6179-6185. http://dx.doi.org/10.1016Zj.electacta.2006.01.062 14. G. Dalmata, A. Nosal-Wiercinska, Croat. Chem. Acta, 2008, 81(4), 529-537. 15. N. Nosal-Wiercinska, G. Dalmata, Electrochim. Acta, 2006, 51(27), 6179-6185. http://dx.doi.org/10.1016/j.electacta.2006.01.062 16. D. Gugal, Z. Fekner, D. Sienko, J. Nieszporek, J. Saba, Elec-trochim. Acta, 2004, 49(14), 2227-2236. http://dx.doi.org/10.1016/j.electacta.2003.12.026 17. M. Klin, J. Nieszporek, D. Sienko, D. Gugal-Fekner, J. Saba, Croat. Chem. Acta, 2011, 84(4), 475-480. http://dx.doi.org/10.5562/cca1791 18. J. Nieszporek, Cent. Eur. J. Chem. 2013, 11(1), 86-93. http://dx.doi.org/10.2478/s11532-012-0137-8 19. J. Saba, K. Sykut, J. Nieszporek, J. Szaran, Collect. Czech. Chem. Commun., 1999, 64(12), 1925-1936. http://dx.doi.org/10.1135/cccc19991925 20. J. Koryta, J. Dworak, V. Bohackova, Lehrbuch der Elektrochemie, Springer-Verlag Wien, New York, 1975. http://dx.doi.org/10.1007/978-3-7091-8418-9 21. J. Nieszporek, J. Electroanal. Chem. 2013, 706, 108-116. http://dx.doi.org/10.1016/jjelechem.2013.08.007 22. D. J. Schiffrin, J. Electroanal. Chem. 1969, 23, 168-171. http://dx.doi.org/10.1016/S0022-0728(69)80203-2 23. D. Sienko, D. Gugal-Fekner, J. Nieszporek, Z. Fekner, J. Saba, Collect. Czech. Chem. Commun. 2009, 74, 1309-1321. http://dx.doi.org/10.1135/cccc2009007 24. W. R. Fawcett, R. C. Rocha-Filho, L. M. Doubova, J. Chem. Soc., Faraday Trans. 1991, 87, 2967-2970. http://dx.doi.org/10.1039/FT9918702967 25. S. Trassati, J. Electroanal. Chem. Interfacial Electrochem. 1970, 28, 257-277. http://dx.doi.org/10.1016/S0022-0728(70)80120-6 26. D. Gugal-Fekner, D.Sienko, J. Nieszporek, M. Klin, J. Saba, J. Colloid Interface Sci. 2009, 332, 291-297. http://dx.doi.org/10.1016/jjcis.2008.12.067 27. J. Lawrence and J. Parsons, J. Phys. Chem. 1969, 73, 35773581. http://dx.doi.org/10.1021/j100845a008 Povzetek Z meritvami diferencialne kapacitivnosti dvoplasti smo proučevali elektrosorpcijo oktil trimetil amonijevega bromida (CjjH26NBr) na Hg elektrodo v vodni raztopini 1 M NaClO4. Z uporabo Frumkinove, popravljene Flory-Hugginsove in virialne izoterme smo iz podatkov za površinski tlak v odvisnosti od gostote naboja na elektrodi in koncentracije sur-faktanta določili konstante adsorpcije. Izkazalo se je, da so pri naboju na elektrodi blizu 0 odbojne interakcije med ad-sorbiranimi kationi C11H26N+ najšibkejše. Pri teh pogojih je torej koncentracija preučevanega surfaktanta na površini največja. Fekner et al.: The Octyltrimethylamonium Bromide Adsorption DOI: 10.17344/acsi.2015.2096 Acta Chim. Slov. 2016, 63, 263-270 263 Scientific paper 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: As an Effective, New and Reusable Media for the Synthesis of 14-Aryl-14#-dibenzo[aj]xanthenes Leila Zare Fekri* and Hajar Saeedi Fard Department of Chemistry, Payame Noor University, PO Box 19395-3697 Tehran, Iran * Corresponding author: E-mail: chem_zare@yahoo.com Received: 02-11-2015 Abstract A general synthetic route to dibenzoxanthenes has been developed using 1,4-diazaniumbicyclo[2.2.2]octane diacetate as a new bis ionic liquid under thermal and solvent free condition. This method provides several advantages such as a simple work-up, environmental friendliness and shorter reaction time along with high yields. All of the synthesized compounds were characterized by infrared spectroscopy, 1H and 13C spectroscopy and elemental analyses. Keywords: Solvent free, xanthenes, 1,4-diazaniumbicyclo[2.2.2]octane diacetate, ß-naphthol 1. Introduction Research on xanthenes, especially benzoxanthenes, has emerged in organic synthesis due to their wide range of biological and therapeutic properties like antiviral,1 antiinflammatory,1 and antibacterial activities,1a,b as well as in photodynamic therapy2 and as antagonists of the paralyzing action of zoxazolamine.3 Xanthenes are also available from natural sources. Popularly known Santalin pigments have been isolated from a number of plant spe-cies.4 Furthermore, due to their useful spectroscopic properties they are used as dyes,5 in laser technologies,6 and in fluorescent materials for visualization of biomolecu-les.7 Many procedures have been disclosed on how to synthesize xanthenes and benzoxanthenes, such as cyclo-dehydrations,8 trapping of benzynes by phenols,9 alkyla-tions of hetero atoms,10 cyclocondensations between 2-hydroxyaromatic aldehydes and 2-tetralone.11 Benzal-dehydes and acetophenones bearing tethered carbonyl chains underwent the intramolecular phenyl-carbonyl coupling reactions in the presence of samarium diiodide and hexamethylphosphoramide to afford xanthenes.12 In addition, 14H-dibenzo[aj]xanthenes and related products are prepared by the reaction of P-naphthol with for-mamide,1 1-hydroxymethylnaphthalen-2-ol13 and carbon monoxide.14 Recently, xanthenes were also synthesized by the condensation of aldehydes, P-naphthol and dime- done.15 Due to the environmental concerns, the use of benign solvents as alternatives to the volatile organic solvents is of high interest to organic chemists. The use of ionic liquids as reaction media and catalyst can offer a solution to the solvent emission and catalyst recycle prob-lems.16,17 Ionic liquids possess the advantages, like negligible vapor pressure, reasonable thermal stability and recyclability. They dissolve many organic and inorganic substrates and are tunable to specific chemical tasks.18 Recently, ionic liquids have been successfully employed as solvents with concomitant catalytic activity for a variety of reactions.19 2. Results and Discussion As a part of our going interest for the development of efficient and environmentally friendly procedures for the synthesis of heterocyclic and pharmaceutical com-pounds,20-23 an efficient, facile and solvent free procedure was introduced for the synthesis of 14-aryl-14H-diben-zo[aj]xanthenes (Scheme 1). For this purpose, the reaction of aromatic aldehydes and P-naphthols using a bis ionic liquid (1,4-diazaniumbicyclo[2.2.2]octane diacetate, DABCO-diacetate), was investigated for the first time. The procedure presented here not only gives the desired products in good yields, but also avoids the problems associated with the conventional solvents such as cost, Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: 264 Acta Chim. Slov. 2016, 63, 263-270 handling, safety and pollution, and moreover the reaction times are reduced to a few minutes. To emphasize the effect of the ionic liquid, the model reaction between 4-chlorobenzaldehyde and P-napht-hol was described and different acid catalysts were tested for this reaction. All the reactions were run with catalytic amounts of the catalysts. As can be seen in Table 1 satisfactory results were obtained only with DABCO-diacetate (entry 9). To investigate the efficiency and generality of the reaction, various benzaldehyes were treated with P-napht-hol under the above-described reaction conditions in the presence of DABCO-diacetate. The results are summarized in Table 2. Accordingly, we can see that all the reactions afforded the corresponding xanthenes 3a-p in high yields. On the other hand, the synthesis of xanthenes from hydrazones required shorter reaction times and provided the products in higher yields than was the case when starting from aldehydes. It seems that the conversion of aldehydes to the corresponding hydrazone derivatives helps to facilitate the nucleophilic addition of P-naphthol in comparison with the starting aldehydes. Because the hydrazones are unstable under acidic ionic liquid media, it helps to treat them better with P-naphthol. After reaction, the ionic liquid was easily separated from the reaction medium by washing with distilled water (IL is soluble in water). The washed ionic liquid was distilled under vacuum to recover it and reuse it as a solvent in the subsequent reactions. After three successive runs, recycled ionic liquid showed no loss of efficiency with regard to the reaction time and yield (Table 3). Table 1. Effect of catalyst or media on the reaction of 4-chlorobenzaldehyde and P-naphthol Entry Catalyst Catalyst amount/ 1mmol of substrate Reaction conditions Time (min) Yield (%) 1 H2SO4 5 drops Reflux 7200 34 2 ^-TsOH 0.5 mmol Reflux 3600 45 3 Montmorillonite K10 0.5 g Reflux 120 81 4 HY-Zeolite 0.5 g Reflux 120 68 5 I2 0.5 mmol Reflux 7200 15 6 L-proline 0.5 mmol Reflux 3600 45 7 Nanoparticle Fe3O4 0.5 g Reflux 60 83 8 Nanoparticle Fe3O4 @SiO2 0.5 mmol Reflux 60 85 9 DBU-Ac 0.5 mmol Heat, 80 °C 10 82 10 DABCO-diacetate 0.5 mmol Heat, 80 °C 6 91 11 DABCO-diacetate 0.3 mmol Heat, 80 °C 8 85 12 DABCO-diacetate 0.5 mmol Heat, 60 °C 8 74 Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: Acta Chim. Slov. 2016, 63, 263-270 265 Table 2. Synthesis of 14-aryl-14ff-dibenzo[aj]xanthenes and comparison of efficiency of [DABCO]diacetate Entry Product" Procedure a Procedure b Time (min) Yield (%)b Time (min) Yield (%)b 1 5 94 3 98 310-311 1, 24, 25 6 91 3.5 97 287-288 1, 24, 25 6 89 4 95 294-295 1, 24,25 5.5 87 4 94 239-240 1, 24, 25 8 83 5 91 293-294 1, 24, 25 5 94 97 210-211 1 8 87 5.5 94 215-216 1, 24, 25 6 92 4 93 192-193 1, 24,25 2 3 4 5 6 3 7 8 Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: 266 Acta Chim. Slov. 2016, 63, 263-270 Entry Product" Procedure a Time (min) Yield (%)b Procedure b Time (min) Yield (%)b mp ( C) Ref. 6.5 94 5 98 262-263 1, 24, 25 10 10 87 6 93 145-146 1, 24, 25 11 9 89 5.5 95 227-228 1, 24, 25 12 10 86 6 92 205-206 1, 24, 25 13 12 82 8 90 260-261 1, 24, 25 14 8 80 6 85 181-182 1, 24, 25 15 12 89 7 96 194-196 25 16 13 85 7 95 189-190 9 a All products were characterized by the comparison of their physical constants with those of authentic samples and by the help of IR and NMR spectroscopy. b Yields based upon the starting aldehyde. Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: Acta Chim. Slov. 2016, 63, 263-270 267 Table 3. Evaluation of reusability of the ionic liquid for the synthesis of 3b Run 1 2 3 4 5 Time (min) 6 6 6 7 7 Yield (%) 91 90 88 90 88 m.p. (°C) 287-288 287-289 288-290 287-288 287-289 In the proposed mechanistic pathway, initially the aldehyde and P-naphthol are activated via dipolarization by DABCO-diacetate, followed by the nuclophilic attack of 2 equivalents of the P-naphthol to activate the aldehyde and finally via dehydration, the product 3 is produced. To investigate the efficiency of this method, the comparison between this method and some of those previous reported for the synthesis of 3b was carried out (Table 4). 12H), 14.11 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3): 5 21.9, 44.5, 175.8 ppm. 3. 2. General Procedure for the Preparation of 3a-n A mixture of the aldehyde (1 mmol), P-naphthol (2 mmol) and [DABCO]diacetate (0.5 mmol) was heated at 80 °C for the required reaction time according to the Table 1. After completion of the reaction, as indicated by TLC, the reaction product was extracted by CHCl3/H2O. After evaporation of the organic solvent, the crude product was obtained and recrystallized from EtOH and dried to afford the compounds 3a-p as powders. The filtrate was concentrated under reduced pressure and washed with diethyl ether. Then, it was dried in a Table 4. Comparison of synthesis of compound 3b in this method with some of the previously reported methods Entry Catalyst Condition Time (min) Yield (%) Ref. 1 Selectfluor™ stir at 125 °C 420 95 1 2 Polytungstozincate acid 80 °C/Solvent-free 90 88 24 3 CoPy2Cl2 85 °C, neat conditions 120 95 25 4 Alum Water, 100 ° C 240 90 26 5 SiO2-ZnCl2 Stir, 100°C 40 83 27 6 [Et3N-SO3H ]Cl Sonication, 80 °C 40 93 28 7 Mg(BF4)2 doped in [BMim][BF4] Neat, 80 °C 15 94 29 8 DABCO-dihydroAc procedure a 6 91 This work 9 DABCO-dihydroAc Procedure b 3.5 97 This work 3. Experimental Chemicals were purchased from Merck and Fluka. All solvents used were dried and distilled according to the standard procedures. Melting points were measured on an Electrothermal 9100 apparatus. IR spectra were determined on a Shimadzu FT-IR 8600 spectrophotometer. 1H and 13C NMR spectra were determined on a Bruker 400 DRX Avance instrument at 400 and 100 MHz, respectively. Elemental analyses were recorded on a Carlo-Erba EA1110CNNO-S analyzer. 3. 1. Preparation of 1,4-Diazaniumbicyclo [2.2.2]octane diacetate, [DABCO] diacetate, as a Novel Bis Ionic Liquid A mixture of 1,4-diazabicyclo[2.2.2]octane (10 mmol) and acetic acid (20 mmol) was irradiated with microwaves (180 W) for 2 min at 100 °C three times. After completion of the reaction, the mixture was washed with diethyl ether (3 x 10 mL). The organic product was extracted from the liquid phase and evaporated under vacuum to produce the desired ionic liquid. Analytical data for DABCO-diacetate: yellow oil. 1H NMR (400 MHz, CDCl3): 5 2.16 (s, 2H), 3.01 (s, vacuum evaporator to recover the ionic liquid for the subsequent use. 3. 3. Analytical Data for the Synthesized Compounds 14-(4-Nitrophenyl)-14_ff-dibenzo[a.j]xanthene (3a): yellow solid; m.p. 310-311 °C; IR (KBr) v 3065, 1623, 1554, 1352, 1221 cm-1; 1H NMR (400 MHz, CDCl3) 5 6.7 (s, 1H), 7.69-8.05 (m, 12H), 8.34 (d, J = 8.7 Hz, 2H), 8.58 (d, J = 8.2 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 38.9, 121.8, 122.5, 125.2, 126.5, 127.1,131.8, 132.4, 132.9, 135.2, 136.5, 136.6, 136.9, 147.3, 151.9 ppm; Anal Calc. for C27H17NO3: C, 80.38; H, 4.25; N, 3.47. Found: C, 80.43; H, 4.21, N, 3.52. 14-(4-Chlorophenyl)-14_ff-dibenzo[a.j ]xanthene (3b): Brown solid; m.p. 287-288 °C; IR (KBr) v 3068, 1646, 1556, 1487, 1233, 1121 cm-1. 1H NMR (400 MHz, CDCl3) 5 6.49 (s, 1H), 7.12 (dd, J = 2.0 Hz, J = 6.4 Hz, 2H), 73.42-7.45 (m, 2H), 7.46-7.49 (m, 2H), 7.51 (s, 2H), 7.58-7.62 (m, 2H), 7.82 (d, J = 9.2 Hz, 2H), 7.86 (d, J = 8.0 Hz, 2H), 8.34 (d, J = 8.4 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 36.7, 115.9, 119.0, 124.9, 126.3, 126.9, 130.2, 130.3, 133.0, 134.5, 135.7, 139.2, 139.8, 146.1, Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: ... 268 Acta Chim. Slov. 2016, 63, 263-270 151.4 ppm; Anal. Calcd for C27H17ClO: C, 82.54; H, 4.36. Found: C, 82.58; H, 4.29. 14-(4-Bromophenyl)-14ff-dibenzo[a.j]xanthene (3c): Brown solid; m.p. 294-295 °C; IR (KBr) v 3123, 1654, 1537, 1481, 1223, 1126 cm-1. 1H NMR (400 MHz, CDCl3) 5 6.74 (s, 1H), 7.35 (d, J = 8.4 Hz, 2H), 7.48 (t, J = 7.2 Hz, 2H), 7.56-7.66 (m, 6H), 7.95 (d, J = 8.8 Hz, 4H), 8.66 (d, J = 8.4 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 35.8, 112.9, 118.3, 125.1, 126.7, 126.8, 131.9, 132.3, 133.6, 134.9, 135.0, 139.1, 140.8, 145.2, 153.5 ppm; Anal. Calcd for C27H17BrO: C, 74.15; H, 3.92. Found: C, 74.09; H, 3.99. 27 17 14-(2-Nitrophenyl)-14_ff-dibenzo[a./]xanthene (3e): Yellow solid; m.p. 293-294 °C; IR (KBr) v 3354, 3018, 1625, 1556, 1367, 1289, 1109 cm-1; 1H NMR (400 MHz, CDCl3) 5 6.57 (s, 1H), 7.23-8.76 (m, 16H); 13C NMR (100 1MHz, CDCl3) 5 34.7, 119.2, 121.4, 123.5, 124.9, 125.0, 126.4, 129.0, 130.4, 130.8, 131.9, 133.9, 136.6, 137.2, 143.3, 145.5, 150.2 ppm; Anal. Calcd for C27H17NO3: C, 80.38; H, 4.25; N, 3.47. Found: C, 80.42; H, 4.20, N, 3.51. 14-(3-Nitrophenyl)-14_ff-dibenzo[a,/]xanthene (3f): Yellow solid; m.p. 210-211 °C; IR (KBr) v 3054, 2936, 1556, 1489, 1343, 1223 cm-1; 1H NMR (400 MHz, CDCl3) 5 6.55 (s, 1H), 7.23-7.81 (m, 13H), 8.32 (d, J = 8.5 Hz, 2H), 8.56 (s, 1H) ppm; 13C NMR (100 MHz, CDCl3) 5 34.7, 119.2, 121.4, 123.5, 125.0, 126.4, 129.0, 130.43 130.8, 131.9, 133.7, 133.9, 136.6, 137.2, 143.3, 145.5, 150.2 ppm; Anal. Calcd for C27H17NO3: C, 80.38; H, 4.25; N, 3.47. Found: C, 80.34; H, 44.227, N, 3.54. 14-(3-Bromophenyl)-14_ff-dibenzo[a./]xanthenes (3h): Yellow solid; m.p. 192-193 °C; IR (KBr) v 3015, 2926, 1612, 1476, 1321, 1212 cm-1; 1H NMR (DMSO-d6, 400 MHz) 5 6.61 (s, 1H), 6.65-7.11 (m, 2H), 7.32 (d, J= 7.6 Hz, 2H), 7.51-7.53 (m, 5H), 7.65-7.81 (m, 2H), 7.85-7.89 (m, 4H), 8.14 (d, J = 7.8 Hz, 1H); 13CNMR (DMSO-d6, 100 MHz) 5 32.1, 114.3, 115.4, 123.3 (two carbons), 128.9, 129.1, 129.3, 129.7 (two carbons), 129.8, 130.5, 130.6, 130.9, 131.8, 132.2, 145.5, 149.6 ppm; Anal. Calcd for C27H17BrO: C, 74.15; H, 3.92. Found: C, 74.25; H, 3.94. 27 17 14-(3-Fluorophenyl)-14_ff-dibenzo[a./]xanthene (3i): Brown solid; m.p. 262-263 °C; IR (KBr) v 3143, 1568, 1412, 1254, 1117, 1078 cm-1; 1H NMR (400 MHz, CDCl3) 5 6.51 (s, 1H), 6.77-8.24 (m, 16H) ppm; 13C NMR 3(100 MHz, CDCl3) 5 37.3, 113.0, 113.5, 116.1 (d, 3JC F = 2.6 Hz), 117.1, 119.8, 120.1, 121.9, 124.3 (d, 3JC F = 2.8 Hz), 124.8, 128.0, 129.1, 129.7, 130.1 (d, 2JCF = 28.3 Hz), 134.5 (d, 2JC-F = 33.4 Hz), 147.8 (d, = 160.2 Hz), 151.2 ppm; Anal.Calcd for C27H17FO: C, 86.15; H, 4.55; F, 5.05. Found: C, 86.09; H, 4.54. 14-(4-Hydroxyphenyl)-14_ff-dibenzo[a.j]xanthene (3j): Pink solid; m.p. 145-146 °C; IR (KBr) v 3414, 1609, 1512, 1464, 1235, 1123 cm-1; 1H NMR (400 MHz, CDCl3) 5 4.76 (br, s, 1H), 6.37(s, 1H), 6.52-8.87 (m, 16H) ppm; 13C NMR (100 MHz, CDCl3) 5 34.3, 116.7, 118.0, 118.4, 123.2, 124.6, 126.1, 126.7, 128.4, 130.8, 132.4, 132.8, 139.9, 146.8, 157.1 ppm; Anal. Calcd for C27H18O2: C, 86.61; H, 4.85. Found: C, 86.63; H, 4.78. 14-(4-Methylphenyl)-14_ff-dibenzo[a./]xanthene (3k): White solid; m.p. 227-228 °C; IR (KBr) v 3013, 2923,1634, 1589, 1487, 1492, 1233 cm-1; 1H NMR (400 MHz, CDCl3) 5 2.32 (s, 3H), 6.42 (s, 1H), 6.78 (d, J = 9.6 Hz, 2H), 7.54-8.09 (m,12H), 8.43 (d, J = 8.9 Hz, 2H) ppm; 13C NMR (100 MHz,CDCl3) 5 23.1, 36.2, 113.6, 117.1, 126.2, 126.7, 128.2, 129.5, 131.4, 132.2, 133.2, 134.1, 144.8, 148.6, 149.8, 151.5 ppm; Anal. Calcd for C28H20O: C, 90.29; H; 5.41. Found: C, 90.34; H; 5.42. 14-(4-Methoxyphenyl)-14_ff-dibenzo[a.l/]xanthene (3l): yellow solid; m.p. 205-206 °C; IR (KBr) v 3123, 2876, 1675, 1609, 1588, 1437, 1387, 1276 cm-1; 1H NMR (400 MHz, CDCl3) 5 3.53 (s, 3H), 6.54 (s, 1H), 6.73 (d, J = 8.7 Hz, 2H),7.56-7.76 (m, 12H), 8.67 (d, J = 8.7 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 36.9, 53.2, 112.6, 117.8, 118.9, 124.0, 124.1, 126.8, 129.1, 127.8, 130.9, 137.0, 137.8, 151.3, 152.5, 153.2 ppm; Anal. Calcd for C28H20O2: C, 86.57; H; 5.19. Found: C, 86.41; H; 5.20. 14-Phenyl-14ff-dibenzo[a,/']xanthene (3n): White solid; m.p. 181-183 °C; IR (KBr) v 3089, 2911, 1623, 1580, 1542, 1437, 1256, 1177cm-1; 1H NMR (400 MHz, CDCl3) 5 6.51 (s, 1H), 6.98-7.02 (m, 1H), 7.14-7.18 (m, 2H), 7.40-7.44 (m, 2H), 7.50 (d, J = 8.8 Hz, 2H), 7.53-7.55 (m, 2H), 7.59-7.61 (m, 2H), 7.81 (d, J = 8.8 Hz, 2H), 7.84 (d, J = 8.0 Hz, 2H), 8.40 (d, J = 8.4 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 31.3, 114.2 (two carbons), 121.2,123.5, 125.6, 127.8 (two carbons), 129.1 (two carbons), 133.4, 135.6, 145.2, 149.3, 159.1 ppm; Anal. Calcd for C27H18O: C, 90.47; H, 5.06. Found: C, 90.41; H, 5.13. 3-(14_ff-Dibenzo[a,j]xanthen-14-yl)chromen-4-one (3o): Light yellow solid; m.p. 194-196 °C; IR (KBr) v 3143, 1623, 1576, 1423, 1278, 1208, 1181 cm-1; 1H NMR (400 MHz, CDCl3) 5 6.10 (s, 1H), 6.52 (s, 1H), 7.56-8.05 (m, 16 H) ppm; 13C NMR (100 MHz, CDCl3) 5 36.7, 55.4, 112.2, 114.3, 117.6, 118.1, 118.5, 118.9, 123.6, 125.2, 129.8, 131.2, 133.7, 136.1, 139.6, 143.1, 147.4, 151.3, 161.1 ppm; Anal. Calcd for C30H18O3: C, 84.49; H, 4.25. Found: C, 84.37; H, 4.21. 30 14-(4-N,N-Dimethylphenyl)-14fl-dibenzo[a,/']xanthene (3p): yellow solid; m.p. 189-190 °C; IR (KBr) v 3112, 1632, 1514, 1445, 1232, 1212, 1209, 1123 cm-1. 1H NMR (400 MHz, CDCl3) 5 3.01 (s, 6H), 6.83 (s, 1H), 7.39-7.49 Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: Acta Chim. Slov. 2016, 63, 263-270 269 (m, 3H), 7.54-7.67 (m, 4H), 7.78-7.85 (m, 3H), 7.91-7.99 (m, 2H), 8.03 (d, J = 9.2 Hz, 1H), 8.20 (s, 1H), 8.69 (d, J = 8.4 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3) 5 34.2, 75.2, 113.2, 115.1, 117.6, 118.1, 119.1, 122.7, 125.3, 129.8, 130.9, 134.8, 143.1, 144.6, 149.1, 163.2 ppm; Anal. Calcd for C29H23NO: C, 86.75; H, 5.77; N, 3.49. Found: C, 86.77; H, 5.56; N, 3.65. 4. Conclusion In conclusion, we have investigated the ionic liquid 1,4-diazaniumbicyclo[2.2.2]octane diacetate as a mild and efficient media for the synthesis of substituted 14-aryl-14H-dibenzo[aj]xanthenes. The remarkable advantages offered by this method are: the catalyst is inexpensive, non-toxic, easy to handle and reusable, alowing simple work-up procedure, short reaction times, high yields of the products with better purity and offers green aspects by avoiding toxic catalysts and hazardous solvents. To the best of our knowledge this is the first report on synthesis of alkyl- or aryl-14H-dibenzo[a,;]xanthene derivatives using ionic liquid 1,4-diazaniumbicyclo[2.2.2]octane diacetate. 5. Acknowledgement Financial support from the Research Council of Payame Noor University of Rudsar branch is sincerely acknowledged. 6. References 1. (a) P. S. Kumar, B. Sunil Kumar, B. Rajitha, P. Narsimha Reddy, N. Sreenivasulu, Y. Thirupathi Reddy, Arkivoc 2006, (xii), 46-50; (b) V. S. Patil, V. S. Padalkar, K. R. Phatangare, P. G. Umape, B. N. Borase, N. Sekar, J. Heterocycl. Chem. 2015, 52, 124-129. http://dx.doi.org/10.1002/jhet.1998 2. R. M. Ion, D. Frackowiak, A. Planner, K. Wiktorowicz, Acta Biochim. Pol. 1998, 45, 833-845. 3. G. Saint-Ruf, H. T. Hieu, J. P. Poupelin, Naturwissenschaften 1975, 62, 584-585. http://dx.doi.org/10.1007/BF01166986 4. (a) A. Arnone, L. Merlini, G. Nasini, Tetrahedron Lett. 1972, 13, 3503-3506; http://dx.doi.org/10.1016/S0040-4039(01)94083-3 (b) B. Ravindranath, T. R. Sheshadri, Phytochemistry 1973, 12, 2781-2790; http://dx.doi.org/10.1016/0031-9422(73)85099-X (c) J. Kinjo, H. Uemura, T. Nohara, M. Yamashita, N. Maru-bayashi, K. Yoshihira, Tetrahedron Lett. 1995, 36, 55995602. http://dx.doi.org/10.1016/00404-0399(50)10710- 5. A. Banerjee, A. K. Mukherjee, Stain Technol. 1981, 56, 83-85. http://dx.doi.org/10.3109/10520298109067286 6. M. Ahmad, T. A. King, K. Ko Do, B. H. Cha, J. J. Lee, Phys. D: Appl. Phys. 2002, 35, 1473-1476. http://dx.doi.org/10.1088/0022-3727/35/13/303 7. C. G. Knight, T. Stephens, Biochem. J. 1989, 258, 683-661. http://dx.doi.org/10.1042/bj2580683 8. (a) A. Bekaert, J. Andrieux, M. Plat, Tetrahedron Lett. 1992, 33, 2805-2806; http://dx.doi.org/10.1016/S0040-4039(00)78863-0 (b) J. Sarma, J. B. Baruah, Dyes Pigm. 2005, 64, 91-92. http://dx.doi.org/10.1016Zj.dyepig.2004.03.010 9. D. W. Knight, P. B. Little, Synlett 1998, 1141-1143. http://dx.doi.org/10.1055/s-1998-1878 10. (a) R. Vazquez, M. C. de la Fuente, L. Castedo, D. Domínguez, Synlett 1994, 433-434; http://dx.doi.org/10.1055/s-1994-22878 (b) H. Ishibashi, K.Takagaki, N. Imada, M. Ikeda, Synlett 1994, 49-50. http://dx.doi.org/10.1055/s-1994-22734 11. A. Jha, J. Beal, Tetrahedron Lett. 2004, 45, 8999-9001. http://dx.doi.org/10.1016/j.tetlet.2004.10.046 12. C.-W. Kuo, J.-M. Fang, Synth. Commun. 2001, 31, 877-892. http://dx.doi.org/10.1081/SCC-100103323 13. R. N. Sen, N. N. Sarkar, J. Am. Chem. Soc. 1925, 47, 1079-1091. http://dx.doi.org/10.1021/ja01681a023 14. K. Ota, T. Kito, Bull. Chem. Soc. Jpn. 1976, 49, 1167-1168. http://dx.doi.org/10.1246/bcsj.49.1167 15. M. A. Ghasemzadeh, Acta. Chim. Slov. 2015, 62, 977-985. http://dx.doi.org/10.17344/acsi.2015.1501 16. T. Welton, Chem. Rev. 1999, 99, 2071-2084. http://dx.doi.org/10.1021/cr980032t 17. R. Sheldon, Chem.Commun. 2001, 2399-2407. http://dx.doi.org/10.1039/b107270f 18. J. K. Lee, M. J. Kim, J.Org.Chem. 2002, 67, 6845-6847. http://dx.doi.org/10.1021/jo026116q 19. T. S. Li, Z. H. Zhang, F. Yang, C. G. Fu, J. Chem. Res. 1998, 1, 38. http://dx.doi.org/10.1039/a703694i 20. L. Synth. Commun. 2011, 41, 2323-2330. http://dx.doi.org/10.1080/00397911.2010.502990 21. M. Nikpassand, L. Zare, M. Saberi, Monatsh. Chem. 2012, 143, 289-293. http://dx.doi.org/10.1007/s00706-011-0575-6 22. L. Zare, N.O. Mahmoodi, A.Yahyazadeh, M. Nikpassand, Ultrason. Sonochem. 2012, 19, 740-744. http://dx.doi.org/10.1016/j.ultsonch.2011.11.008 23. L. Zare Fekri, M. Nikpassand, K. Hassanpour, Curr. Org. Syn. 2015, 12, 76-79. http://dx.doi.org/10.2174/1570179411666140806005614 24. M. Mohammadpour Amini, Y. Fazeli, Z. Yassaee, S. Feizi, A. Bazgir, Open Catal .J. 2009, 2, 40-44. http://dx.doi.org/10.2174/1876214X00902010040 25. J. Venu Madhav, B. Suresh Kuarm, B. Rajitha, Arkivoc 2008, (ii), 204-209. 26. M. Baghbanzadeh, M. Shakouri Nikchen, E. Arzroomchilar, Bioorg. Med. Chem. Lett. 2008, 18, 436-438. http://dx.doi.org/10.1016/j.bmcl.2007.07.008 27. H. A. Soliman, A. Y. Mubarak, A. El-Mekabati, S. S. El-morsy, Chem. Sci. Trans. 2014, 3, 819-825. Fekri and Fard: l,4-Diazaniumbicyclo[2.2.2]octane Diacetate: 270 Acta Chim. Slov. 2016, 63, 263-270 28. A. Zare, A. R. Moosavi-Zare, M. Merajoddin, M. A. Zolfi-gol, T. Hekmat-Zadeh, A. Hasaninejad, A. Khazaei, M. Mokhlesi, V. Khakyzadeh, F. Derakhshan-panah, M. H. Bey-zavi, E. Rostami, A. Arghoon, R. Roohandeh. J. Mol. Liq. 2012, 167, 69-77. http://dx.doi.org/10.10167j.molliq.2011.12.012 29. K. Rad-Moghadam, S. C. Azimi, J. Mol. Catal. 2012, 363, 465-469. http://dx.doi.org/10.10167j.molcata.2012.07.026 Povzetek Razvili smo splošno sintezno pot do dibenzoksantenov z uporabo 1,4-diazanijumbiciklo[2.2.2]oktan diacetata kot nove bis ionske tekočine pod termičnimi pogoji brez prisotnosti topil. Ta metoda predstavlja kar nekaj prednosti, kot so enostavnost izolacije, okoljska sprejemljivost in krajši reakcijski časi ob hkratnem doseganju višjih izkoristkov. Vse sinteti-zirane spojine smo karakterizirali s pomočjo infrardeče spektroskopije, 1H in 13C magnetne resonančne spektroskopije in elementnih analiz. Fekri and Fard: 1,4-Diazaniumbicyclo[2.2.2]octane Diacetate: DOI: I0.i7344/acsi.20i5.2ii5_Acta Chim. Slov. 2016, 63, 271-278_ 271 Scientific paper Substitution Reactions of the Aluminum Chlorogermylenoid H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 Bingfei Yan, Mingxia Zhang, Wenzuo Li,* Cuiping Xiao, Qingzhong Li and Jianbo Cheng College of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, China * Corresponding author: E-mail: liwenzuo2004@ 126.com Received: 10-11-2015 Abstract Quantum chemical calculations have been performed for the substitution reactions of the aluminum chlorogermylenoid H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 to get more insights into the reactivity of H2GeClAlCl2. The theoretical calculated results indicated that the substitution reactions of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 proceeded in a concerted manner. There were one transition state and one intermediate which connected the reactants and the products along the potential energy surface. The six substitution reactions of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 are compared with the addition reaction s of H2Ge with these hydrides. And based on the calculated results we concluded that the substitution reactions of H2GeClAlCl2 with these hydrides involve two steps, one is dissociation onto H2Ge with AlCl3, and the other is the addition reactions of H2Ge with HF, H2O, NH3, HCl, H2S, and PH3. 2 3 2 2 3 Keywords: H2GeClAlCl2; substitution reaction; MP2; CCSD 1. Introduction Since many organic germanium compounds have been found to have biologic activity,1-6 the properties and reactions of germylenes and their derivatives have been well studied.7,8 Germylenoid is a kind of important derivative of germylene, and may have the stronger stability than germylene. Similar to carbenoids9,10 and silylenoids,11,12 germylenoids are complexes formed between free germylenes and inorganic salts, which can be expressed as R1R2GeMX (M = alkali metal, X = halogen). In 1991 Lei et al. firstly demonstrated that germylenoid might be the intermediate in the reaction of dichlorodimethylgermane with substituted butadiene.13 Since then several subsequent organic experimental works also indicated the significance of germylenoids as active intermediates.14-19 However, until now no stable germylenoid has been prepared by experiments. Therefore, it is necessary to carry out systemic investigations on germylenoids to investigate their structures, properties, and reactions using theoretical calculations. Many theoretical studies on the structures, properties, and reactions of the germylenoids have been carried out. In 1999, Qiu et al. firstly researched the isomeric structure of the germylenoid H2GeLiF by ab initio calculations.20 Until now, a few kinds of germylenoids have been investigated21-34 Most of these theoretical works mainly focused on the germylenoids containing alkali metals such as Li and Na. In 1970, Glockling et al.35 suggested that germanium-aluminium compounds were high reactivity intermediates in the reaction between bistri-methylgermylmercury and aluminium turnings. A more comprehensive study on aluminium-germanium compounds is of great scientific significance and academic value. Is aluminium-germyloenoid exists? And how is its reactivity? In 2009, we firstly investigated the geometries, energies, and isomerization reactions of aluminum chlorogermylenoid H2GeClAlCl2.31 However, the reactions of H2GeClAlCl2 with other substances have been not researched until now. In order to fill this gap and explore the reactivity of the germylenoid H2GeClAlCl2, in present work we implemented theoretical study on the substitution reactions of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 using ab initio quantum chemical calculations. Through this work, we hope (I) to get the Yan et al.: Substitution Reactions of the Aluminum 272 Acta Chim. Slov. 2016, 63, 271-278 structures and energies of all stationary points, (II) to confirm the thermodynamics of the substitution reactions, (III) to predict their activation barriers, and (IV) to clarify the reaction mechanisms on the substitution reactions of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3. 2. Computational Methods The geometries of all the stationary points presented here were fully optimized at the MP2/6-311+G (d, p) level.36-38 The geometries were first optimized and then the harmonic vibrational frequencies were calculated at the same level of theory to characterize all stationary points as either local minima (no imaginary frequencies) or transition states (one imaginary frequencies). The substitution reaction pathways were examined by IRC (intrinsic reaction coordinate)39 calculations at the same level to verify the reactants and the products to which each TS was connected. In order to improve the treatment of electron correlation the single-point calculations were made at the CCSD (Coupled cluster with singles and doubles)40,41 level using the 6-311++G (d, p) basis set for all species. All of the calculations were carried out using Gaussian 09 series of programs.42 3. Results and Discussions Previous theoretical calculations31 indicated that the aluminum chlorogermylenoid H2GeClAlCl2 has three equilibrium configurations (see Figure 1), the p-complex (a), the three-membered-ring (b), and the "classical" tetra-hedral structure (c), in which the p-complex structure is the lowest in energy and is the most stable structure. Therefore, the p-complex structure was selected as the reac-tant when we researched the substitution reactions of H2GeClAlCl2 and HF, H2O, NH3, HCl, H2S, PH3 in present work. Theoretical calculations indicated the substitution reactions of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 could be described as the following formula: H2GeClAlCl2 + RH ^ H3GeR + AlCl3 (R = F, OH, NH2, Cl, SH, and PH2) Based on the calculated results, we found that along the potential energy surface, there are one transition state (TS) and one intermediate (IM) which connect the reac-tants and the products (P and AlCl3). The geometries of the stationary points calculated at the MP2/6-311+G (d, p) level are shown in Figure 2 and Figure 3, the relative energies of the stationary points are listed in Table 1 and 2, respectively. For the convenience of expression, the trans-fer-H in RH is marked as H1. 3. 1. Substitution Reactions of H2GeClAlCl2 with HF, H2O, and NH3 3. 1. 1. The Structures and Energies of the Transition States As displayed in Figure 2, there is an exposed space that can be attacked by nucleophiles or electrophiles under the Ge atom, and the substitution reactions between H2GeClAlCl2 and HF, H2O, NH3 should occur in this region. From Figure 2 we can see that the three transition states (TS1, TS2, and TS3) have the similar structures. There is a three-membered-ring (X-Ge-H1, X = F, O, N) in each TS. Compared to the isolated reactants HF, H2O, and NH3, the R-H1 bond distances are sharply lengthened by about 0.0423, 0.0467, and 0.0488 nm , where the bond elongations correspond to about 31.6%, 32.7%, and 32.5% of its original length, respectively. Therefore, the migrating H1 atom has a strong reactant-like property. As listed in Table 1, the relative energies of TS1, TS2, and TS3 to their reactants are 159.39, 178.01, and 179.81 k-J/mol, respectively. The frequency analysis calculations were carried out at the MP2/6-311+G (d, p) level. The theoretical results indicated that each TS has only one imaginary frequency, which are 1378.1 i, 1436.1i, and 1433.7i cm-1, respectively. The calculated unique imaginary frequency vibration of TS1, TS2, and TS3 involves bond formation between Ge atom and R group in concert with R-H1 bond breaking, and H1 atom migration to Ge atom. Besides, the \fy Gé- Cl ...y ci -Cl p va H Cl 'Cl a) b) Figure 1. The equilibrium configurations of the germylenoid H2GeClAlCl2, see Ref. 31 Cl \ Cl H -A1 'Cl c) Yan et al.: Substitution Reactions of the Aluminum Acta Chim. Slov. 2016, 63, 271-278 273 Table 1. Relative energies (in kJ/mol) of transition states (TSs), intermediates (IMs), and products of the substitution reactions of H2GeClAlCl2 with R-H (R = F, OH, NH2). (Values in parenthesis were calculated in benzene) Species R = F R = OH R = NH, H2GeClAlCl2 + R-H TS IM GeH3R + AlCl3 0.00 (0.00) 159.39 (165.63) -89.75 (-91.81) -71.92 (-70.70) 0.00 (0.00) 178.01 (188.55) -74.91 (-73.30) -50.64 (-45.28) 0.00 (0.00) 179.81 (189.29) -80.61 (-81.84) -37.90 (-31.12) IRC calculations displayed that the TSs are the real transition states which connect the reactants and the intermediates. 3. 1. 2. The Structures and Energies of the Intermediates and Products After getting over the transition states, the Ge-R and Ge-H1 bonds gradually form with the breakdown of R-H1 bond and the intermediates IMs form. As shown in Figure 2, IM1, IM2, and IM3 are the three intermediates of the three substitution reactions. From Figure 2, we can see that the X-Ge-H1 (X = F, O, N) bond angles of IMs are much larger than those of TSs. For IM1, the F-Ge-H1 bond angle (107.0°) is about 67.0° larger than that of TS1 (40.0°); For IM2, the O-Ge-H1 bond angle (112.3°) is about 68.0° larger than the that of TS2 (44.3°); For IM3, the N-Ge-H1 bond angle (110.3°) is about 62.4° larger than that of TS3 (47.9°). In the IMs, the R-H1 bonds have been broken completely. The Ge-H1 and Ge-X bond lengths of IMs are shorter than those of TSs respectively. For IM1, the Ge-H1 bond CL / /2.07 C1< 2.081 Al CI .078 CL 2.089- kA Al .CI .088 2.074^ /2.073 Al H 2.939/' V.158 „ H 3.022/' \ _ H H3149/ \ \ / \ I / \ 6 H, % I / \2'105 2.084 % ,->45.0 \ H// 2.028 '''A \ H^., 1-983 /\n.9 \ ----1-----------pi O-----i—Ge—L-------ri N-----1—r«>--t------- ue 2.650 u \ 44 3V' 2.912 •426\ >^6,3 H \ 40.1 40\ H1 ■CI "N—---r \ 47-9j .502\ Ge—3-T9-Ct 1.634 TS 1 TS2 TS3 % / 2,076% /2.076 'A I A 1 /"V ,''3.170 \ „ / 1 H 107.0 % \ / 2.079% /2.1 Al / 3.212 \ CI 079 CI 2 HF H IM] /,,2.3 H H, 821 N" I jP X / H A1 I V.098 ^0^959 1/3.202 \ H u Q H Ge' CI H 1.523jjl ¡M2 »•«W IM3 /\"H u \ NH 1.014 [••"H \ H Figure 2. The geometries of the stationary points [reactants, transition states (TSs), intermediates (IMs), and products (Ps)] of the substitution reactions of the germylenoid H2GeClAlCl2 with HF, H2O, and NH3 in gas phase calculated at MP2/6-311+G (d, p) level (Bond lengths are given in A and angles in degrees) Yan et al.: Substitution Reactions of the Aluminum 274 Acta Chim. Slov. 2016, 63, 271-278 length (0.1515 nm) and the Ge-F bond length (0.1780 nm) is about 0.0092 nm and 0.0304 nm shorter than those of TS1 respectively; For IM2, the Ge-H1 bond length (0.1523 nm) and the Ge-O bond length (0.1791 nm) is about 0.0090 nm and 0.0237 nm shorter than those of TS2 respectively; For IM3, the Ge-H1 (0.1519 nm) and Ge-N bond length (0.1821 nm) is about 0.0115 nm and 0.0162 nm shorter than the Ge-H1 (0.1634 nm) and Ge-N bond length (0.1983 nm) of TS3, respectively. As listed in Table 1, the relative energies of IM1, IM2, and IM3 to their reactants are -89.75, -74.91, and -80.61 kJ/mol, respectively. The MP2/6-311+G (d, p) calculations indicated that the IMs could further dissociate to H3GeR and AlCl3, which are the products of the substitution reactions of H2GeClAlCl2 and RH (R = F, OH, and NH2). The dissociations of IMs are monotonously energy increasing process. As shown in Figure 2, the three H3GeR (denote as P1, P2, and P3) are the substituted germane. As listed in Table 1, the relative energies of the products (H3GeR + AlCl3) of the three substitution reactions to their reactants are -71.92, -50.64, and -37.90 kJ/mol when R = F, OH, and NH2, respectively. Therefore, the three substitution reactions are all exothermic. 3. 2. Substitution Reactions of H2GeClAlCl2 with HCl, H2S, and PH3 3. 2. 1. The Structures and Energies of the Transition States As displayed in Figure 3, three transition states (TS4, TS5, and TS6) have the similar structures. There is a three-membered-ring (X-Ge-H1, X = Cl, S, P) in each TS. Compared to the isolated reactants HCl, H2S, and PH3, the R-H1 bond distances are sharply lengthened by about 0.417, 0.480, and 0.0279 nm, where the bond elongations correspond to about 32.8%, 36.0%, and 19.8% of its original length, respectively. Therefore, the migrating H1 atom has a strong reactant-like property. As listed in Table 2, the relative energies of TS4, TS5, and TS6 to their reactants are 112.61, 120.36, and 179.66 kJ/mol, respectively. Figure 3. The geometries of the stationary points [reactants, transition states (TSs), intermediates (IMs), and products (Ps)] of the substitution reactions of the germylenoid H2GeClAlCl2 with HCl, H2S, and PH3 in gas phase calculated at MP2/6-311+G (d, p) level (Bond lengths are given in A and angles in degrees) Yan et al.: Substitution Reactions of the Aluminum Acta Chim. Slov. 2016, 63, 271-278_ 275 Table 2. Relative energies (in kJ/mol) of transition states (TSs), intermediates (IMs), and products of the substitution reactions of H2GeClAlCl2 with R-H (R = Cl, SH, PH2). (Values in parenthesis were calculated in benzene) Species R = Cl R = SH R = PH 2 H2GeClAlCl2 + R-H 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) TS 112.61 (114.20) 120.36 (122.05) 179.66 (179.22) IM -123.18 (-130.23) -101.82 (-107.91) -95.75 (-102.38) GeH3R + AlCl3 -102.84 (-106.66) -77.91 (-80.10) -58.17 (-58.52) The frequency analysis calculations were carried out at the MP2/6-311+G (d, p) level. The theoretical results indicated that each TS has unique imaginary frequency, which are 1053.1i, 974.2i, and 913.6i cm-1, respectively. The calculated imaginary frequency vibration of TS4, TS5, and TS6 involves bond formation between Ge atom and R group in concert with R-H1 bond breaking, and H1 atom migration to Ge atom. Besides, the IRC calculations displayed that the TSs are the real transition states which connect the reactants and the intermediates. 3. 2. 2. The Structures and Energies of the Intermediates and Products As shown in Figure 3, IM4, IM5, and IM6 are the three intermediates of the three substitution reactions. From Figure 3, we can see that the X-Ge-H1 (X = Cl, S, P) bond angles of IMs are much larger than those of TSs. For IM4, the Cl-Ge-H1 bond angle (109.5°) is about 68.6° larger than that of TS4 (40.9°); For IM5, the S-Ge-H1 bond angle (113.3°) is about 67.1° larger than the that of TS5 (46.2°); For IM6, the P-Ge-H1 bond angle (112.5°) is about 65.9° larger than that of TS6 (46.6°). In the IMs, the R-H1 bonds have been broken completely. The Ge-H1 and Ge-X bond lengths of IMs are shorter than those of TSs respectively. For IM4, the Ge-H1 bond length (0.1517 nm) and the Ge-Cl bond length (0.2143 nm) is about 0.0099 nm and 0.0395 nm shorter than those of TS4 respectively; For IM5, the Ge-H1 bond length (0.1523 nm) and the Ge-S bond length (0.2219 nm) is about 0.0079 nm and 0.0286 nm shorter than those of TS5 respectively; For IM6, the Ge-H1 (0.1528 nm) is about 0.0273 nm shorter than that of TS6 (0.1801 nm), however, the Ge-P bond length (0.2309 nm) is slightly lengthened by about 0.0007 nm. As listed in Table 2, the relative energies of IM4, IM5, and IM6 to their reactants are -123.18, -101.82, and -95.75 kJ/mol, respectively. The IMs could further dissociate to H3GeR (R = Cl, SH, and PH2) and AlCl3, which are the products of the substitution reactions of H2GeClAlCl2 and HCl, H2S, and PH3. The dissociations of IMs are monotonously energy increasing process. As shown in Figure 3, the three H3Ge-R (denote as P4, P5, and P6) are the substituted germane. As listed in Table 2, the relative energies of the products (H3GeR + AlCl3) of the three substitution reactions to their reactants are -102.84, -77.91, and -58.17 kJ/mol when R = Cl, SH, and PH2, respectively. Therefore, the three substitution reactions are all exothermic. Our theoretical results indicated that the reaction mechanism of H2GeClAlCl2 with HCl, H2S, and PH3 is similar to that of H2GeClAlCl2 with HF, H2O, and NH3. 3. 3. The Mechanisms of the Substitution Reactions In order to fully confirm the substitution reactions path, the IRC computations are carried out at the MP2/6-311+G (d, p) level. Here the reaction of H2GeClAlCl2 with HF is chosen to be an example. IRC calculations have been performed on the basis of the calculated TS1 to investigate the interaction between H2GeClAlCl2 and HF in this substitution process. And the total energy changes and the variations of Ge-F, F-H1, and Ge-H1 bond distances along the reaction coordinates for the substitution reaction of H2GeClAlCl2 with HF are shown in Figure 4. From Figure 4 we can find that the reaction coordinate passes from point -9.0 to 0.0, the total energy increases sharply and reaches its maximum at point 0.0. In this region, the lengths of Ge-F and Ge-H1 bond decrease obviously. After the maximum point, the total energy decreases sharply and the lengths of F-H1 bond increase obviously. The charge distributions of the atoms in the stationary points can reflect the mechanism of the reaction. We calculate the natural charge distributions of the atoms in reactants, TSs, IMs, and products at the MP2/6-311+G (d, p) level. For TSs, the X (X = F, O, N, Cl, S, P) atom and H1 atom have more negative charge than those in reactants and the Ge atom has more positive charge than that in reactants; For IMs, the H1 atom has more negative charge and the Ge atom has more positive charge than those in TSs, respectively. The change of the charge distributions also implies the fracturing of the R-H1 bond and the forming of the Ge-H1 and Ge-R bonds. Taking the reaction of H2GeClAlCl2 with HF as an example, in TS1, the positive charge of H1 atom (0.291 e) is less than that in HF (0.557 e), the negative charge of F atom (-0.731 e) is more than that in HF (-0.557 e), and the positive charge of Ge atom (0.954 e) is more than that in H2GeClAlCl2 (0.723 e). The changes of the charge distributions imply the fracturing of the F-H1 bond and the forming of the Ge-H1 and Ge-F bonds. In IM1, the charge of H1 atom Yan et al.: Substitution Reactions of the Aluminum 276 Acta Chim. Slov. 2016, 63, 271-278 -3801.96 -3801.9 -3802.00 ■ 3 -3802.02-rf tei -3802.04 ■ -3802.06 -10 -5 1 1 1 1 1 E \ / H-OH > H-NH2 for the first-row hydrides and H-Cl > H-SH > H-PH2 for the second-row. This point is consistent with the calculated natural charges on the H1 atoms of the RH, where the natural charges on the H1 atoms are 0.557, 0.457, 0.342 e in F-H1, OH-H1, NH2-H1 for the first-row hydrides and 0.247, 0.111, -0.050 e in Cl-H1, SH-H1, PH2-H1 for the second-row. On the other hand, the reaction barriers are lower for the second-raw hydride and reactions are more exothermic than the first-raw hydride, which means the substitution reactions of the second-row hydrides proceed more easily than those of the first-row. And this point is consistent with the strength of R-H bonds, where the common bond energies for H-Cl, H-S, and H-P (428, 363, and 322 k-J/mol)43 are lower than that for the corresponding H-F, H-O, and H-N (565, 459, and 386 kJ/mol),43 respectively. 3. 5. The Comparisons of the Reactions of H2Ge + RH and H2GeClAla2 + RH We also calculated the reactions of H2Ge with HF, H2O, NH3, HCl, H2S, and PH3 at the same level of theory. The calculated results indicated that the reaction pathway of the reactions of H2Ge with these hydrides is different from that of H2GeClAlCl2 with them. On the pathway of the reactions of H2Ge with HF, H2O, NH3, HCl, H2S, and PH3, there is only one transition state which connected the reactants and the products. For the reactions of H2Ge with these hydrides, the CCSD/6-311++G (d, p)//MP2/6-311+G (d, p) calculated reaction barriers are 101.72 (HF), 116.88 (H2O), 125.57 (NH3), 49.50 (HCl), 52.37 (H2S), and 129.59 (PH3), respectively. Therefore, the reactions of H2Ge with these hydrides are easier to occur than the substitution reactions of H2GeClAlCl2 with these hydrides. On the other hand, for the H2GeClAlCl2, the dissociation energy onto H2Ge and AlCl3 is about 96.11 kJ/mol. Thus, the possible reaction pathway of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 seems to firstly dissociation onto H2Ge and Al-Cl3, and then the addition of H2Ge with HF, H2O, NH3, HCl, H2S, and PH3 occurs. Yan et al.: Substitution Reactions of the Aluminum Acta Chim. Slov. 2016, 63, 271-278 277 4. Conclusions In present work, the substitution reactions of the aluminum chlorogermylenoid H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 have been studied using MP2 and CCSD methods. It should be mentioned that this work has provided the first theoretical demonstration about the reaction trajectory and theoretical estimation of the activation energy and reaction energy for those processes. The theoretical results indicate that the mechanisms of the six reactions are identical to each other. For each substitution reaction a transition state and an intermediate were located. The calculated barrier heights for the six different substitution reactions of R = F, OH, NH2, Cl, SH, and PH2 are 159.39, 178.01, 179.81, 112.61, 122.05, and 179.66 kJ/mol, respectively. All the substitution reactions are exothermic. These theoretical calculations suggest that: (i) the mechanisms of the six reactions are identical; (ii) under the same condition the substitution reactions should occur easily in the order of H-F > H-OH > H-NH2 for the first-row hydrides and H-Cl > H-SH > H-PH2 for the second-row; (iii) the substitution reactions of the second-row hydrides proceed more easily than those of the first-row. For the H2GeClAlCl2, the dissociation energy onto H2Ge and AlCl3 is about 96.11 kJ/mol. And the reactions of H2Ge with HI3, H2O, NH3, HCl, H2S, and PH3 have lower energy barriers than those of H2GeClAlCl2 with these hydrides. Therefore, the substitu-tio2n reaction2s of H2GeClAlCl2 with HF, H2O, NH3, HCl, H2S, and PH3 involve two steps. One is dissociation onto H2Ge and AlCl3, and the other is the addition reactions of H2Ge with HF, H2O, NH3, HCl, H2S, and PH3. 5. Acknowledgements This work was supported by the National Natural Science Foundation Committee of China (No. 21103145), the Fund for Youth of Yantai University (No. HY13Z03), and the Special Foundation of Youth Academic Backbone of Yantai University. Professor Cheng acknowledges support by the Open fund (sklssm201418) of the State Key Laboratory of Supramolecular Structure and Materials, Ji-lin University. B.-F. Yan acknowledges the Graduate Innovation Foundation of Yantai University, GIFYTU. 6. References 1. J. Satge, Pure Appl. Chem. 1984, 56, 137-150. http://dx.doi.org/10.1351/pac198456010137 2. S. Shoda, S. Iwata, K. Yajuma, K. Yagi, Y. Ohnishi, S. Koba-yashi, Tetrahedron 1997, 532, 15281-15295. http://dx.doi.org/10.1016/S0040-4020(97)00963-0 3. M. Rivière-Baudet, M. Dahrouch, H. Gornitzka, J. Organo-met. Chem. 2000, 595, 153-157. http://dx.doi.org/10.1016/S0022-328X(99)00577-X 4. E. Broclawik, A. Bocho-Janiszewska, J. Mol. Struct. (Theoc-hem.) 2000, 531, 241-247. http://dx.doi.org/10.1016/S0166-1280(00)00446-2 5. M. K. Khosa, M. Mazhzr, S. Ali, K. C. Molloy, S. Dastgir, F. Shaheen, Turk. J. Chem. 2006, 30, 731-743. 6. M. Z. Kassaee, M. Ghambarian, S. M. Musavi, J. Organo-met. Chem. 2005, 690, 4692-4703. http://dx.doi.org/10.1016/jjorganchem.2005.07.086 7. W. P. Neumann, Chem. Rev. 1991, 91, 311-334. http://dx.doi.org/10.1021/cr00003a002 8. V. N. Khrustalev, I. V. Glukhov, I. V. Borisova, N. N. Zeml-yansky, Appl. Organometal. Chem. 2007, 21, 551-556. http://dx.doi.org/10.1002/aoc.1252 9. G. Boche, J. C. W. Lohrenz, Chem. Rev. 2001,101, 697-756. http://dx.doi.org/10.1021/cr940260x 10. V. Capriati, S. Florio, Chem. Eur. J. 2010, 16, 4152-4162. http://dx.doi.org/10.1002/chem.200902870 11. M. Flock, C. Marschner, Chem. Eur. J. 2005, 11, 4635-4642. http://dx.doi.org/10.1002/chem.200401353 12. G. Molev, D. Bravo-Zhivotoskii, M. Karni, B. Tumanskii, M. Botoshansky, Y. Apeloig, J. Am. Chem. Soc. 2006, 128, 2784-2785. http://dx.doi.org/10.1021/ja0575880 13. D. Q. Lei, and P. P. Gaspar, Polyhefron 1991, 10, 1221-1225. http://dx.doi.org/10.1016/S0277-5387(00)86098-2 14. T. Ohtaki, W. Ando, Organometallics 1996, 15, 3103-3105. http://dx.doi.org/10.1021/om9600147 15. M. Ichinohe, H. Sekiyama, N. Fukaya, A. Sekiguchi, J. Am. Chem. Soc. 2000, 122, 6781-6782. http://dx.doi.org/10.1021/ja000057l 16. A. Sekiguchi, V. Y. Lee, Chem. Rev. 2003, 103, 1429-1448. http://dx.doi.org/10.1021/cr0100300 17. T. Sasamori, N. Tokitoh, Organometallics 2006, 25, 35223532. http://dx.doi.org/10.1021/om060158d 18. T. Tajima, T. Sasamori, N. Takeda, N. Tokitoh, K. Yoshida, M. Nakahara, Organometallics 2006, 25, 230-235. http://dx.doi.org/10.1021/om0507629 19. A. C. Filippou, K. W. Stumpf, O. Chernov, G. Schnakenburg, Organometallics 2012, 31, 748-755. http://dx.doi.org/10.1021/om201176n 20. H. Y. Qiu, W. Y. Ma, G. B. Li, C. H. Deng, Chin. Chem. Lett. 1999, 10, 511-514. 21. X. J. Tan, P. Li, D. S. Wang, X. L. Yang, J. Mol. Struct. (Theochem.) 2006, 761, 27-30. http://dx.doi.Org/10.1016/j.theochem.2005.12.013 22. X. J. Tan, P. Li, X. Yang, D. S. Wang, Int. J. Quan. Chem. 2006, 106, 1902-1906. http://dx.doi.org/10.1002/qua.20961 23. W. Y. Ma, Y. F. Zhu, J. H. Zhou, Y. Z. Fang, J. Mol. Struct. (Theochem.) 2007, 817, 77-81. http://dx.doi.org/10.1016Zj.theochem.2007.04.023 24. Y. F. Zhu, Y. Z. Fang, J. H. Zhou, W. Y. Ma, Chin. J. Struct. Chem. 2007, 26, 395-400. 25. W. Z. Li, H. N. Tan, C. P. Xiao, B. A. Gong, J. B. Cheng, Acta Phys. Chim. Sin. 2007, 23, 1811-1814. 26. W. Z. Li, J. B. Cheng, B. A. Gong, C. P. Xiao, J. Organomet. Chem. 2006, 691, 5984-5987. http://dx.doi.org/10.1016/jjorganchem.2006.09.028 Yan et al.: Substitution Reactions of the Aluminum 278 Acta Chim. Slov. 2016, 63, 271-278 27. W. Z. Li, F. X. Yang, J. B. Cheng, Q. Z. Li, B. A. Gong, Chin. J. Struct. Chem. 2012, 31, 19-26. 28. X. J. Tan, W. H. Wang, P. Li, Q. F. Wang, G. X. Zheng, F. Liu, J. Organomet. Chem. 2008, 693, 475-482. http://dx.doi.Org/10.1016/j.jorganchem.2007.11.019 29. W. Z. Li, B. A. Gong, J. B. Cheng, C. P. Xiao, J. Mol. Struct. (Theochem.) 2007, 847, 75-78. http://dx.doi.org/10.1016Zj.theochem.2007.08.036 30. W. Z. Li, J. B. Cheng, Q. Z. Li, B. A. Gong, J. Z. Sun, Acta Phys. Chim. Sin. 2009, 25, 121-125. 31. W. Z. Li, J. B. Cheng, Q. Z. Li, B. A. Gong, J. Z. Sun, J. Organomet. Chem. 2009, 694, 2898-2901. http://dx.doi.org/10.1016/jjorganchem.2009.04.023 32. W. Z. Li, Q. Z. Cao, Y. W. Pei, R. Li, H. J. Zhu, Q. Z. Li, J. B. Cheng, Struct. Chem. 2012, 23, 867-871. http://dx.doi.org/10.1007/s11224-011-9933-6 33. C. P. Xiao, W. Z. Li, Q. Z. Li, J. B. Cheng, Russ. J. Phys. Chem. A 2014, 88, 1097-1102. http://dx.doi.org/10.1134/S0036024414070103 34. W. Z. Li, J. B. Cheng, B. A. Gong, C. P. Xiao, Chin. J. Struct. Chem. 2007, 26, 613-617. 35. F. Glockling, J. R. C. Light, R. G. Strafford, J. Chem Soc. A 1970, 426-432. http://dx.doi.org/10.1039/j19700000426 36. S. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200-1211. http://dx.doi.org/10.1139/p80-159 37. L. A. Curtis, K. Raghavachari, J. A. Pople, J. Chem. Phys. 1993, 98, 1293-1298. http://dx.doi.org/10.1063/L464297 38. R. O. Pop, M. Ilici, M. Andoni, V. N. Bercean, C. Muntean, M. M. Venter, I. Julean, Acta Chim. Slov. 2015, 62, 8-14. 39. C. Gonzales, H. B. Schlegel, J. Chem. Phys. 1991, 95, 5853-5860. http://dx.doi.org/10.1063/L461606 40. K. A. Peterson, J. Chem. Phys. 2003, 119, 11099-11112. http://dx.doi.org/10.1063/L1622923 41. K. A Peterson, D. Figgen, E. Goll, H. Stoll, M. Dolg, J. Chem. Phys. 2003, 119, 11113-11123. http://dx.doi.org/10.1063/L1622924 42. M. J. Frisch, G. W. Trucks, H. B. Schlegel, et al., Gaussian 09, Revision A.02, Gaussian Inc., Wallingford CT, 2009. 43. http://www.wiredchemist.com/chemistry/data/bond_ener-gies_lengths.html. Povzetek Da bi pridobili več vpogleda v reaktivnost aluminijevega klorogermilenoida H2GeClAlCl2 smo izvedli kvantokemijske izračune za reakcije substitucije z HF, H2O, NH3, HCl, H2S, in PH3. Ugotovili smo, da vse proučevane reakcije potekajo podobno-preko enega prehodnega stanje in enega intermediata. Reakcije substitucije H2GeClAlCl2 z HF, H2O, NH3, HCl, H2S, in PH3 smo primerjali tudi z dodatnimi reakcijami H2Ge s temi hidridi. Izkazalo se je, da reakcije substitucije H2GeClAlCl2 s hidridi potekajo v dveh stopnjah, ena je disociacija v H2Ge in AlCl3 in drugo predstavljajo dodatne reakcije H2Ge z HF, H2O, NH3, HCl, H2S, in PH3. Yan et al.: Substitution Reactions of the Aluminum DOI: 10.17344/acsi.2015.2125 Acta Chim. Slov. 2016, 63, 279-286 279 Scientific paper Synthesis, Characterization and X-Ray Crystal Structures of cis--Dioxomolybdenum(VI) Complexes of Similar Tridentate Aroylhydrazone Schiff Bases with Catalytic Epoxidation Activity Qing Liu,1 Jiahui Lin,1 Juan Liu,1 Wu Chen1'2 and Yongming Cui3* 1 School of Textile Science and Engineering, Wuhan Textile University, Wuhan 430073, P. R. China 2 Ministry of Education Key Laboratory for Textile Fibers and Products, Wuhan Textile University, Wuhan 430073, P. R. China 3 School of Environmental Engineering, Wuhan Textile University, Wuhan 430073, P. R. China * Corresponding author: E-mail: cym981248@sohu.com Received: 14-11-2015 Abstract Two new ds-dioxomolybdenum(VI) complexes with general formula [MoO2L(MeOH)], where L = L1 = W-(3,5-dibromo-2-hydroxybenzylidene)-4-trifluoromethylbenzohydrazide for complex 1, and L = L2 = W-(3-bromo-5-chloro-2-hydroxy-benzylidene)-4-trifluoromethylbenzohydrazide for complex 2, have been synthesized and fully characterized on the basis of elemental analysis, FT-IR, molar conductivity, and electronic spectra. The complexes are also characterized by single crystal X-ray diffraction. The complexes have distorted octahedral structures in which the aroylhydrazones behave as dia-nionic ligands. It is also revealed from the crystal structures that the Mo(VI) center adopts NO5 donor environment, and the octahedral coordination is furnished by two oxido groups and oxygen atoms of neutral methanol molecules. The catalytic properties were investigated for epoxidation of cyclooctene using aqueous tert-butyl hydroperoxide as the oxidant. Keywords: Dioxomolybdenum(VI); Aroylhydrazone; Schiff base; X-ray crystal structure; Catalytic epoxidation activity 1. Introduction In the last 60 years, Schiff base ligands and their transition metal complexes have attracted considerable attention, not only for their facile synthesis, but also for potential biological, catalytic and industrial applications.1 In recent years, vanadium complexes with hydrazones have been widely studied, either from the structural or catalytic aspect.2 As we know, catalytic epoxidation of olefins is an important reaction in organic synthesis. Many transition metal complexes are active catalysts for this process.3 Yet, among the complexes, molybdenum complexes have a unique place in coordination chemistry and have displayed very high catalytic activities in the oxidation of ole-fins and sulfides.4 In the present work, two similar aroylhydrazone Schiff bases, N'-(3,5-dibromo-2-hydroxybenzylidene)-4-trifluoromethylbenzohydrazide (H2L1) and N'-(3-bromo-5-chloro-2-hydroxybenzylide-ne)-4-trifluoromethylbenzohydrazide (H2L2), were prepa- red and used to prepare dioxomolybdemum(VI) complexes with [MoO2(acac)2] in methanol. The catalytic properties were investigated for epoxidation of cyclooctene using aqueous tert-butyl hydroperoxide as the oxidant. 2. Experimental 2. 1. Materials and Methods 4-Trifluoromethylbenzohydrazide was prepared as described in the literature.5 3,5-Dibromosalicylaldehyde and 3-bromo-5-chlorosalicylaldehyde were purchased from Alfa Aesar and used as received. [MoO2(acac)2] was prepared as described in the literature.6 Reagent grade solvents were used as received. Microanalyses of the complexes were performed with a Vario EL III CHNOS elemental analyzer. Infrared spectra were recorded as KBr pellets with an FTS-40 spectrophotometer. Electronic spectra were recorded on a Lambda 900 spectrometer. The Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures 280 Acta Chim. Slov. 2016, 63, 279-286 catalytic reactions were followed by gas chromatography on an Agilent 6890A chromatograph equipped with an FID detector and a DB5-MS capillary column (30 m x 0.32 mm, 0.25 pm). Molar conductance measurements were made by means of a Metrohm 712 conductometer in acetonitrile. 1H NMR spectra were recorded on a Bruker spectrometer at 300 MHz. 2. 2. Synthesis of the Aroylhydrazone Schiff Bases The aroylhydrazone Schiff bases H2L1 and H2L2 were synthesized in a similar way by refluxing a methanolic solution (30 mL) of 4-trifluoromethylbenzohydrazide (10 mmol, 2.04 g) with 3,5-dibromosalicylaldehyde (10 mmol, 2.80 g) and 3-bromo-5-chlorosalicylaldehyde (10 mmol, 2.35 g), respectively. Reflux was continued for 1 h in oil bath during which a solid compound separated. It was filtered and washed with cold methanol. The crude product was recrystalli-zed from methanol and dried over anhydrous CaCl2. H2L1: Yield: 3.73 g (80%). IR data (KBr pellet, cm 1): 3351 v(O-H), 3218 v(N-H), 1653 v(C=O), 1615 v(C=N). UV-Vis data in methanol (nm): 283, 362, 425. Analysis: Found: C 38.50, H 2.02, N 5.93%. Calculated for C15H9Br2F3N2O2: C 38.66, H 1.95, N 6.01%. 1H NMR (300 MHz, ¿f-DMSO): ¿12.13 (s, 1H, OH), 11.22 (s, 1H, NH), 8.71 (s, 1H, CH=N), 7.92 (d, 2H, ArH), 7.72-7.85 (m, 4H, ArH). H2L2: Yield: 3.85 g (91%). IR data (KBr pellet, cm-1): 33347 v(O-H), 3227 v(N-H), 1655 v(C=O), 1617 v(C=N). UV-Vis data in methanol (nm): 281, 360, 425. Analysis: Found: C 42.91, H 2.23, N 6.55%. Calculated for C15H9BrClF3N2O2: C 42.73, H 2.15, N 6.64%. 1H NMR (5300 MHz, d6-DMSO): 8 12.37 (s, 1H, OH), 11.15 (s, 1H, NH), 8.72 (s, 1H, CH=N), 7.92 (d, 2H, ArH), 7.83 (d, 2H, ArH), 7.49-7.56 (m, 2H, ArH). 2. 3. Preparation of the Complexes The complexes [MoO2L1(MeOH)] (1) and [Mo-O2L2(MeOH)] (2) were prepared in a similar way by refluxing a methanolic solution (30 ml) of [MoO2(acac)2] (1.0 mmol, 0.33 g) with methanolic solutions of H2L1 (1.0 mmol, 0.47 g) and H2L2 (1.0 mmol, 0.42 g), respectively. Initially on mixing the two components immediately an orange yellow color was observed. The mixture was reflu-xed for 1 h. Orange crystals were formed during slow evaporation of the reaction mixture. The resulting orange crystals were filtered, washed with cold methanol and dried over anhydrous CaCl2. [MoO2L1(MeOH)] (1): Yield: 0.40 g (69%). IR data (KBr pellet, cm-1): 3461 v(O-H), 1606 v(C=N), 1326 K^phenolateX 1135 KN~NX 948 V^riS-lUcO,). 852 vasym(ds-MoO2). UV-Vis data in acetonitrile (nm): 293, 305, 335, 407. Molar conductance (10-3 M, acetonitrile): 25 Q-1 ■ cm2 ■ mol-1. Analysis: Found: C 33.32, H 2.03, N 4.75%. Calculated for C16H11BrClF3MoN2O5: C 33.16, H 1.91, N 4.83%. 1H NMR (300 MHz, d6-DMSO): 8 10.56 (s, 1H, OH), 8.37 (s, 1H, CH=N), 8.11 (d, 2H, ArH), 7.637.85 (m, 4H, ArH), 3.35 (s, 3H, CH3). [MoO2L2(MeOH)] (2): Yield: 0.35 g (56%). IR data (KBr pellet, cm-1): 3450 v(O-H), 1605 v(C=N), 1324 Table 1. Crystallographic Data for the Complexes 1 2 Empirical formula C16H11Br2F3MoNA C16H11BrClF3MoN2O5 Formula weight 624.03 57169.5171 3 2 5 Crystal system monoclinic monoclinic Space group P21/c P21/c a [A] 14.9598(10) 14.8713(9) b [A] 7.7777(5) 7.7280(6) c [A] 17.2464(10) 17.2061(11) 92.323(2) 93.017(2) V [A3] 2005.0(2) 1974.7(2) Z 4 4 Pcalcd. [g cm-3] 2.067 1.949 ^ [mm 4.698 2.881 F(000) 1200 1128 Measured reflections 11309 10411 Independent reflections 3724 3671 Observed reflections (I > 2o(I)) 2529 2608 Parameters 265 266 Data completeness 1.023 1.017 Final R indices [I > 2o(I)] 0.0444, 0.0905 0.0406, 0.0936 R indices (all data) 0.0790, 0.1057 0.0669, 0.1043 Goodness-of-fit on F2 1.023 1.017 Largest difference in peak and hole (e A-3) 0.810 and -0.894 0.751 and -0.757 Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures ... Acta Chim. Slov. 2016, 63, 279-286 281 v(C-OphenoIate), 1132 v(N-N), 947 vsym(Ci.-MoO2), 853 vasym(cis-MoO2). UV-Vis data in acetonitrile (nm): 293, 304, 325, 409. Molar conductance (10-3 M, acetonitrile): 23 Q-1 ■ cm2 ■ moI-1. Analysis: Found: C 30.67, H 1.85, N 4.56%. Calculated for C16H11Br2F3MoN2O5: C 30.80, H 1.78, N 4.49%. 1H NMR 6300 MHz, d^-DMSO): 8 10.47 (s, 1H, OH), 8.37 (s, 1H, CH=N), 8.11 (d, 2H, ArH), 7.69 (d, 2H, ArH), 7.50 (s, 1H, ArH), 7.56 (s, 1H, ArH), 3.35 (s, 3H, CH3). 2. 4. Crystal Structure Determination Data were collected on a Bruker SMART 1000 CCD area diffractometer using a graphite monochromator Mo Ka radiation (k = 0.71073 A) at 298(2) K. The data were corrected with SADABS programs and refined on F2 with Siemens SHELXL software.7 The structures were solved by direct methods and difference Fourier syntheses. AII non-hydrogen atoms were refined anisotropicaIIy. The methanoI hydrogen atoms were Iocated from difference Fourier maps and refined isotropicaIIy, with O-H distances restrained to 0.85(1) A. The remaining hydrogen atoms were pIaced in caIcuIated positions and incIuded in the Iast cycIes of refinement. CrystaI data and detaiIs of the data collection and refinement are listed in Table 1. Selected coordinate bond Iengths and angIes are Iisted in TabIe 2. 2. 5. Catalytic Epoxidation Process A mixture of cyclooctene (2.76 mL, 20 mmol), ace-tophenone (internal reference) and the complexes as catalysts (0.05 mmol) was stirred and heated up to 80 °C before addition of aqueous ieri-butyl hydroperoxide (TBHP; 70% w/w, 5.48 mL, 40 mmol). The mixture is initially an emuIsion, but two phases become cIearIy visibIe as the reaction progresses, a coIorIess aqueous one and a yeIIo-wish organic one. The reaction was monitored for 5 h with Table 2. Selected Bond Lengths (A) and Angles (°) for the Complexes 1 2 Mo1-O1 1.930(4) 1.923(3) Mo1-O2 2.004(4) 2.002(3) Mo1-O3 1.680(4) 1.681(4) Mo1-O4 2.321(4) 2.318(3) Mo1-O5 1.699(3) 1.688(3) Mo1-N1 2.262(4) 2.257(3) O3-Mo1-O5 105.6(2) 105.66(16) O3-Mo1-O1 98.6(2) 98.97(18) O5-Mo1-O1 103.24(18) 103.11(14) O3-Mo1-O2 95.9(2) 96.00(17) O5-Mo1-O2 98.37(17) 98.08(13) O1-Mo1-O2 149.54(15) 149.57(12) O3-Mo1-N1 94.44(17) 94.44(14) O5-Mo1-N1 158.47(17) 158.32(14) O1-Mo1-N1 80.88(15) 81.18(12) O2-Mo1-N1 71.39(15) 71.34(11) O3-Mo1-O4 169.59(15) 169.78(13) O5-Mo1-O4 84.13(16) 83.86(13) O1-Mo1-O4 82.32(16) 82.10(13) O2-Mo1-O4 78.80(15) 78.70(12) N1-Mo1-O4 75.42(13) 75.63(11) withdrawaI and anaIysis of organic phase aIiquots (0.1 mL) at required times. Each withdrawn sample was mixed with 2 mL of diethyIether, treated with a smaII quantity of MnO2 and then filtered through silica and analyzed by GC. 3. Results and Discussion 3. 1. Synthesis The aroyIhydrazone Schiff bases and their compIe-xes were synthesized in a faciIe and anaIogous way (Scheme 1). Scheme 1. The synthesis of the aroyIhydrazone Schiff bases and the compIexes Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures 282 Acta Chim. Slov. 2016, 63, 279-286 The aroylhydrazone Schiff bases act as tridentate dianionic ONO donor ligands toward the MoO22+ core. Both Mo(VI) complexes were obtained from a refluxing mixture of the respective ligand and [MoO2(acac)2] in 1:1 molar proportion in methanol. Complexes of the general formula [MoO2L(MeOH)] were isolated as orange single crystals from the reaction mixture by slow evaporation at room temperature. The complexes are stable at room temperature and are found to be fairly soluble in most of the common organic solvents such as methanol, ethanol, ace-tonitrile, DMF and DMSO. The low molar solution conductance of the complexes in acetonitrile, indicates the complexes have non-electrolyte behavior. 3. 2. IR and Electronic Spectra IR spectra of the aroylhydrazone Schiff bases show bands at about 3220 cm-1 for v(N-H), 3350 cm-1 for v(O-H), and 1654 cm-1 for v(C=O).8 The peaks attributed to v(N-H) and v(C=O) are absent in the spectra of the complexes as each ligand binds in dianionic form resulting in losing proton from carbohydrazide group. Strong bands observed at 1606 cm-1 for 1 and 1605 cm-1 for 2 are attributed to v(C=N), which are located at lower frequencies as compared to the free aroylhydrazone Schiff bases, viz. 1615 cm-1 for H2L1 and 1617 cm-1 for H2L2.9 The two molybdenum complexes exhibit two characteristic bands at 948 cm-1 and 852 cm-1 for asymmetric and symmetric stretching of cis-MoO22+ core, respectively.10 Due to IR data, it is obvious that ligands exist in the uncoordinated form in keto-amino tautomer form and in the complexes in imino-enol tautomeric form. This is not uncommon in the coordination of aroylhydrazone Schiff bases.11 Electronic spectra of the complexes recorded in ace-tonitrile solution display strong and medium absorption bands centered at 408 and 293 nm. These peaks are assigned as charge transfer transitions of the type N(pn)-Mo(dn) and O(pn)-Mo(dn), respectively,9 as the ligand based orbitals are either N or O donor types. The slight change of Amax values within each set of peaks may be due to the difference of electron donating capacity of the ligands. 3. 3. Description of Structures The perspective view of complexes 1 and 2 together with the atom numbering scheme are shown in Figures 1 and 2, respectively. The coordination geometry around the molybdenum(VI) atom in the complexes reveals a distorted octahedral environment with NO5 chromophore. The aroylhydrazone Schiff base behaves as dianionic tridenta-te ligand binding through the phenolate oxygen, the eno-late oxygen and the imine nitrogen, and occupies three positions in the equatorial plane. One oxo group is located trans to the imine nitrogen in the equatorial plane. The other oxo group and the methanol oxygen are located at the axial positions. The two terminal oxo groups are hence cis to each other and exhibit typical Mo=O double bond distances.12 The chelate rings are fused along Mo1-N1 bonds. The molybdenum is found to be deviated from the mean equatorial plane defined by the four donor atoms by 0.311(1)  for 1 and 0.314(1)  for 2. The Mo-Omethanol bond lengths in the complexes are longer than the normal single bond lengths (2.31-2.33  against 1.9-2.0 Â). This shows that the methanol molecule is loosely attached to the Mo(VI) center.10b The remaining Mo-O bond lengths are similar to other molybdenum(VI) complexes.13 The bond between Mo and the azomethine nitrogen in complexes 1 and 2 are 2.262(4)  and 2.257(3) Â, respectively, which is comparatively longer than the normal Mo-N single bonds. This is due to the trans effect generated by the oxo group trans to the Mo-N bond.9b The C(8)-O(2) bond lengths in the complexes are 1.30-1.32 Â, which correspond to single bond length of the CAr-OH type. However, the shorter length compared to C-O single bond may be attributed to extended electron delocalization in the li-gands.9b Similarly shortening of C(8)-N(2) bond length (1.31  instead of normal 1.38 Â) together with the elon- Table 3. Hydrogen Bonding for the Complexes D-H-A d(D-H) (A) d(H-A) (A) d(D-A) (A) Angle(D-H-A) (°) 1 03-H3-N2i C6-H6-O411 C7-H7-O5" C19-H19B-O5iv 2 04-H4-N2v C6-H6-O5vi C7-H7-O3™ C16-H16B-O3™ 0.85(1) 2.00(2) 2.836(5) 167(7) 0.93 2.49(2) 3.359(5) 157(6) 0.93 2.55(2) 3.119(5) 120(6) 0.96 2.46(3) 3.279(6) 143(6) 0.85(1) 1.99(2) 2.826(4) 169(5) 0.93 2.46(3) 3.331(5) 156(5) 0.93 2.52(3) 3.091(5) 120(6) 0.96 2.49(3) 3.286(5) 140(5) Symmetry codes: (i) 1 - x, - y, ■ - x, 1 - y, - z; (viii) x, 1 + y, z. ■ z; (ii) x, 1/2 - y, -1/2 + z; (iii) 1 - x, 1 - y, - z; (iv) x, -1 + y, z; (v) 2 - x, 1 - y, 1 - z; (vi) x, 3/2 - y, -1/2 + z; (vii) Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures ... Acta Chim. Slov. 2016, 63, 279-286 283 gation of N(1)-N(2) bond length also supports the electron cloud delocalization in the ligand system.9b The aroylhydrazone Schiff base ligand forms a five-membered and a six-membered chelate rings with the Mo center. The dihedral angle between the two phenyl rings is 6.8(3)° for 1 and 5.9(5)° for 2. The trans angles between the donor atom of the methanol ligand and the oxo atom are 169.57(15)° for 1 and 169.78(13)° for 2, indicating considerable distortion of the coordination octahedron around the Mo(VI) center. It is usually that -Cl and -Br analogous derivatives perform isostructurality in the solid-state due Figure 1. ORTEP plots (30% probability level) and numbering scheme for 1. Figure 2. ORTEP plots (30% probability level) and numbering scheme for 2. Figure 3. Hydrogen bond (dashed lines) linked structure of 1, viewed down the c axis. Figure 4. Hydrogen bond (dashed lines) linked structure of 2, viewed down the c axis. to similar unit cell parameteres and moreover analogous crystal packings motifs. The crystal packing diagrams of the complexes are quite similar (Figure 3 and Figure 4). The two adjacent complex molecules are linked by two O-H—N hydrogen bonds (Table 3), to form dimer. The dimers are further linked through intermolecular hydrogen bonds of C-H—O, to form one-dimensional chains running along b axis. 3. 4. Catalytic Epoxidation Results Before addition of aqueous TBHP at 80 °C, the molybdenum complexes dissolve completely in the organic phase. The aqueous phase of the solution was colorless and the organic phase was yellowish, indicating that the catalyst is mainly confined in the organic phase. TBHP is mainly transferred into the organic phase under those conditions, and for that reason the reactant and products in the organic layer were analyzed. Cyclooctene and cyclooctene oxide are not significantly soluble in water, therefore the determination of the epoxide selectivity (epoxide formation/cyclooctene conversion) is expected to be accurate. The obtained results are given in Table 4. For the cyclooctene epoxidation by using aqueous TBHP, with no extra addition of organic solvents, the present study shows effective activity. Kinetic profiles of the molybdenum complexes as catalysts are presented in Figure 5. No induction time was observed. The cyclooctene conversion for the molybdenum complexes is high after 5 Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures 284 Acta Chim. Slov. 2016, 63, 279-286 Table 4. Catalytic Results for the Cyclooctene Epoxidation by Aqueous TBHPa Catalyst Conversion (%)b Selectivity (%)c TOF (h-1)d TONe 1 87 55 362 377 2 85 56 365 382 [MoO2(acac)2] 73 82 387 405 a Reaction conditions: time, 5 h; temperature, 80 °C. Molybdenum complex/cyclooctene/TBHP molar ratio: 0.25/100/200. b For cyclooctene, calculated after 5 h. c Formed epoxide per converted olefin after 5 h. d «(cyclooctene transformed)/n(catalyst)/time at 20 minutes. e «(cyclooctene transformed)/n(catalyst at 5 h). [MoO2(acac)2] is lower than the complexes, however, the selectivity is higher than the complexes. The usage of Mn-O2 is to decompose of excessive ieri-butyl hydroperoxide. MnO2 itself cannot oxidize cyclooctene to epoxycyclooc-tane. Possible mechanistic consideration involves coordination of TBHP as a neutral molecule, with the hydrogen bond O-H—O (Scheme 2). Even though high conversion of cyclooctene is observed, selectivity towards cycloocte-ne oxide is not high, 55% for 1 and 56% for 2. 4. Conclusion Figure 5. Kinetic monitoring of cù-cyclooctene epoxidation with TBHP-H2O in the presence of the molybdenum complexes. • represents 1, ■ represents 2. h, viz. 87% for 1 and 85% for 2. A negative control experiment using [MoO2(acac)2] as catalyst has been performed for comparison. The cyclooctene conversion for In summary, two new structurally similar cii-dioxo-molybdenum(VI) complexes with tridentate aroylhydra-zone ligands have been synthesized and characterized. The Mo atoms of the complexes are in octahedral coordination. The complexes can catalyze the epoxidation of cyclooctene, with high conversion but low selectivity. 5. Supplementary Material CCDC numbers 1433321 and 1433322 contain the supplementary crystallographic data for the complexes 1 and 2, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrie-ving.html, or from the Cambridge Crystallographic Data Center, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk. 6. Acknowledgments This work was financed by the National Technology Support Project (2012BAD36B03), the Open Foundation Scheme 2. Proposed mechanism for the catalytic process. Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures ... Acta Chim. Slov. 2016, 63, 279-286 285 of Zhejiang Provincial Top Key Academic Discipline of Chemical Engineering and Technology (YR2015004) and the Foundation of Wuhan Textile University. 7. References 1. (a) M. C. Heffern, V. Reichova, J. L. Coomes, A. S. Harney, E. A. Bajema, T. J. Meade, Inorg. Chem. 2015, 54, 90669074; http://dx.doi.org/10.1021/acs.inorgchem.5b01415 (b) S. Meghdadi, M. Amirnasr, M. Majedi, M. Bagheri, A. Amiri, S. Abbasi, K. Mereiter, Inorg. Chim. Acta 2015, 437, 64-69; http://dx.doi.org/10.1016Zj.ica.2015.08.006 (c) D. Qu, F. Niu, X. Zhao, K.-X. Yan, Y.-T. Ye, J. Wang, M. Zhang, Z. You, Bioorg. Med. Chem. 2015, 23, 1944-1949; http://dx.doi.org/10.1016/j.bmc.2015.03.036 (d) H. Zafar, A. Ahmad, A. U. Khan, T. A. Khan, J. Mol. Struct. 2015, 1097, 129-135; http://dx.doi.org/10.1016/j.molstruc.2015.04.034 (e) X. Zhao, X. Chen, J. Li, J. Chen, G. Sheng, F. Niu, D. Qu, Y. Huo, H. Zhu, Z. You, Polyhedron 2015, 97, 268-272. http://dx.doi.org/10.1016/j.poly.2015.07.012 2. (a) K.-H. Yang, Acta Chim. Slov. 2014, 61, 629-636; (b) S.S. Qian, X. Zhao, J. Wang, Z. You, Acta Chim. Slov. 2015, 62, 828-833; (c) L.-X. Li, Y. Sun, Q. Xie, Y.-B. Sun, K.-H. Li, W. Li, Z.-L. You, Chinese J. Inorg. Chem. 2016, 32, 369-376; (d) X. Zhao, X. Chen, J. Li, J. Chen, G. Sheng, F. Niu, D. Qu, Y. Huo, H. Zhu, Z. You, Polyhedron, 2015, 97, 268-272. http://dx.doi.org/10.1016/j.poly.2015.07.012 3. (a) R. G. Mohamed, F. M. Elantabli, N. H. Helal, S. M. El-Medani, Synth. React. Inorg. Met.-Org. Nano-Met. Chem. 2015, 45, 1839-1850; (b) T. S. M. Oliveira, A. C. Gomes, A. D. Lopes, J. P. Lou-renco, F. A. A. Paz, M. Pillinger, I. S. Goncalves, Dalton Trans. 2015, 44, 14139-14148; http://dx.doi.org/10.1039/C5DT02165K (c) C. A. Koellner, N. A. Piro, W. S. Kassel, C. R. Goldsmith, C. R. Graves, Inorg. Chem. 2015, 54, 7139-7141; http://dx.doi.org/10.1021/acs.inorgchem.5b01136 (d) T. Alemohammad, N. Safari, S. Rayati, M. Gheidi, A. Mortazavimanesh, H. Khavasi, Inorg. Chim. Acta 2015, 434, 198-208; http://dx.doi.org/10.1016/jica.2015.05.023 (e) M. Bagherzadeh, A. Ghanbarpour, H. R. Khavasi, Catal. Commun. 2015, 65, 72-75. http://dx.doi.org/10.1016/j.catcom.2015.02.023 4. (a) H. Y. Liu, L. Q. Zang, J. L. Lv, Russ. J. Coord. Chem. 2015, 41, 451-455; http://dx.doi.org/10.1134/S1070328415070052 (b) S. Morales-delaRosa, J. M. Campos-Martin, P. Terreros, J. L. G. Fierro, Topics in Catal. 2015, 58, 325-333; http://dx.doi.org/10.1007/s11244-015-0373-1 (c) T. Baskaran, R. Kumaravel, J. Christopher, T. G. Ajithku- mar, A. Sakthivel, New J. Chem. 2015, 39, 3758-3764. http://dx.doi.org/10.1039/C4NJ02402H 5. M. Amir, K. Shikha, Eur. J. Med. Chem. 2004, 39, 535-545. http://dx.doi.org/10.1016/j.ejmech.2004.02.008 6. G. J. J. Chen, J. W. McDonald, W. E. Newton, Inorg. Chem. 1976, 15, 2612-2615. http://dx.doi.org/10.1021/ic50165a008 7. (a) G. M. Sheldrick, SADABS, Siemens Analytical X-ray Instrument Division: Madison, WI, 1995; (b) G. M. Sheldrick, SHELXS97 Program for solution of crystal structures, University of Göttingen, Germany, 1997. 8. (a) Y.-T. Ye, F. Niu, Y. Sun, D. Qu, X.-L. Zhao, J. Wang, D.M. Xian, J. Hauser, Z.-L. You, Chinese J. Inorg. Chem. 2015, 31, 1019-1026; (b) Z.-L. You, D.-M. Xian, M. Zhang. CrystEngComm 2012, 14, 7133-7136. http://dx.doi.org/10.1039/c2ce26201k 9. (a) R. A. Lal, M. Chakrabarty, S. Choudhury, A. Ahmed, R. Borthakur, A. Kumar, J. Coord. Chem. 2010, 63, 163-175; http://dx.doi.org/10.1080/00958970903259451 (b) T. Glowiak, L. Jerzykiewicz, J. M. Sobczak, J. J. Ziol-kowski, Inorg. Chim. Acta 2003, 356, 387-392. http://dx.doi.org/10.1016/S0020-1693(03)00301-3 10. (a) R. Hahn, U. Kusthardt, W. Scherer, Inorg. Chim. Acta 1993, 210, 177-182; http://dx.doi.org/10.1016/S0020-1693(00)83325-3 (b) S. Gupta, A. K. Barik, S. Pal, A. Hazra, S. Roy, R. J. Butcher, S. K. Kar, Polyhedron 2007, 26, 133-141. http://dx.doi.org/10.1016/j.poly.2006.08.001 11. (a) L.-X. Li, Y. Sun, Q. Xie, Y.-B. Sun, K.-H. Li, W. Li, Z.-L. You, Chinese J. Inorg. Chem. 2016, 32, 369-376; (b) L. Pan, C. Wang, K. Yan, K. Zhao, G. Sheng, H. Zhu, X. Zhao, D. Qu, F. Niu, Z. You, J. Inorg. Biochem. 2016, 159, 22-28; http://dx.doi.org/10.1016/joinorgbio.2016.02.017 (c) D. Qu, F. Niu, X. Zhao, K.-X. Yan, Y.-T. Ye, J. Wang, M. Zhang, Z. You, Bioorg. Med. Chem. 2015, 23, 1944-1949. http://dx.doi.org/10.1016/j.bmc.2015.03.036 12. (a) M. Bagherzadeh, M. Amini, H. Parastar, M. Jalali-Hera-vi, A. Ellern, L. K. Woo, Inorg. Chem Commun. 2012, 20, 86-89; http://dx.doi.org/10.1016/j.inoche.2012.02.023 (b) R. Dinda, P. Sengupta, S. Ghosh, H. Mayer-Figge, W. S. Sheldrick, J. Chem. Soc. Dalton Trans. 2002, 23, 44344439. http://dx.doi.org/10.1039/b207129k 13. (a) R. Dinda, S. Ghosh, L. R. Falvello, M. Tomas, T. C. W. Mak, Polyhedron 2006, 25, 2375-2382; http://dx.doi.org/10.1016/j.poly.2006.02.002 (b) V. Vrdoljak, B. Prugovecki, D. Matkovic-Calogovic, J. Pisk, R. Dreos, P. Siega, Cryst. Growth Des. 2011, 11, 12441252. http://dx.doi.org/10.1021/cg1014576 Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures 286 Acta Chim. Slov. 2016, 63, 279-286 Povzetek Sintetizirali smo dva nova cis--dioksomolibdenova(VI) kompleksa s splošno formulo [MoO2L(MeOH)], kjer je L = L1 = N'-(3,5-dibromo-2-hidroksibenziliden)-4-trifluorometilbenzohidrazid (1) oziroma L = L2 = N'-(3-bromo-5-kloro-2-hidroksibenziliden)-4-trifluorometilbenzohidrazid (2) ter ju okarakterizirali z elementno analizo, FT-IR, molsko prevodnostjo in UV-Vis spektroskopijo. Kompleksa sta bila strukturo okarakterizirana tudi z monokristalno rentgensko difrakcijo. Kompleksa imata popačeno oktaedrično strukturo z aroilhidrazonom kot dianionskim ligandom. Iz kristalne strukture je razvidno, da ima Mo(VI) center NO5 donorsko okolje ter da sta del oktaedrične strukture dve oksido skupini in atom kisika iz molekule metanola. Katalitične lastnosti so bile raziskane na primeru epoksidacije ciklooktena z uporabo vodne raztopine terc-butil hidroperoksida kot oksidanta. Liu et al.: Synthesis, Characterization and X-Ray Crystal Structures ... DOI: 10.17344/acsi.2015.2181 Acta Chim. Slov. 2016, 63, 287-297 287 Scientific paper Solid-liquid Extraction of Phenolics from Red Grape Skins Ivana Tomaz,1* Luna Maslov,1 Domagoj Stupi},1 Darko Preiner,1 Danijela A{perger,2 and Jasminka Karoglan Konti}1 1 Department of Viticulture and Enology, Faculty of Agriculture, University of Zagreb, Sveto{imunska 25, 10000 Zagreb, Croatia 2 Department of Analytical Chemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Marulicev trg 19, 10000 Zagreb, Croatia * Corresponding author: E-mail: itomaz@agr.hr Received: 15-12-2015 Abstract For the characterization of grape cultivars, the profile and content of flavonoids are important because these compounds have an impact on grape and wine quality. A new extraction method for the recovery of flavonoids, e.g. anthocyanins, flavonols and flavan-3-ols from grape skins was developed. The optimization of solid-liquid extraction of flavonoids was conducted, with respect to the type of the organic solvent and its percentage in the extraction solvent as well as the extraction temperature and extraction time, using response surface methodology. Optimal conditions were obtained by using extraction solvent composed from acetonitrile:water:formic acid (20:79:1; v/v/v), at an extraction temperature of 50 °C, an extraction time of 1 h in a single-step extraction and with a solid-to-solvent ratio of 1:80 g mL-1 (125 mg of grape skin powder and 10 mL of extraction solvent). The new optimal extraction method is inexpensive, simple, fast, accurate and selective for the recovery of simple flavonoids. Keywords: Grape skins; solid-liquid extraction; flavonoids; multi-response optimization 1. Introduction Phenolics are a large and structurally diverse class of molecules present in different plant spacies which could be divided in many subgroups based on their structure. Flavo-noids are one of the largest phenolic subgroup which play a very important role in growth, reproduction and in various defense reactions in plants. Based on the oxidation state of phenol rings in the flavonoid structure, they can be divided to anthocyanins, flavonols, flavan-3-ols, flavanones, isoflavones, chalcones, flavananols and xanthones. Many of these compounds have biological activities like antioxi-dative, antifungal, antimicrobial and anti-inflammatory properties thus they have a positive effect on human health.1,2 Grapes contain large amount of different flavonoids such as anthocyanins, flavonols and flavan-3-ols.3 In the last decade a variety of new extraction techniques have been developed such as ultrasound assisted extraction (UAE), microwave assisted extraction (MAE), supercritical fluid extraction (SFE) and many others. These techniques may be applied for the extraction of phenolics from different plant matrices. Based on the literature, it is evident that application of these techniques for extraction of phenolics from grape skins is very rare. There is only a few studies concerning UAE,4'5 MAE6 and SFE.7 Application of SFE for extraction of phenolics is limited due to their polarity. In our last study UAE method was optimized for the recovery of flavonoids from grape skins,4 but nowadays SLE is the most used technique for extraction of phenolics from the grape skins.8-16 This extraction technique has many advantages, the most important being no need to invest in new equipment and the possibility of extracting multiple samples at once. Thus, these facts greatly reduce the price of the analysis, and increase the efficiency of labor in cases where it is necessary to analyze large numbers of samples. Over the past six decades, hundreds of publications on analysis of grape phenolic compounds have been published, but there is still no available standardized procedure for the extraction.17 Different authors used different extraction conditions for recovery of Tomaz et al.: Solid-liquid Extraction of Phenolics 288 Acta Chim. Slov. 2016, 63, 287-297 flavonoids from grape skins. Solvents, like methanol,8-10 acetone,18 ethyl acetate,19 ethanol11 and their combination with different portions of water with or without addition of acid,12-15,20 are the common extraction solvents for recovery of flavonoids from grape berry skin. Portion of water can be from 0%8-10 to 50%.11-1520 One of the most commonly used extraction solvent is a mixture of etha-nol:water:formic acid (70:29:1, v/v/v).12,15,21 Extraction time can be less than 5 min14,15 to up to few days9 while the temperature can be from 4 °Cn to 70 °C.22 Solid-to-solvent ratio and number of extraction steps are parameters that have great influence on extraction yield and they can be in the range from 1:216 to 1:80 g mL-1 22 and from 18,12,14,21 to 9,10 respectively. From the quantitative point of view, results obtained by different extraction methods could not be compared, because different extraction conditions would have different extraction efficiency. Thus the aim of the present study was to optimize the most popular extraction technique, SLE, to obtain the best extraction conditions for the recovery of individual flavonoids from grape berry skins. Several parameters: the type of organic solvent, the percentage of organic phase in the extraction solvent, the extraction temperature and the extraction time, which could affect the extraction efficiency were evaluated and optimized using a response surface methodology (RSM) and employing a Box-Behn-ken experimental design (BBD). 2. Experimental 2. 1. Chemicals Acetonitrile and methanol of HPLC grade were purchased from J. T. Baker (Deventer, Netherlands). Formic acid and 85% orthophosphoric acid were obtained from Fluka (Buchs, Switzerland). Ethanol and acetone were provided from Kemika (Zagreb, Croatia). The standards used for identification and quantification purposes were as follows: delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, peonidin-3-O-glucoside, malvi-din-3-O-glucoside, delphinidin-3,5-O-diglucoside, cyani-din-3,5-0-diglucoside, malvidin-3,5-0-diglucoside, epi-gallocatechin, procyanidin B1, procyanidin B2, rutin, and myricetin (Extrasynthese, Genay Cedex, France); (-)-epi-catechin and (+)-catechin (Sigma-Aldrich, St. Louis, MO, USA); kaempferol, quercetin-3-O-glusoside and isorham-netin (Fluka, Steinheim, Germany); quercetin-3-O-gluco-side (Sigma, St. Louis, MO, USA). All standards were analytical standard grade. 2. 2. Grape Preparation Grape samples ('Regent') were obtained in 2012 and 2013 from the vineyard located at the Experimental station Jazbina, Faculty of Agriculture, University of Zagreb, Croatia. Grapes were harvested in a state of full ripeness and immediately separated from the stalk. To obtain homogenous samples of the berries at a similar level of ripeness (sugar and flavonoid content), a simple flotation method was used with sucrose water solutions of different densities. Grape berries with a density range of 1.088 to 1.099 g cm-3 were selected for further analysis. The berry skins were manually removed from the pulp and freeze-dried. Dry skins were ground (Coffee Grinder SMK150, Gorenje, Slovenia) and powder obtained was stored (2 °C) in a glass container. 2. 3. Extraction of Flavonoids from Grape Skin All experiments were completed on a magnetic stirrer (RCT basic, IKA, Staufen, Germany) at 400 rpm. After extractions were complete, supernatants were collected, concentrated under a vacuum to remove organic modifier (40 °C) on a Hei-Vap Adventage G3 rotary evaporator (Heidolph, Schwabach, Germany) and brought to a final volume of 10 mL with eluent A (water:phosphoric acid, 99.5:0.5, v/v). The extracts were filtered with a Phe-nex-PTFE (polytetrafluorethylene) 0.20 pm syringe filter (Phenomenex, Torrance, USA) and analyzed by HPLC. Before setting the levels of the studied factors some preliminary experiments using the one-factor-at-the-time methodology were necessary. For determination of appropriate organic phase in extraction solvent the following extraction solvents composed of ethanol:water (70:30; v/v), methanol:water (70:30 v/v) and ethanol:water:formic acid (70:29:1; v/v/v) were used. Temperature and time of extraction was 30 °C and 3 h, respectively, while the extractions were performed in a single step with the solid-to-solvent ratio of 1:80 g mL-1 (125 mg of grape skins powder and 10 mL of the extraction solvent). The optimal range of extraction time (30 min-24 h) was determined in a single-step extraction by an extraction solvent composed of ethanol:water:formic acid (70:29:1; v/v/v). The solid-to-solvent ratio was 1:80 g mL1 (125 mg of grape skins powder and 10 mL of the extraction solvent) while the temperature was 30 °C. The extract was centrifu-ged in a LC-321 centrifuge (Tehtnica, Železniki, Slovenia) for 20 min at 5000 rpm at room temperature. All experiments were performed in triplicate. 2. 4. Experimental Design and Statistical Analysis After determining the optimal conditions of the extraction factors through the single-factor tests, the effect of the three numerical factors (the percentage of organic phase in the extraction solvent, the extraction temperature and the extraction time) and one categorical factor (the type of organic solvent) on the content of individual anthocyanins, flavonol glycosides and flavan-3-ols were studied through the Box-Behnken experimental design and response surface methodology. The BBD is very efficient for studies with a high number of factors.23 These four independent factors Tomaz et al.: Solid-liquid Extraction of Phenolics ... Acta Chim. Slov. 2016, 63, 287-289 297 Table 1. Independent factors and their levels used in the response surface design Factors Factor level Coded levels -1 0 1 A: Percentage of organic solvent (%) 20 50 80 B: Extraction temperature (°C) 30 45 60 C: Extraction time (h) 12 3 D: Type of organic solvent Acetonitrile Ethanol Acetone were investigated at three different coded levels (Table 1). Extraction solvents were composed of appropriate percentage of organic solvent (20, 50 and 80%), water (79, 49 and 19%) and 1% of formic acid. In all experiments solid-to-solvent ratio was fixed at 1:80 g mL1 which means that mass of grape skin powder was 125 mg while the volume of appropriate extraction solvent was 10 mL. The resulting contents of the 3-O-glucoside and 3,5-O-diglucoside of delphinidin, cyanidin, peonidin and mal-vidin; those of 3-O-glycoside quercetin, myricetin, kaempferol and isorhamnetin and those of gallocatechin, procyanidin B1, procyanidin B2, catechin, epicatechin and epigallocatechin were used as responses (Y, dependent variables). The results of the BBD experiments were analyzed by non-linear multiple regression with backward elimination to fit the following second-order equation to the dependent Y variables: Y = P0 + SPx + Sftxx + SPx2 (I = 1, 2...k) (1) P0, Pj, Pjj and Pjj are the coefficients for the linear, quadratic and interaction effects, respectively, xi and x. are ij the levels of independent factors in the coded values. Coefficients were interpreted using an F-test. To establish the optimum conditions for individual anthocyanin, flavo-nol glycoside and flavan-3-ol contents, analysis of variance (ANOVA), regression analysis and plotting of the response surface plot were conducted. For optimization mul-ticriteria methodology (Derringer function or desirability function) was used. This methodology is applied when various responses must be considered at the same time, and it is necessary to find optimal compromises between the total number of considered responses. The optimal experimental conditions were based on the maximal content of the individual flavonoids.24 The analysis of the experimental design and calculation of the predicted data was completed using the Design Expert software (Trial Version 9.0.3.1, Stat-Ease Inc., Minneapolis, USA). The mean values, standard deviations and significant differences of the data were calculated and reported using OriginPro 8 (OriginLab Corporation, Northampton, USA). The results were analyzed with ANOVA and the differences between the means were evaluated by Tukey's post-hoc test at a confidence level of 95% (p < 0.05). The data reported in all of the tables were the average of triplicate observation. 2. 5. HPLC Analysis Separation, identification and quantification of flavonoids from grape skin extracts were performed according to the method described by Tomaz and Maslov25 on an Agilent 1100 Series system (Agilent, Germany), equipped with autosampler, column thermostat, diode array detector (DAD) and fluorescence detector (FLD). The separation was performed with a reversed-phase column Luna Phenyl-Hexyl (4.6 x 250 mm; 5 pm particle (Phenome-nex, Torrance, USA)) heated at 50 °C. The solvents were water:phosphoric acid (99.5:0.5, v/v, eluent A) and aceto-nitrile:water:phosphoric acid; 50:49.5:0.5, v/v/v, eluent B), and the flow rate was 0.9 mL min-1. The gradient for eluent B was: 0 min, 0%; 7 min, 20%; 35 min, 40%; 40 min, 40%; 45 min, 80%; 50 min, 100%; 60 min 0%. The injection volume for all samples was 20 pL. Flavonol glycosides were detected at 360 nm while anthocyanins at 518 nm using DAD, while flavan-3-ols were detected at Aex = 225 nm and Aem = 320 nm by means of FLD. 2. 6. LC-MS Analysis For peak assignment, grape skin extracts were analyzed with Agilent 1200 Series system (Agilent, Germany) coupled on-line to an Agilent model 6410 mass spectrometer fitted with ESI source. The separation was performed with column described in the previous section with the solvents water:formic acid (99.5:0.5, v/v, eluent A) and aceto-nitrile:water:formic acid; 50:49.5:0.5, v/v/v, eluent B). Eluation gradient was same as previously described while the flow rate was 0.5 mL min1. The mass spectra of fla-van-3-ols and flavonols were recorded in the negative mode while those of anthocyanins in the positive mode. Negative and positive ion mass spectra of column eluate were recorded in the range m/z 100-1000. The electrospray ioni-zation (ESI) parameters were as following; drying gas (N2) flow and temperature, 8 L min-1 and 300 °C, nebulizer pressure 30 psi, capillary voltage 4500 V for negative ion mode or -4500 V for positive ion mode. Fragmentation voltage was 135 V.25 2. 7. Quantification of Individual Compounds from Grape Skin Extracts Individual flavonoids in grape berry skin extracts were identified by matching the retention time of each chro- Tomaz et al.: Solid-liquid Extraction of Phenolics 290 Acta Chim. Slov. 2016, 63, 287-297 matographic peak with external standards and DAD spectrum. Quantification of individual flavonoid peaks was done by using a calibration curve of the corresponding standard compound which was based on the peak area. Range for calibration curves and related regression equation together with limits of detection and limits of quantification were described in our previous study.25 When reference compounds were not available, the calibration by a structurally related compound was used. For quantification of myrice-tin-3-O-glucoside, kaempferol-3-O-glucuronide and isor-hamnetin-3-O-glucoside appropriate aglycons were used. Contents of gallocatechin and peonidin-3,5-0-diglucoside were expressed in epigallocatechin and peonidin-3-O-glu-soside equivalents. Results are expressed in mg kg-1 of dry weight (d.w.) of grape skin. In preliminary tests contents of particular class of flavonoids, namely anthocyanin contents (AC), flavonol glycoside contents (FGC) and flavan-3-ol contents (FC), were expressed as sum of content of individual compounds determined by HPLC. 3. Results and Discussion Cultivar 'Regent' is one of the successful newly bred varieties obtained by back-crossing hybrids of Vitis vinife-ra L. and some other Vitis species possessing fungal resi- stance, with high quality grapevine cultivars. Species V vinifera contains only anthocyanin-3-monoglucosides while most of other Vitis species together with anthocya-nin-3-monoglucosides contain dominant allele for synthesis of anthocyanin-3,5-diglucosides. Thus, this characteri- Fig. 1. Chromatogram of anthocyanins recorded at 518 nm. Peak assignation: 1. Delphinidin-3,5-O-diglucoside, 2. Cyanidin-3,5-O-diglucoside, 3. Delphinidin-3-O-glucoside, 4. Peonidin-3,5-O-di-glucoside, 5. Malvidin-3,5-O-diglucoside, 6. Cyanidin-3-O-gluco-side, 7. Peonidin-3-O-glucoside, 8. Malvidin -3-O-glucoside Table 2. Effect of the extraction solvent composition on the contents of individual flavonoids from grape skins. Results are expressed as mg kg 1 dry weight of grape skin Compound 70% Methanol Y ± SD 70% Ethanol Y ± SD 70% Ethanol + 1% formic acid Y ± SD Delphinidin-3,5-O-diglucoside 864.36 ± 24.73a 1040.47 ± 10.71b 1340.47 ± 4.01c Cyanidin-3,5-O-diglucoside 1122.89 ± 29.73a 1171.23 ± 7.46a 1347.41 ± 7.50b Delphinidin-3-O-glucoside 9284.13 ± 71.73a 9006.86 ± 73.90b 10960.35 ± 61.00c Peonidin-3,5-O-diglucoside 954.63 ± 4.51a 940.65 ± 5.27a 1127.25 ± 14.01b Malvidin-3,5-O-diglucoside 13630.26 ± 30.00a 13909.08 ± 44.76b 15766.92 ± 57.85c Cyanidin-3-O-glucoside 1796.35 ± 12.91a 1716.18 ± 13.86b 2053.23 ± 10.01c Peonidin-3-O-glucoside 485.82 ± 7.51a 508.18 ± 8.83a 590.17 ± 11.00b Malvidin -3-O-glucoside 6783.82 ± 10.71a 6988.87 ± 50.23b 7832.98 ± 30.00 c Total anthocyanins 34922.26 ± 105.34a 35281.52 ± 100.76a 41018.78 ± 110.32b Myricetin-3-O-glucoside 481.91 ± 5.54a 528.04 ± 7.00b 550.44 ± 11.83c Rutin 245.11 ± 5.02a 250.71 ± 4.27a 255.11 ± 5.03a Quercetin-3-O-glucoside 1587.82 ± 15.27a 1661.67 ± 10.50b 1720.70 ± 16.91c Kaempferol-3-O-glucuronide 54.06 ± 5.49a 69.61 ± 9.51b 111.01 ± 10.03c Isorhamnetin-3-O-glucoside 92.57 ± 2.44a 106.11 ± 4.47b 110.14 ± 2.02b Total flavonol glycosides 2462.47 ± 9.37a 2616.14 ± 10.32b 2747.40 ± 18.82c Gallocatechin 6.06 ± 1.01a 7.27 ± 1.94a 11.02 ± 0.97b Procyanidin B1 49.16 ± 2.02a 53.18 ± 3.04ab 59.05 ± 2.09b Epigallocatechin 25.32 ± 2.08a 24.04 ± 3.12a 36.71 ± 1.03b Catechin 7.73 ± 2.52a 14.25 ± 3.03b 12.48 ± 2.49b Procyanidin B2 0.73 ± 0.64a 0.66 ± 0.57a 17.68 ± 0.64b Epicatechin 20.54 ± 1.53a 20.77 ± 3.68a 26.93 ± 0.91b Total flavan-3-ols 109.54 ± 3.22a 120.17 ± 5.65b 163.87 ± 4.87c Y mean value (n -rence p < 0.05 3). SD standard deviation. Superscript letters a, b, and c indicate grouping within a row. Different letters show statistical diffe- Tomaz et al.: Solid-liquid Extraction of Phenolics ... Acta Chim. Slov. 2016, 63, 287-291 297 stic was retained in 'Regent' and it contains anthocyanin-3,5-diglucosides together with anthocyanin-3-monoglu-cosides (Fig. 1). This cultivar contains very high content of flavonols and flavan-3-ols, as well.26 3. 1. Effect of the Extraction Solvent Composition on the Recovery of Flavonoids from Grape Skins The extraction efficiency is strongly dependent on the type of solvent. Solubility of flavonoids is governed by the polarity of the solvents used. Depending on the solvent system used for the extraction, a mixture of different compounds, such as flavonoids and non-phenolic compounds (sugars, organic acids and fats) soluble in the solvent will be extracted from grape berry skins. Selection of the appropriate extraction solvent is necessary to achieve excellent effectiveness and good selectivity. Methanol and ethanol have similar physico-chemical properties. Some experiments were conducted to make a choice which alcohol will be used in further studies. In these experiments, extraction solvents were composed of 70% of appropriate alcohol in water. For the most of the examined compounds from grape skins, ethanol was better organic solvent (Table 2). This finding could be explained by the viscosity of alcoholic solutions. Water solutions of methanol are more viscous than equivalent ethanolic solutions.27,28 The diffusion of the analytes from the solid samples to the bulk solvent is facilitated in the media of low viscosity. This observation is in accordance with results obtained by Lapornik et al.16 So based on obtained results and the fact that ethanol is environmentally benign and relatively safe for human health, it was chosen as an organic modifier in the following experiments. According to the literature, acetone is an excellent solvent for the recovery of flavan-3-ols and particularly for the extraction of oligomeric and polymeric forms from grape skins. Based on the experience gained during development of the HPLC method for the separation of phenolics,25 ace-tonitrile was selected as a third organic phase. Flavonoids, especially anthocyanins, are the most stable at very low pH when they are in flavylium form; so it is necessary to conduct extraction in an acidic environment. Acylated anthoc-yanins and flavonol glycosides are labile in solutions containing mineral acid thus it is mandatory to add a weaker acid such as formic acid to the extraction solvent. By adding formic acid in the extraction solvent, a significant recovery increase was observed for all of the examined flavonoids from grape skins (Table 2). Bakker et al.29 showed that artefacts such as formylated derivates of anthocyanins can be obtained using an extraction solvent containing 2% formic acid. By close inspection of the chromatograms recorded at 518 nm after injection of the extract obtained by extraction solvent containing 1% formic acid, these artefacts were not observed. Based on the obtained results extraction solvents with the appropriate organic phases and 1% of formic acid were selected for further experiments. 3. 2. Effect of the Extraction Time on the Recovery of Flavonoids From Grape Skins The contents of anthocyanins, flavonol glycosides and flavan-3-ols from grape skins at different extraction times are presented in Fig. 2. Extraction was conducted ,42000- TO E 40000- i 41000-c 0) e O o tn c 'c CO U 39000- -C s= < a) l-l \ 38000 i—i—i—i—i—.—i—.—i—.—i—.—i—i—i—i—i—i—i—.—r 0.5 1 2 3 4 6 8 16 20 24 Time / h ra 2300 c o o CD "2 U) o Q o> 22502200 2150 2100 20502000 c 1950-o ro 1900 b) -I—I- 0.5 1 2 3 4 6 8 16 20 24 Time / h - 200-, '01 190- U) g 180- i. a> 170- c_ o o 160- o CO 150- c CO > 140- CO u_ 130- c) r/1 Jt—I_I—I—I—I I—$ 1 ± 1 I I '—\—1—I- 0.5 1 —i—i—i—i—r— 3 4 6 Time / h -1—<—i—'—r~ 16 20 24 Fig. 2. Effect of extraction time on a) anthocyanin contents; b) flavonol glycoside contents and c) flavan-3-ol contents from grape skins. Other extraction conditions were as follows: single-step extraction by an extraction solvent composed of ethanol:water:formic acid (70:29:1; v/v/v), the solid-to-solvent ratio of 1:80 g mL-1 and temperature of 30 °C. Tomaz et al.: Solid-liquid Extraction of Phenolics 292 Acta Chim. Slov. 2016, 63, 287-297 for different time periods (30 min, 1, 2, 3, 4, 6, 8, 16, 18, 20 and 24 h) while the following factors were constant: solid-to-solvent ratio 1:80 g mL1, single-step extraction and temperature of 30 °C. A significant increase of AC was observed between 1 and 3 h. The same trend follows FGC and FC. Longer extraction times led to a slight decrease of AC and FGC but FC remained at a steady value. Therefore, in the experimental design time periods between 1 and 3 h were used. 3. 3. Optimization of Extraction Conditions by Response Surface Methodology For the optimization of the best extraction conditions of flavonoids from grape skins, research was focused on the effect of the extracting solvent (percentage of organic modifier), extraction time and temperature. The 45 experimental conditions, including three replicates at the center point, were chosen (Supplemental Table 1). All of the target compounds were best described by a quadratic polynomial model. Catechin was best described by a linear model. Parameters describing a model are presented in Supplemental Table 2. The effect of solvent type was the most significant factor. The effect of acetonitrile, ethanol and acetone are described in Table 4. The highest contents of the great majority of the examined compounds from grape skins were obtained using acetonitrile as organic modifier (Table 3). Different percentage of organic modifier was also examined, and the best recoveries were at 20%. An enhancement in the extraction temperature increased anthocyanins and flavonol glycosides recoveries. The optimal temperature for extraction of these phenolic compounds was up to 50 °C. At higher temperatures significant decomposition of anthocyanins and flavonol glycosides was noticed. The optimum extraction time of 1 h was sufficient extraction time for almost all of the target analytes. A prolonged time of extraction showed to have a positive effect on the recovery of fla-van-3-ols. The interactions of the extraction factors were studied from the contour plots generated by the model. It was observed that for the most compounds from grape skins, a clear interaction between the various extraction factors exists (Figs. 3-5). The most frequent interaction effect was observed between the percentage of the organic phase in the extraction solvent and the extraction temperature. Raising the temperature reduces the viscosity of the extraction solvent and enhances extraction. The percentage of organic modifier in the extraction solvent had a great effect on the polarity of the extraction media. According to the well-known principle for predicting solubility »like dissolves like«, the optimal ex- Table 3. Optimal extraction conditions for the recovery of individual and all together flavonoids determined by response surface methodology. Predicted and experimental values are expressed in mg kg-1 dry weight of grape skin Compound Organic modifier Percentage of organic phase (%) Temperature (°C) Time (h:min) Desirability Predicted values Experimental values Y ± SD Delphinidin-3,5-0-diglucoside Ethanol 64 46 1:02 1.000 1596.26 1589.37 ± 9.27 Cyanidin-3,5-0-diglucoside Ethanol 20 45 1:00 1.000 1559.22 1548.48 ± 16.34 Delphinidin-3-O-glucoside Acetonitrile 20 43 1:00 1.000 12346.60 12362.42 ± 55.31 Peonidin-3,5-0-diglucoside Ethanol 20 49 1:00 1.000 1158.68 1143.67 ± 12.23 Malvidi-3,5- O-diglucoside Acetonitrile 20 45 1:00 1.000 16772.28 16738.07 ± 44.03 Cyanidin-3-O-glucoside Acetonitrile 20 39 1:00 1.000 2499.56 2471.87 ± 22.66 Peonidin-3-O-glucoside Acetonitrile 20 42 1:00 1.000 664.81 658.22 ± 7.19 Malvidin -3-0-glucoside Acetonitrile 20 45 1:00 1.000 8947.09 8930.59 ± 40.18 Total anthocyanins Acetonitrile 21 44 1:00 1.000 44524.03 44987.32 ± 59.32 Myricetin-3-O-glucoside Ethanol 20 45 1:00 1.000 658.19 637.76 ± 12.81 Rutin Ethanol 20 45 1:00 1.000 310.58 307.21 ± 16.01 Quercetin-3-O-glucoside Acetonitrile 80 45 1:00 1.000 1944.26 1951.61 ± 9.75 Kaempferol-3-O-glucuronide Acetonitrile 20 50 1:36 1.000 83.05 81.30 ± 5.15 Isorhamnetin-3-O-glucoside Acetonitrile 20 41 1:18 1.000 122.83 119.06 ± 7.42 Total flavonol glycosides Acetonitrile 21 45 1:04 1.000 3249.22 3265.32 ± 15.38 Gallocatechin Acetonitrile 70 40 1:00 1.000 16.71 15.84 ± 1.32 Procyanidin B1 Acetone 80 60 1:37 1.000 92.11 93.47 ± 3.97 Epigallocatechin Acetonitrile 21 59 3:00 1.000 43.23 40.94 ± 2.07 Catechin Acetonitrile 80 60 3:00 1.000 28.78 28.57 ± 1.25 Procyanidin B2 Acetone 20 60 1:00 1.000 43.83 42.03 ± 1.97 Epicatechin Acetronitrile 20 60 1:00 1.000 32.35 34.72 ± 3.06 Total flavan-3-ols Acetonitrile 20 60 2:00 1.000 229.58 220.34 ± 8.25 All together Acetonitrile 20 50 1:00 0.797 Tomaz et al.: Solid-liquid Extraction of Phenolics ... Acta Chim. Slov. 2016, 63, 287-293 297 traction yield may be achieved when the polarity of the extraction solvent and analytes coincide. When the optimum viscosity and polarity are fulfilled, the maximum extraction yield was achieved. For nearly all of the studied anthocyanins from grape skins optimum temperature is around 45 °C with 20% acetonitrile in the extraction solvent (Fig. 3.). In the case of some compounds, namely delphini-din-3-O-glucoside, delphinidin-3,5-0-diglucoside (Fig. 3.) and procyanidin B2 (Fig. 4.) the interaction between the extraction time and the percentage of organic modifier in the extraction solvent are the most important ones. This observation could be explained by the polarity. The dissolution of the target analytes is faster in the Fig. 3. Contour plots of most prominent interaction factors for individual anthocyanins from grape skins using acetonitrile as organic modifier. Cy dglc - Cyanidin-3,5-0-diglucoside; Cy glc - Cyanidin-3-O-glucoside; Del glc - Delphinidin-3-O-glucoside; Del dglc - Delphinidin-3,5-0-di-glucoside; Mv dglc - Malvidin-3,5-0-diglucoside; Mv glc - Malvidin-3-O-glucoside; Pd dglc - Peonidin-3,5-0-diglucoside; Pd glc - Peonidin-3-O-glucoside. Tomaz et al.: Solid-liquid Extraction of Phenolics 294 Acta Chim. Slov. 2016, 63, 287-297 solvent of suitable polarity so the extraction time is shorter. Interaction between the time and the temperature had a significant effect on the extraction of the majority of examined flavan-3-ols (Fig. 4.) and quercetin-3-0-glucoside (Fig. 5.). The increase in the extraction time and the extraction temperature caused an increase in the recovery of flavan-3-ols from grape skins. These findings could be explained by the position of these compounds in the grape skin cells. They could be bound to the cell wall of grape skin so for the effective extraction of these compounds it is necessary to disrupt cell wall. Disruption of cell walls is enhanced in an acidic environment and at a higher temperature.30'31 The decrease in the extraction temperature and time had a positive effect on quercetin-3-O-glucoside recovery. This compound is thermally unstable and prolonged extraction at higher temperature led to its decomposition. The optimization of extraction conditions for individual responses as well as for all individual compounds together from grape skins is presented in Table 4. Multicri- teria methodology (Derringer function or desirability function) was used. The examination of optimal extraction conditions was based on the maximum recovery of individual anthocyanins' flavonol glycosides' and flavan-3-ol from grape skins (Supplemental Fig.1). The optimized conditions were as follows: extraction solvent composed of acetonitrile:water:formic acid (20:79:1; v/v/v), at an extraction temperature of 50 °C, extraction time of 1 h and in a single-step extraction with a solid-to-solvent ratio of 1:80 g mL-1 (125 mg of grape skin powder and 10 mL of extraction solvent). The optimized conditions obtained by RSM were used to verificate the predictive model of extraction of phenolics from the red grape skin. The results (Table 3 and Table 4) showed that the experimental and predicted values differentiate for less than 1.5%. To validate the new optimized SLE method, the reproducibility and precision were determined. The reproducibility and the precision of the optimized SLE method were satisfactory. The calculated RSD values were less than 5% for all of the examined compounds from grape skins. The Fig. 4. Contour plots of most prominent interaction factors for individual flavan-3-ols from grape skins using acetonitrile as organic modifier. EC - Epicatechin; EGC - Epigallocatechin; GC - Gallocatechin; B1 -Procyanidin B1; B2 - Procyanidin B2. Tomaz et al.: Solid-liquid Extraction of Phenolics ... Acta Chim. Slov. 2016, 63, 287-295 297 Fig. 5. Contour plots of most prominent interaction factors for individual flavonols from grape skins using acetonitrile as organic modifier. I glc - Isorhamnetin-3-O-glucoside; K glr - Kaempferol-3-O-glucuronide; My glc - Myricetin-3-O-glucoside; Q glc - Quercetin-3-O-glucoside; Rut - Rutin. highest RSD values were calculated for individual fla-van-3-ols. This can be explained by their low content and chemical nature (Table 4). During extraction, these compounds can hydrolyze, isomerize or can arise as hydrolysis products of tannins. A low percentage of ace-tonitrile exists in the extraction solvent so there is no need for it to be removed by evaporation in a vacuum before HPLC analysis, which greatly improves the precision and accuracy of the method and also contributes to a low RSD value. 4. Conclusion The RSM was successfully employed to optimize solid-liquid extraction of flavonoids from grape berry skins. For the first time, the effect of different types of organic modifier in the extraction solvent on the extraction efficiency is considered. For optimization of extraction conditions, a multi-response methodology was applied for the first time. This study clearly demonstrates that numerous factors have great effect on extraction efficiency, such as the type of organic modifier and its percentage in the extraction solvent, the extraction time and temperature and in particular the nature of analytes and their position within the grape skin cell, have a great effect. Optimal extraction conditions may vary significantly, even for the members of the same group of flavonoids. The results revealed that SLE using extraction solvent composed from acetonitrile:water:formic acid (20:79:1; v/v/v), at the extraction temperature of 50 °C, extraction time of 1 h in single-step extraction and with the solid-to-solvent ratio of 1:80 g mL-1 (125 mg of grape skin powder and 10 mL of extraction solvent) is an effective method for the recovery of flavonoids from grape skins. The great advantage of applying this new optimized SLE method is the reduction of the number of operations throughout the extraction process; there is no longer a need for the organic modifier Tomaz et al.: Solid-liquid Extraction of Phenolics 296 Acta Chim. Slov. 2016, 63, 287-297 Table 4. The content of individual flavonoids extracted from grape skins by using optimal conditions. Results are expressed in mg kg 1 dry weight of grape skin Compound Predicted values Experimental values (n Y ± SD = 3) RSD Delphinidin-3,5-0-diglucoside 795.88 793.70 ± 1.59 0.20 Cyanidin-3,5-0-diglucoside 1452.81 1448.29 ± 7.10 0.49 Delphinidin-3-O-glucoside 12256.80 12270.98 ± 49.95 0.41 Peonidin-3,5-0-diglucoside 1153.01 1162.60 ± 7.33 0.63 Malvidin-3,5-0-diglucoside 16803.90 16735.50 ± 34.33 0.21 Cyanidin-3-ö-glucoside 2413.40 2401.35 ± 12.16 0.51 Peonidin-3-O-glucoside 664.81 658.22 ± 7.19 1.09 Malvidin -3-0-glucoside 8888.49 8936.18 ± 43.01 0.48 Total anthocyanins 44522.20 44406.82 ± 110.34 0.25 Myricetin-3-ö-glucoside 647.05 639.17 ± 4.74 0.74 Rutin 304.76 307.32 ± 6.40 2.08 Quercetin-3-O-glucoside 1864.52 1852.36 ± 13.05 0.70 Kaempferol-3-O-glucuronide 82.35 84.34 ± 3.31 3.91 Isorhamnetin-3-O-glucoside 121.59 119.66 ± 3.84 3.21 Total flavonol glycosides 3229.92 3302.85 ± 20.67 0.63 Gallocatechin 12.99 12.14 ± 0.32 2.64 Procyanidin B1 80.75 83.24 ± 3.82 4.59 Epigallocatechin 40.33 39.79 ± 1.37 4.44 Catechin 18.68 18.05 ± 0.74 4.07 Procyanidin B2 41.40 42.48 ± 2.12 4.99 Epicatechin 30.92 29.94 ± 0.86 2.87 Total flavan-3-ols 225.13 223.64 ± 5.43 2.42 Y mean value (n = 3). SD standard deviation. RSD relative standard deviation in the extraction solvent to be removed. Therefore any possible errors that may arise during frequent sample transfer from one vessel to another can be avoided. 5. References 1. K. B. Pandey, S. I. Rizvi, Oxidative Medicine and Cellular Longevity, 2009, 2, 270-278. http://dx.doi.org/10.4161/oxim.2.5.9498 2. G. Agati, E. Azzarello, S. Pollastri,M. Tattini, Plant science, 2012, 196, 67-76. http://dx.doi.org/10.1016/j.plantsci.2012.07.014 3. A. P. B. Gollucke, Recent Patents on Food, Nutrition and Agriculture, 2010, 2, 105-109. http://dx.doi.org/10.2174/2212798411002020105 4. I. Tomaz, L. Maslov, D. Stupic, D. Preiner, D. Asperger, J. Karoglan Kontic, Phytochemical Analysis, 2015, 27, 13-22. http://dx.doi.org/10.1002/pca.2582 5. C. Carrera, A. Ruiz-Rodriguez, M. Palma,C. G. Barroso, Analytica Chimica Acta, 2012, 732, 100-104. http://dx.doi.org/10.1016Zj.aca.2011.11.032 6. A. Liazid, R. F. Guerrero, E. Cantos, M. Palma,C. G. Barroso, Food Chemistry, 2011, 124, 1238-1243. http://dx.doi.org/10.1016/j.foodchem.2010.07.053 7. Z. Ju,L. R. Howard, Journal of Food Science, 2005, 70, S270-S276. http://dx.doi.Org/10.1111/j.1365-2621.2005.tb07202.x 8. P. Mazzuca, P. Ferranti, G. Picariello, L. Chianese, F. Addeo, Journal of Mass Spectrometry, 2005, 40, 83-90. http://dx.doi.org/10.1002/jms.778 9. I. Revilla, S. Perez-Magarino, M. L. Gonzalez-SanJose,S. Beltran, Journal of Chromatography A, 1999, 847, 83-90. http://dx.doi.org/10.1016/S0021-9673(99)00256-3 10. J. Cacho, P. Fernandez, V. Ferreira, J. E. Castells, American journal of enology and viticulture, 1992, 43, 244-248. 11. G. Mazza, L. Fukumoto, P. Delaquis, B. Girard, B. Ewert, Journal of Agricultural and Food Chemistry, 1999, 47, 4009-4017. http://dx.doi.org/10.1021/jf990449f 12. D. Favretto,R. Flamini, American Journal of Enology and Viticulture, 2000, 51, 55-64. 13. R. R. Montealegre, R. R. Peces, J. L. C. Vozmediano, J. M. Gascuena,E. G. Romero, Journal of Food Composition and Analysis, 2006, 19, 687-693. http://dx.doi.org/10.1016/jjfca.2005.05.003 14. S. Gomez-Alonso, E. Garcia-Romero,I. Hermosin-Gutier-rez, Journal of Food Composition and Analysis, 2007, 20, 618-626. http://dx.doi.org/10.1016/jjfca.2007.03.002 15. P. Iacopini, M. Baldi, P. Storchi, L. Sebastiani, Journal of Food Composition and Analysis, 2008, 21, 589-598. http://dx.doi.org/10.1016/jjfca.2008.03.011 16. B. Lapornik, M. Prosek, A. G. Wondra, Journal of Food Engineering, 2005, 71, 214-222. http://dx.doi.org/10.1016/jjfoodeng.2004.10.036 Tomaz et al.: Solid-liquid Extraction of Phenolics ... Acta Chim. Slov. 2016, 63, 287-297 297 17. B. Lorrain, I. Ky, L. Pechamat, P. L. Teissedre, Molecules, 2013, 18, 1076-1100. http://dx.doi.org/10.3390/molecules18011076 18. V. Ivanova, M. Stefova, B. Vojnoski, A. Dornyei, L. Mark, V. Dimovska, T. Stafilov, F. Kilar, Food Research International, 2011, 44, 2851-2860. http://dx.doi.org/10.1016/j.foodres.2011.06.046 19. Z. M. Jin, J. J. He, H. Q. Bi, X. Y. Cui, C. Q. Duan, Molecules, 2009, 14, 4922-4935. http://dx.doi.org/10.3390/molecules14124922 20. R. Tsao,R. Yang, Journal of Chromatography A, 2003, 1018, 29-40. http://dx.doi.org/10.1016Zj.chroma.2003.08.034 21. R. Flamini, D. Tomasi, Vitis, 2000, 39, 79-81. 22. J. E. Cacace, G. Mazza, Journal of Food Engineering, 2003, 59, 379-389. http://dx.doi.org/10.1016/S0260-8774(02)00497-1 23. S. L. C. Ferreira, R. E. Bruns, H. S. Ferreira, G. D. Matos, J. M. David, G. C. Brandao, E. G. P. da Silva, L. A. Portugal, P. S. Reis, A. S. Souza, W. N. L. dos Santos, Analytica Chimica Acta, 2007, 597, 179-186. http://dx.doi.org/10.1016/j.aca.2007.07.011 24. M. A. Bezerra, R. E. Santelli, E. P. Oliveira, L. S. Villar, L. A. Escaleira, Talanta, 2008, 76, 965-977. http://dx.doi.Org/10.1016/j.talanta.2008.05.019 25. I. Tomaz, L. Maslov, Food Analytical Methods, 2016, 9, 401-410. http://dx.doi.org/10.1007/s12161-015-0206-7 26. J. Karoglan Kontic, I. Rendulic Jelusic, I. Tomaz, D. Preiner, Z. Markovic, D. Stupic, Z. Andabaka, E. Maletic, International Journal of Food Properties, 2016, 19, 1806-1824. 27. S. Z. Mikhail, W. R. Kimel, Journal of Chememical & Engeenering Data 1961, 6, 533-537. http://dx.doi.org/10.1021/je60011a015 28. I. S. Khattab, F. Bandarkar, M. A. A. Fakhree, A. Jouyban, Korean Journal of Chemical Engineering, 2012, 29, 812817. http://dx.doi.org/10.1007/s11814-011-0239-6 29. J. Bakker, C. F. Timberlake, Journal of the Science of Food and Agriculture, 1985, 36, 1315-1324. http://dx.doi.org/10.1002/jsfa.2740361217 30. M. Pinelo, A. Arnous, A. S. Meyer, Trends in Food Science & Technology, 2006, 17, 579-590. http://dx.doi.org/10.1016Zj.tifs.2006.05.003 31. B. A. Acosta-Estrada, J. A. Gutierrez-Uribe, S. O. Serna-Sal-divar, Food Chemistry, 2014, 152, 46-55. http://dx.doi.org/10.1016/j.foodchem.2013.11.093 Povzetek Sestava in koncentracija flavonoidov sta pomembna za karakterizacijo grozdnih sort, saj te spojine vplivajo na kakovost grozdja in vina. Razvili smo novo ekstrakcijsko metodo za pridobivanje flavonoidov, npr. antocianinov, flavonolov in flavan-3-olov iz grozdnih kožic. Optimizacijo ekstrakcije flavonoidov tekoce-trdno smo izvajali z uporabo modeliranja odzivne površine (RSM) ob upoštevanju tipa organskega topila in njegovega deleža, kakor tudi temperature in casa ekstrakcije. Optimalni pogoji so bili ekstrakcijsko topilo acetonitril:voda:mravljicna kislina (20:79:1; v/v/v), temperatura ekstrakcije 50 °C in cas ekstrakcije 1 h, ekstrakcija v enem koraku z razmerjem med trdnim vzorcem in topilom 1:80 g mL-1 (125 mg grozdnih kožic v prahu in 10 mL ekstrakcijskega topila). Nova optimalna ekstrakcijska metoda je poceni, preprosta, hitra, tocna in selektivna za ekstrakcijo preprostih flavonoidov. Tomaz et al.: Solid-liquid Extraction of Phenolics 298 Acta Chim. Slov. 2016, 63, 298-308 DOI: 10.17344/acsi.2016.2232 Scientific paper Study of the Influence of Key Process Parameters on Furfural Production Ljudmila Fele @ilnik,*'1 Viktor Grilc,1 Ivan Mirt2 and @eljko Cerove~ki2 1 National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, 2 Tanin Sevnica d.d., Hermanova 1, SI-8290 Sevnica * Corresponding author: E-mail: ljudmila.fele@ki.si Tel: +386 1 4760 220; fax: +386j 1 4760 300. Received: 05-01-2016 Abstract The present work reports the influence of key process variables on the furfural formation from leached chestnut-wood chips in a pressurized reactor. Effect of temperature, pressure, type and concentration of the catalyst solution, the steam flow rate or stripping module, the moisture content of the wood particles and geometric characteristics such as size and type of the reactor, particle size and bed height were considered systematically. One stage process was only taken into consideration. Lab-scale and pilot-scale studies were performed. The results of the non-catalysed laboratory experiments were compared with an actual non-catalysed (auto-catalysed) industrial process and with experiments on the pilot scale, the latter with 28% higher furfural yield compared to the others. Application of sulphuric acid as catalyst, in an amount of 0.03-0.05 g (H2SO4 100%)/g d.m. (dry material), enables a higher production of furfural at lower temperature and pressure of steam in a shorter reaction time. Pilot scale catalysed experiments have revealed very good performance for furfural formation under less severe operating conditions, with a maximum furfural yield as much as 88% of the theoretical value. Keywords: Furfural production, chestnut woodchips, process variables, acid catalysed process 1. Introduction Interest in the production of bio-chemicals and biofuels from renewable resources has vastly increased in the last decade, mainly as a result of the limited availability of petroleum reserves and to reach the goals of Paris 2015 Agreement. Biomass residues represent a potential source for production of chemicals such as alcohols, sugars, phenolic fractions, furfural, lower organic acids, etc. There is an ongoing challenge to develop economically-efficient and environmentally-benign technologies to transform lignocellulosic biomass into fuels1 and chemicals.2 Furfural, derived from hemicelluloses that are composed mainly of pentoses (C5 carbohydrates), is an extremely important intermediate for high value-added products, especially for the synthesis of furan derivatives, solvents for a broad range of applications, fungicides, insecticides, resins etc. Recently, an increased interest has arisen to upgrade furfural to furan-based biofuels or fuel additives, chemical intermediates and bio-solvents that are less toxic; correspondingly the value of furfural has increased. Furfural is almost exclusively produced by hydrolysis of pentosanes from plant residues to pentoses, followed by the dehydration reaction to furfural, since no competitive commercial synthetic route exists.3-4The mechanism of the furfural formation from the lignocellulosic material is relatively well defined, but very little information about kinetics of these heterogeneous reactions is known. The majority of the authors considered the hydrolysis reaction of the hemicellulose with respect to the cleavage mechanism of the glycosides bond as pseudo-homogeneous reaction. Pseudo kinetic model was proposed, mainly as a result of non-uniform polymer characteristics of hemicellulose and partly unexplained parallel reactions and consecutive degradation reactions of furfural. Furfural is formed from pentosanes by two consecutive reactions, namely hydrolysis of the pentosane-chain into pentoses and their dehydration via intermediates to furfural.5Both reactions take place in solid and liquid phase, but the mass transfer occurs also in the vapor phase. Abatzoglou et al.6 in their work on acid catalysed hydrolysis of sawdust, suspended in dilute solution of mineral acid in a continuous plug flow reactor, sug- Zilnik et al.: Study of the Influence of Key Process Parameters Acta Chim. Slov. 2016, 63, 298-308 299 gested the use of a simple empirical pseudo-kinetic model, without taking into account the formation and disappearance of intermediates. The cleavage of the glycoside bond and sugar formation was described by several authors7-8 and discussed by Agirrezabal-Telleria et al.9 and has been carried out in several subsequent steps, using steam or dilute acid pretreatment. The hydrolysis of pentosane to pentose starts with protonation of the ether oxygen link to form a trivalent oxygen, followed by a cleavage of the oxygen bond to give the carbonium ion on one side and a hydroxyl group on the other side, reaction of the carbonium ion with water, liberation of H+ ion and the OH-group formation. Antal et al.10 examined the furfural formation mechanism from D-xylose in water with and without catalyst. Two alternative hypotheses were studied; the first one suggested the consecutive reactions via intermediates with open rings and the other one the acid catalysed consecutive reactions with intermediate 2, 5-anhydride. The latter model was more consistent with experimental data. The mechanism of pentose cyclodehydration to furfural by two subsequent 1, 2-eliminations and 1, 4-elimination was presented8 and discussed as the main mechanism reported for Broensted acid catalysed cyclodehydration process. A very recent review of the literature9 shows increased activities in studying the dehydration reactions of sugars promoted by (homogeneous) acid catalysts such as formic, acetic, sulphuric and phosphoric acid, using the combined mineral acids and salts as catalysts, as well as by heterogeneous acid catalysts. Among homogeneous catalysts sulphuric acid is the most commonly used in the industrial production of furfural.11-12 Recent research on furfural formation and production, searching for novel catalytic systems based on Lewis acid sites13 has indicated the difference in the reaction pathways of Broensted acid catalysed xylose dehydration to Lewis/Broensted acid catalysed process. The authors suggested that using the combined Lewis and Broensted acids, xylose isomerization (Lewis acid catalysed) to xylulose and subsequent dehydration (Broensted acid catalysed) dominates over the direct con- version of xylose to furfural, catalysed only by the Broensted acid. The synergistic effect between Lewis acid catalysts and concentrated carboxylic acid (weak Broensted acidity) solutions towards the furfural formation from xylose was observed.14 According to recent studies the Lewis/Broensted acid site ratio directly affects the dehydration rate and the furfural yield. Lewis acid sites accelerate the xylose conversion rate as compared to Broensted sites, whereas the presence of Broensted site is required to achieve a significant furfural yield improvement. The first reaction step of furfural formation from pen-tosanes is therefore auto-catalysed hydrolysis towards mono-sugar production, which proceeds rapidly, while the second step, namely the dehydration, is much slower and therefore a considerable loss of furfural occurs through side reactions, such as degradation and condensation. As a consequence, much lower yield of furfural is achieved in its production process as compared to theoretically attainable one. The average pentosan contents of some raw materials, theoretical furfural yields and yields in industrial processes are given in Table 1. It can be noticed that only around 55-60% of the potential furfural yield, determined according to AOAC method, can be exploited in non-catalysed industrial processes, which accounts for around 30% of available pentosans in the raw material. Stoichometricaly, following both reactions,9 the theoretical furfural weight-basis yield from pentosan is 72.7% and 64% from pentose. The dehydration reaction, when catalysed by other catalyst than acetic acid, may be appropriately tuned to improve furfural yield and make the process more efficient.15 The prompt removal of furfural from the reactor is of crucial importance as well, therefore a stripping agent such as steam or nitrogen is used, or an appropriate extraction process can be employed. 1. 1. Aim of the Work In the chemical processing plant at Tanin Sevnica chemical company http://www.tanin.si/ (Figure 1), furfur- Table 1. Pentosan content of raw materials, theoretical furfural yields and yields in industrial processes.16,3 Raw materials Pentosan content Theoretical* Furfural yields in % furfural yield % industrial processes % Corncobs 30-32 23.4 10 Oats husks 40 22.4 10 Cotton husks 23-28 18.6 8-9 Bagasse 25-27 17.4 8-9 Birch wood+ 25 18.0 7-8 Chestnut wood+ 16.7 11.2 5-6 Oak wood+ 20-21 11.7 5-6 Olive cake 21-23 16.6 5-6 Rice husk 16-18 - 6 Sunflower hull - - 8-9 *- according to Association of Agricultural Chemists (AOAC); + - leached wood chips after tannin extraction Zilnik et al.: Study of the Influence of Key Process Parameters ... 300 Acta Chim. Slov. 2016, 63, 298-308 al, acetic acid and methanol are produced from leached chestnut wood chips through the hydrothermal auto-catalysed process using steam as a hydrolyzing, stripping and separating agent. From the raw material point of view, the process operates in a batch manner, with two reactors in sequence. About 3500 kgdrymatter/h of leached wood chips enters the furfural production plant shown in Figure 1. In the present work, the research aiming at hydrothermal process optimization of the furfural production was carried out, with the main purpose to systematically determine and examine closely the key process (thermodynamic, operating) parameters that influence the furfural yield, primarily on the laboratory scale. The findings from bench-scale experiments were subsequently used as a starting point to plan the development work on the pilot plant and semi-industrial scale production plant. Non-catalysed and catalysed processes were considered. 2. Materials and Methods For this study a batch of leached chestnut wood chips was received, sampled from the material employed in the industrial process, with the pentosan content of 17-19%dm (on the dry basis) and average moisture content between 40 and 45%. The material was stored in the cold room at temperature of 5 °C, while smaller amounts of the material for daily needs were held in the fridge. Before each experiment, the characterization of the raw material was performed, namely the particle size distribution, bed bulk density and average moisture content of the material. The measured bed bulk density varied between 0.26 g/mL up to 0.34 g/mL. In our experiments, the leached chestnut wood chips with two different moisture contents of approx. 30% and 43% were used. The major part (80 wt.%) of the particles were of the size between 2.0 mm and 11.2 mm. Due to clogging problems in preliminary experiments, a decision was made to use sieved material without fine fraction (particles below 2 mm) in our catalytic experiments. As a catalyst, sulphuric acid of different concentrations (3.7%, 38.5% and 90%) in an amount of 0.03-0.05 g H2SO4/g d.m. (dry material) was applied. Catalyst application on the particles was made by wet impregnation and spraying methods, the former when dilute sulphuric acid was used as a catalyst. Sulphuric acid p.a. (concentration of 95-97%, density of 1.84 kg/L) was diluted in demineralized water to prepare solutions of different concentrations. Demineralized water was utilized to produce process steam for the reaction. 2. 1. Analytical Methods Weighing of leached chestnut wood chips and cel-lolignin was carried out using two laboratory balances of Figure 1. Process scheme of the industrial non-catalysed furfural production plant. Legend: PPR - press, M - mixer for catalyst application onto the wood particles (in preparation), S - silo, E1 and E2 - elevators, PTR1, PTR2, PTR3 and PTR4 - conveyors, D1, D2, D3 - reaction vessels, P1, P2 - pumps, CL - cooling line, RK - reservoir for reaction condensate, LC -steam condensate remover, FIT - steam flow rate indicator and transmitter, PI - pressure indicator, PIT - pressure indicator and transmitter, PT -pressure transmitter, tT - time transmitter, TI - temperature indicator, TIT - temperature indicator and transmitter. Žilnik et al.: Study of the Influence of Key Process Parameters ... Acta Chim. Slov. 2016, 63, 298-308 301 appropriate accuracies. Analytical balance Mettler® AT 261 with an accuracy of ± 0.1/0.01 mg and maximum load of 205 g was employed for analytical purposes. Before each experiment, the particle size analysis was performed on a Fritch® Pulverisette model 301.0 using standard sieves Retsch® of sizes 16.00, 11.20, 6.30, 3.15, 2.00 and 1.00 mm, according to the standard DIN-ISO 3310/1. 100 g of homogeneously mixed material was taken for the particle size analysis. After 10 min of material shaking, the fractions were weighed and the moisture content of each fraction was determined by means of the moisture analyzer Mettler® PM 460 with an accuracy of ± 0.01 g for mass and of ± 0.01% for moisture and maximum load of 410 g. Average weight percent of the fraction size and their moisture content were calculated. In every experiment, the characterization of each stream of the wood material (chips), entering or leaving the process (cellolignin residue), was carried out. Average moisture content of the material was determined also after the catalyst application on the leached chestnut wood particles. Gas chromatography was used to analyze the composition of the outlet flow from the reactor. The stream from the reactor consisted of furfural, ethanoic acid, methanol and 5-methyl-furfural dissolved in water. Analysis were performed on GC Carlo Erba® model 8130, equipped with flame ionization detector, using HP-FFAP capillary column of the length of 50 m, 0.32 mm ID with 0.52 pm film thickness to achieve the separation. The column was filled with Carbowax 20 M, covered with polyethylene glycol polar phase modified by nitrotherephtalic acid. Oven temperature was held at 150 °C, the injector and detector temperatures were 220 °C and 200 °C, respectively. Hydrogen served as a carrier gas with a flowrate of 1.5 mL/min. For the quantification of compounds in the samples an internal standard (IS) method was used, with propionic acid as IS. The samples were filtered through 0.25 pm filter prior the injection. When catalysed experiments were performed, the amount of acid applied on the leached wood particles was determined and controlled by potentiometric titration on pH-meter ISKRA® MA 5740. 2. 2. Furfural Formation Series of experiments, non-catalysed and catalysed, were carried out first on the laboratory scale and later on the pilot scale to examine the influence of key parameters such as: temperature, pressure, type of catalyst solution used and its concentration, the steam flow rate (measured through the amount of its cumulative condensate, represented by the stripping module Sm (ml/g( dry.matter h)), the moisture content of the leached chestnut-wood particles and geometric characteristics (size and type of the reactor, mean particle size, bed height). One stage process was considered, meaning that reactions, hydrolysis and dehydration are taking place in the same apparatus. 2. 2. 1. Laboratory Experimental Setup and Procedure Experiments were first carried out on the laboratory apparatus, shown in Figure 2, consisted of the pressure reactor Ernst Haage® type 1220, constructed of Cr-Ni-Mo steel, of 2 L volume (D = 10 cm, H = 27 cm), with operating temperature up to 350 °C and pressure up to 325 bars. The reactor was heated by an electric heating coil mounted in a double insulation jacket of the reactor. The temperature was measured in the middle of the reactor by thermocouple wire Fe-CuNi (Constantan) and controlled by temperature controller. Additional thermocouple Dalmacija® (NiCr-Ni) with the operating range between -65.0 °C and 199.0 °C and accuracy of ± 0.1 °C was inserted in the reactor to measure the temperature. The pressure was measured by Bourdon tube pressure gauge with the measuring range of 0-16 bar and accuracy of ± 0.1 bar. Glass wool served as thermo-insulation of the reactor. Steam was produced in a stainless steel autoclave Andreas Hofer® with the following characteristics: Vnet = 50 L, D = 30 cm, H = 75 cm, T = 350 °C, P = 100 bar, Ph , = ' ' max ' max ' heating 18 kWel. Steam was fed to the reactor on a side of a reactor cover through the feeding line, which led to the lower one third of the reactor. To prevent the condensation of the steam in the line between the steam chamber and the reactor, electrical heating mantle was employed. Two needle valves were used to control the pressure in the reactor and steam flow at the exit of the reactor. The outlet flow was condensed and measured. Non-catalysed experiments were carried out to find out which parameters are playing the most important role Figure 2. Scheme of the laboratory apparatus used for hydrothermal processing of leached chestnut-wood chips. Legend: LR- reactor Ernst Haage 1220, RP - steam producer, LH -cooler, IV1, IV2, IV3- needle valves, VV - safety valve, EG1, EG2, EG3 - electric heater, U1, U2, U3 - switched-mode power supply, R1, R2 - temperature controller, PI - pressure indicator, TI - temperature indicator, TT - temperature transmitter, T - temperature display. Zilnik et al.: Study of the Influence of Key Process Parameters ... 302 Acta Chim. Slov. 2016, 63, 298-308 in the hydrothermal process and to compare the process conditions and furfural yields with the actual industrial process data from the company Tanin d.d., in spite of different geometry of the reactors. The reactor was loaded with 550 g of leached chestnut wood chips, regardless of the moisture content. A sample of the leached wood chips was taken for particle fraction size analysis and average moisture content determination. In non-catalysed experiments leached chestnut wood chips with both initial moisture contents (31% and 43%) were treated. In catalysed process only leached chestnut wood chips with average moisture content of 43% and without particles size fraction below 2.0 mm were used. The reactor was sealed and preheated by an electric heater up to 100 °C. The set temperature was reached in 13-20 minutes. Steam was introduced into the reactor with appropriate temperature and pressure and as soon as the operating T and P were reached in the reactor, the steam flow through the reactor was set to attain a pre-selected stripping module Sm (rate of stream load), defined as the volume of the outlet condensate flow (mL) per mass unit of dry wood in the reactor (g) in unit of time (h). The time to reach the operating temperature in the reactor was recorded and denoted as the beginning of the process (to). Non-catalysed experiments were carried out at temperatures between 180 °C and 190 °C, at pressures between 9-12 bar, initial liquid/solid (L/S) ratios of 0.39 and 0.76 g/g and stripping module between 1.0 and 1.3 mL/gdmh. In catalysed process, lower temperatures and pressures were applied, but higher initial L/S ratio between 1.5 and 1.8 g/g and higher stripping module, in the range between 1.3 and 4.0 mL/gd.m.h. Approximate the same load of the catalyst of different concentrations on the dry material was applied in all catalysed experiments. The duration of non-catalysed and catalysed process was 120 min and 100 min, respectively. Experiments at each of the process conditions were performed at least in triplicates. The first sample of the condensed outlet flow was taken 45 seconds after to, afterwards the sampling was carried out in intervals of 10 min, and only at the beginning of catalysed experiments 5 min interval was chosen. The samples were cooled down to room temperature and prepared for GC analysis. 2. 2. 2. Pilot Scale Setup and Procedure Based on the findings from the laboratory experiments, the pilot reactor of a column type was build up, with an effective volume of 10 L, 88 mm of diameter and 2 m of height. The reactor was heated by steam, which entered a double insulation jacket of the reactor. The reactor was designed in such a way, that both ends could be opened. The raw material (leached chestnut wood chips) entered the top of the reactor and formed a fixed bed, while the steam was introduced through a perforated distributor, mounted in the reactor at the bottom part. The valve for steam condensate at the bottom was slightly opened during the experimental run. The filter plate at the top of the bed prevented the particles to leave the reactor together with steam. The outlet steam flow from the top of the reactor entered a separator, where fine dusty particles were removed, followed by condensation in a heat exchanger and collected in a graduated vessel. The samples were taken every 10 min for GC analysis. 3. Results and Discussion 3. 1. Effect of Temperature, Pressure, Stripping Module and Moisture Content in Non-catalysed Lab-scale Experiments A series of non-catalysed experiments were performed at two temperatures and pressures, using the particles with initial average moisture contents of 31% and 43% and by a variation of stripping module Sm. The operating conditions and results of most representative non-catalysed laboratory experiments are presented in Table 2. Maximum concentration of furfural in the product stream was achieved 30-40 min after t0. It was found out that the initial moisture content of the particles in the concentration range studied did not have a significant effect on furfural yield of the process. Some differences in the dynamics of the furfural formation were noticed, but they could not be ascribed to the influence of the moisture content. The most important process parameters are temperature, pressure and stripping module. By lowering the tem- Table 2. Conditions and results of the non-catalysed laboratory experiments of leached chestnut wood chips in one-stage process.16 ^preheat min md.m. g Wm,p% L/S g/g Wm,c% T °C P bar Sm mL/g.h Cfmax% 13 383.9 30.2 0.43 50.7 190.1 11.6 1.28 3.77 5.2 15 396.0 28.0 0.39 40.8 181.1 8.8 1.24 2.67 3.7 18 396.0 28.0 0.39 28.0 190.6 11.8 0.94 3.74 4.1 15 312.4 43.2 0.76 53.9 191.1 11.9 1.35 3.92 5.1 tpreheat - preheating time, mdm - mass of dry material, wmp - average moisture content of the particles entering the process, L/S - liquid to solid ratio, wmc - average moisture content of cellolignin residue, Sm - stripping module, Cfmax - maximum concentration of furfural in the outlet flow, nf - furfural yield on the dry basis Žilnik et al.: Study of the Influence of Key Process Parameters ... Acta Chim. Slov. 2016, 63, 298-308 303 perature from 190 °C to 180 °C and pressure from 12 bar to 9 bar, using the same stripping module, the furfural yield has decreased for about 30% (see Table 2). In Figure 3a, the concentrations of furfural, ethanoic acid, methanol and 5-methyl furfural in the outlet stream from the reactor during non-catalysed experimental run on wood particles having 31.3% of moisture at 190 °C, 11.6 bar and stripping module of 1.3 mL/g.h are depicted. Furfural reached its maximum concentration in 40 min of hydrothermal process, at the same time the concentration of ethanoic acid increased from 0.5% up to 2%, in some experiments even up to 2.5% with its maximum concentration at the time near furfural maximum. The most volatile component methanol reached peak concentration of about 1% at the beginning, after that its concentration was decreasing. The concentration of byproduct 5-methyl furfural was quite low during the run, with the concentration between 0.1% and 0.2%. Using lower stripping module (e.g. 0.94 mL/g.h), i.e. at lower linear velocity of the steam passing through the bed of leached chestnut wood chips, the furfural yield was only around 3-4% on the dry material, which means that we have lost the furfural due to side reactions taking place in the reactor. The results from the laboratory experiments agreed fairly well with the actual non-catalysed industrial process. 3. 2. Effect of Catalyst Concentration, T, P and Stripping Module in Catalysed Lab-scale Experiments In the catalysed experiments, leached chestnut wood chips with an average moisture content of 43% without particle fraction size below 2.0 mm were used in order to avoid the issues connected with uniform distribution of sulphuric acid, which served as a catalyst. The acid applied to fine particles might also cause the destruction of cellolignin and problems with stuffed valves at the exit of the reactor. An amount of the catalyst regardless its concentration was always in the range 0.03-0.05 g H2SO4/g d.m. (dry material). The effect of catalyst concentration, temperature, pressure and strip- ping module on the furfural formation from pentosans and on furfural yield was studied. The operating conditions and results of most representative catalysed laboratory experiments with dilute (3.7%) sulphuric acid are presented in Table 3. The catalyst in an amount of 0.03 g H2SO4/g d.m. was applied by wet impregnation method, therefore the initial moisture content reached the value of 60% and the liquid/solid ratio in the reactor was around 1.5 g/g. The experiments were performed at two temperatures, namely at 170 °C and 180 °C and at various stripping modules (1.3, 2 and 3 mL/g.h). Preheating time from 100 °C up to the operating temperature was found to be very important, and it should not last too long, otherwise lower furfural yield due to side reactions is inevitable. The composition of the outlet flow from the reactor and the furfural yield achieved in the catalysed process for one run by dilute sulphuric acid is depicted in Figure 3b. The catalyst influenced the dynamics of the furfural formation; higher initial furfural concentration and its maximum concentration in 10-20 min after to were noticed. Higher stripping module enhanced the removal of furfural from the surface of the wood particles to the vapor phase and minimized the possibility for side reactions of furfural, such as degradation and condensation. Lower temperature (170 °C) is more favorable for furfural production compared to higher temperature (180 °C) at low stripping module (1.3 mL/g.h) due to lower extent of furfural side reactions. Lower pressure enables an enhanced diffusion of the reaction products such as furfural into the bulk steam phase. At higher steam flow rate, temperature in the range studied, did not influence the furfural yield significantly. Comparing the results with non-catalysed one, it can be noticed that dilute sulphuric acid enhanced the furfural formation at lower temperature and pressure, such as 170 °C and 7 bars. An increase of up to 45% in furfural yield was recorded when catalysed experiment instead of non-catalysed was performed at 180 °C and 8.5 bar at similar stripping module (1.3 mL/g.h). More pronounced effect on furfural yield can be reached by increasing the stripping module, as shown in Figure 4a. Linear dependency of furfural yield on stripping module is evident at 180 °C and 8.9 bars and from stripping mod- Table 3. Conditions and results of the catalysed (3.7% H2SO4 solution) laboratory experiments of leached chestnut wood chips in one-stage process.16 t min m. g w % w % L/S g/g w % T °C P bar S mL/g.h Cfmax% %% preheat_d.m. °_m,p_m,w_» »_ m,c_m_Z_ï_f 22 313.5 43.0 60.5 1.53 37.8 170.1 7.0 1.34 5.62 5.8 22 313.5 43.0 60.8 1.55 24.7 178.6 8.5 1.35 5.93 5.4 21 314.6 42.8 60.4 1.53 21.2 180.1 8.9 2.01 4.11 6.0 19 314.0 42.9 60.3 1.52 41.2 169.7 6.7 2.99 3.41 8.1 tpreheat - preheating time, mdm - mass of dry material, w - average moisture content of material before catalyst application, wm w - average moisture content of material after catalyst application, L/S- liquid to solid ratio, wmc - average moisture content of cellolignin residue, Sm - stripping module, Cfmax - maximum concentration of furfural in the outlet flow, nf - furfural yield on the dry basis Zilnik et al.: Study of the Influence of Key Process Parameters ... 304 Acta Chim. Slov. 2016, 63, 298-308 a) E 3 ■D £ O „ b) E TJ F O —ft— furfural —o— ethanoic acid —A— methanol —0— 5-m-furfural ^lurliir^l O*— O—G —O—D=-Ô—û—Û—Û—6—ô—Ô—Û —i— 20 —i— 40 —I— 60 —i— SO —r— 100 —I— 120 t (min) —*—furfural —o— ethanoic acid —A— methanol —O— 5-m-furfural ^lurfural / ' / / „* / x —* Ai O^&O-O-G-O—0—0^0=^=0_Q ô—ô—o—»—S —i— 20 —i— 40 —I— 60 —I-- 100 t (min) amount to be applied. The preheating time had to be shortened to prevent the unwanted side reactions of furfural. The effect of temperature, pressure and stripping module on the a) 8,5 -j 8.0- 7,5- £ 7,0 - ■o 6.5- o- 6,0 - 5,5- 5,0- A T=170I1CI P= 6,9 bar ----T=170°C, P= 6,9 bar, linear fit -«- T= 180°C, P= 8.9 bar b) t r а,o ■ 7,s. 7,0 - б,5 -6,0 ■ 5,5 • ¿if. y' X ' s S ' ■ ■ « if s Of 1,0 1,5 —I— 2,0 —I— 2,5 —I— 3,0 3,5 Sm(mL/g.h) O T= 150 C, P= 4 bar * T= 160°C, P= 5,5 bar V T= 170°C, P= 7,2 bar „ -&--- 0 \ s S v \ o Figure 3. The composition of the outlet flow from the reactor and the furfural yield in a) non-catalysed process (process conditions: wmp =31.3%, T = 190 °C, P = 11.6 bar, Sm = 1.3 mL/g.h) and b) catalysed process by dilute sulphuric acid (process conditions: wmp = 43.2%, wmw = 60%, T = 170 °C, P = 6.7 bar, Sm = 3 mL/g.h, 0.03 g H2SO4/g d.m. using 3.7% acid concentration). ule 2 mL/g.h onward, no significant difference in furfural yields between two measured process conditions is observed. By increasing the stripping module from 1.34 to 3.0 mL/g.h at 170 °C and 7 bar, catalysed by 3.7% sulphuric acid solution in an amount of 0.03 g H2SO4/g d.m., an increase of up to 40% in furfural yield can be gained, which represents around 70% of theoretically possible furfural yield. Catalytic experiments were carried out also with higher concentrations of sulphuric acid, namely with 38% and 90% solutions. In both cases spraying method was used to apply acid in an amount of 0.038 g H2SO4/g d.m. The initial moisture content has slightly (around 2%) increased when 38% solution was employed. An issue how to uniformly distribute the acid occurred during application of 90% sulphuric acid solution due to high viscosity and small 5.0 - 1,0 1,5 2,0 2,5 Sm(mL/g.h) 3,0 c) 7,5 1 7,0 - 6,5- e 6,0- gf ■c 5,5- C 5,0- 4,5- 4,0- ■ û- T= 140°C. P= 2,6 bar O- T= 150°C, P= 4 bar * T= 160°C, P= 5,3 bar *. 1,5 O" 2.0 2,5 3.0 3,5 Sm(mL/g.h) 4,0 4,5 Figure 4. Influence of temperature, pressure and stripping module on furfural yield in catalysed process using a) 3.7% sulphuric acid solution, b) 38% solution of sulphuric acid and c) 90% sulphuric acid solution; the curves are eye guidance. Žilnik et al.: Study of the Influence of Key Process Parameters ... Acta Chim. Slov. 2016, 63, 298-308 305 furfural yield was studied. Catalysed process with 38% sulphuric acid has shown best results at 160 °C. Temperature 170 °C had favorable effect on furfural formation from pentosans, with higher initial and maximal concentrations of furfural observed in the outlet stream from the reactor, but most likely the initial phase of furfural formation was missed; therefore as a result lower furfural yields were obtained. The influence of temperature, pressure and stripping module on furfural yield in the catalysed process by 38% sulphuric acid solution in the load of 0.038 g H2SO4/g d.m. is depicted in Figure 4b. It is clearly seen that increasing stripping module resulted in increased furfural yield up to a certain Sm, and then the drop in furfural yield is noticed, most probably due to condensation of the saturated steam in the reactor and increased liquid film around the particles and therefore increased resistance against the mass transfer to the vapor phase. In Figure 4c, influence of temperature, pressure and stripping module on furfural yield in the catalysed process by 90% sulphuric acid solution in a load of 0.037 g H2SO4/g d.m. is presented. Using concentrated sulphuric acid as a catalyst, the formation of furfural was accelerated at lower temperature and pressure, and due to furfural reactivity, side reactions were taking place. One of the reasons for lower furfural yield achieved, compared to lower concentrations of the acid, might also be its nonuniform distribution on wood particles. Laboratory experiments have shown that sulphuric acid is suitable as a catalyst, in an amount of 0.03-0.04 g H2SO4/g d.m., since it enables higher production of furfural at lower temperature and pressure of steam in shorter reaction time, with increased initial, maximal and instantaneous furfural concentrations. The best results were obtained in experimental runs with dilute sulphuric acid at 170 °C and 7 bar of steam pressure and stripping module of 3 mL/g.h. Using the lowest stripping module of 1.35 mL/g.h in catalysed process by dilute sulphuric acid at 170 °C (6.9 bar), approximate 12% higher furfural yield is obtained in comparison with non-catalysed process at 190 °C (11.6 bar). 3. 3. The Effect of Geometry of the Reactor Comparison was made between our results obtained on the laboratory scale (NIC), results from research work in Riga (IWC)17 and the data from the industrial process (Figure 1), shown in Table 4, with the indication of the geometric characteristic (H/D) of the reactors used for the production of furfural. We refer to the industrial process in Tanin Sevnica chemical company, where the data (per reactor) were obtained from an annual production data of the company (input and output). From Table 4 it can be seen, that there were big differences in geometry of reactors at NIC, IWC and on industrial site. Geometry of the reactor is one of very important parameters in the process. Decreasing the diameter of the reactor at constant volumetric flowrate of the steam, the Reynolds number for the steam passing through the reactor is increased and therefore the overall mass transfer coefficients from the liquid to the vapor phase are increased in effect. High H/D ratio of the reactor offered two advantages; namely, increased apparent linear velocity of the steam at its constant flowrate and augmented au-tocatalytic effect in the upper part of the chips bed, caused by released ethanoic acid from the lower part of the reactor. From the comparison of maximal values of linear velocities of the steam calculated on the void cross section of different reactors it can be seen, that linear velocities of steam in experimental runs at NIC were much lower with regard to those at IWC and on industrial site. Therefore, it can be concluded that lower furfural yields were reached in laboratory experiments due to lower linear velocity of the steam and lesser autocatalytic effect caused by the released ethanoic acid. Table 4. Comparison of operating parameters and results for few non-catalysed and catalysed experiments carried out at NIC, IWC and industrial production data. Lab reactor NIC, H/D = 2.6 md.m. kg_Wm,p% Ccat% Cijn% T °C p bar Sm mL/g.h v,in m/s f 0.312 43.2 / / 190 12 1.3 0.0020 5.1 0.314 42.9 3.7 3.0 170 7.0 3.0 0.0067 8.1 0.314 43.0 90.0 4.3 162 5.5 4.1 0.0154 7.2 Lab reactor IWC, H/D = 25.6, superheated steam 1.427 565 / / 180 9 4.0 0.0828 5T 1.440 58.5 75 3 160 5 2.8 0.1003 7.8 1.487 46.5 25 3 165 6 2.9 0.0871 9.4 Industrial reactor*, H/D = 6.2, superheated steam 3400 42-45 / / 195 9 13 0.1036 51" mdm - mass of dry material, wm p - average moisture content of material before catalyst application, Ccat - concentration of H2SO4 solution, Cd m. -an amount of the catalyst on the dry material, Sm - stripping module, vlin - average linear steam velocity, nf - furfural yield on the dry basis,* -stage-wise process (2 reactors in operation) Zilnik et al.: Study of the Influence of Key Process Parameters ... 306 Acta Chim. Slov. 2016, 63, 298-308 3. 4. Pilot scale Performance A series of non-catalysed and catalysed experimental runs were performed systematically on the pilot scale, varying the parameters such as temperature and pressure, the fraction size of the particles used (only in non-catalysed experiments), stripping module, the bed height, the concentration of the catalyst used and the catalyst load. Some results from those experiments are presented in Table 5. maximum yield, between 50% and 65%, reported by Montane et al.11 Using 98% sulphuric acid, special attention had to be paid to achieve the uniform distribution of the acid on the wood particles. Pilot scale, non-catalysed and catalysed experiments were both very successful in producing furfural in comparison to laboratory experiments and industrial runs. Furfural yield obtained by non-catalysed process on pilot Table 5. Operating conditions and results for some non-catalysed and catalysed pilot experiments. md.m. kg Wm,p% C .% cat Pilot reactor, H/D Cd.m.% = 22.5 T °C P bar Sm mL/g.h nf% 1.891 35.2 / / 189.5 12.0 0.95 5.0 1.410 43.2 / / 190 12.0 1.67 7.1 1.489 50.61 / / 196 12.0 1.7 7.5 1.505 44.53 32.1 2.2 176 8.0 1.82 7.0 1.553 39.60 31.2 2.1 163 5.4 3.0 8.3 1.410 46.75 33 5 166 6.0 3.99 9.9 1.598 48.47 98 2 166 5.7 2.1 8.8 mdm - mass of dry material, wm p - average moisture content of material before catalyst application, Ccat - concentration of H2SO4 solution, Cdm -an amount of the catalyst on the dry material, Sm - stripping module, nf - furfural yield on dry basis It was established that bed, composed of particle fraction size below 1 mm, could drastically (for 50%) reduce furfural yield compared to the bed composed of particles with size fraction between 6.3 mm and 11.2 mm. Using different bed heights it was found out that bed height did not have any significant effect on furfural yield, in the dimension studied at one-stage contact. The study on the stripping module at non-catalysed process on non-sieved particles has shown that at low stripping module such as 0.95 mL/g.h around 30% lower furfural yield (4.98%) is achieved compared to stripping module of 1.67 mL/g.h (7.10). Looking at the results of non-catalysed experiments at similar operating conditions on the laboratory scale (Table 2) and on the pilot scale (Table 4), 28% higher furfural yield is noticed on the pilot scale due to higher linear velocity of the steam achieved and faster furfural removal from the reactor. In catalysed experiments, sulphuric acid solution of 33% and 98% was used as a catalyst in an amount of 0.02-0.05 g H2SO4/g d.m. The catalyst reduces the activation energy for the reaction of furfural formation, therefore lower temperatures and pressures can be applied. Since the reactions of furfural formation as well as side reactions proceed faster, higher stripping modules are needed to avoid side reactions and furfural losses. The application of 0.05 g H2SO4/g d.m. of 33% sulphuric acid solution on the particles can give at 166 °C and 6 bars and high stripping module (3.99 mL/g.h) as high as 9.9% furfural yield, which corresponds to 88% of theoretically possible one. The yield is much higher with regard to the scale was 7.1% on the dry matter at quite low stripping module of 1.67 mL/gdmh, which represents 30% more compared to the yield from industrial stage-wise process and around 61% of the theoretically attainable. In catalysed experiments up to 40% to 60% higher furfural yields under less severe operating conditions (temperature, pressure) can be achieved compared to non-catalysed process. 4. Conclusions Both, laboratory and pilot scale experiments have revealed the most important process parameters that influence the furfural formation, namely temperature, pressure, concentration and amount of the catalyst, furfural removal rate, preheating time, geometry of the reactor and wood particles' fraction size. Higher temperature and pressure increase the furfural production rate in a one-stage non-catalysed process. Higher stripping module related to apparent linear velocity of the steam leads to a rapid removal of furfural (short residence time), thus preventing the un-desired side reactions and furfural loss. In a catalysed process, a comparably lower temperature and pressure could be used to achieve even as high as 40-60% increase in furfural yield compared to a non-catalysed process. Lower pressure enables an enhanced diffusion of the reaction products such as furfural into the bulk steam phase. The pilot scale experiments confirmed the importance of the geometry of the reactor in obtaining the best performance of the furfural production process due to increased Žilnik et al.: Study of the Influence of Key Process Parameters ... Acta Chim. Slov. 2016, 63, 298-308 307 apparent linear velocity of the steam and augmented auto-catalytic effect in the upper part of the chips bed. The experiments have shown the particle fraction size of wood chips had an important impact on the furfural yield, especially when the process was catalysed. Since the residue after digestion is used to complement the energy requirements of the overall process, the use of sulphuric acid as a catalyst might not be an optimal solution due to the challenges related to the consequent incineration of the processed cellolignin material and other environmental issues (SO3 in the exhaust gas). Therefore, other more suitable and more efficient catalysts are required, such as catalysts possessing Lewis/Broensted acid sites to directly impact the dehydration rate and the furfural yield with selectivity towards furfural production. 5. Acknowledgements The research work was financed by ARRS, Slovenian Research Agency (No. 3411-97-22-8693) and Tanin Sevnica chemical company, therefore their financial support is gratefully acknowledged. 6. Conflict of Interest Statement The authors have declared no conflict of interest. 7. References 1. Y. Sun, J. Cheng, Bioresour. Technol. 2002, 83, 1-11. http://dx.doi.org/10.1016/S0960-8524(01)00212-7 2. T. Werpy, G. Petersen, Top Value Added Chemicals from Biomass Volume I- Results of the Screening for Potential Candidates from Sugars and Synthesis Gas. NREL/TP-510-35523; National Renewable Energy Laboratory (NREL), 2014. 3. H. D. Mansilla, J. Baeza, S. Urzua, G. Maturana, J. Villa-senor, N. Duran, Bioresour. Technol. 1998, 66, 189-193. http://dx.doi.org/10.1016/S0960-8524(98)00088-1 4. N. Vedernikov, New approach in furfural production from pulping waste liquor: Proc. 8th. Intern. Symp. Wood Pulping Chem., Helsinki, Finland, 1995, 367-370. 5. W. Jeaggle, Integrated Production of Furfural and Acetic Acid from Fibrous Residues in a Continuous Process. Escher Wyss News 2, 1975, pp.1-15. 6. N. Abatzoglou, P. G. Koeberle, E. Chornet, R. P. Overend, E. G. Koukios, Can. J. Chem. Eng. 1990, 68, 627-638. http://dx.doi.org/10.1002/cjce.5450680414 7. D. Fengel, G. Wegener, Wood: chemistry, ultrastructure, reactions, Walter de Gruyter & Co., Berlin, Germany, 1989. 8. A. S. Mamman, J. M. Lee, Y. C. Kim, I. T. Hwang, N. J. Park, Y. K. Hwang, J. S. Chang, J. S., Hwang, Biofuels Bioprod. Biorefin. 2008, 2, 438-454. http://dx.doi.org/10.1002/bbb.95 9. Agirrezabal-Telleria, I. Gandarias, P.L. Arias, Catal. Today 2014, 234, 42-58. http://dx.doi.org/10.1016/j.cattod.2013.11.027 10. M. J. Antal, T. Leesomboon, W. S. Mok, G. N. Richards, Carbohydr. Res. 1991, 217, 71-85. http://dx.doi.org/10.1016/0008-6215(91)84118-X 11. D. Montane, J. Salvado, C. Torras, X. Farriol, Biomass Bioenergy 2002, 22, 295-304. http://dx.doi.org/10.1016/S0961-9534(02)00007-7 12. F. A. Riera, R. Alvarez, J. Coca, J. Chem. Technol. Biotech-nol. 1991, 50, 149-155. http://dx.doi.org/10.1002/jctb.280500202 13. V. Choudhary, S. I. Sandler, D. G. Vlachos, ACS Catal. 2012, 2, 2022-2028. http://dx.doi.org/10.1021/cs300265d 14. A. C. Doiseau, F. Rataboul, L. Burel, N. Essayem, Catal. Today 2014, 226, 176-184. http://dx.doi.org/10.1016Zj.cattod.2013.10.034 15. N. A. Vedernikov, S. S. Popov, A. Butsene, I. K. Kruma, V. N. Zakharov, D. V. Baldezens, Khim. Drev. 1993, 6, 53-59. 16. M. Nemanic, Študij procesa digestije prešanega izluženca kostanjevega lesa. Diplomsko delo, Fakulteta za kemijo in kemijsko tehnologijo, Univerza v Ljubljani, Ljubljana, 1997. 17. A. Y. Kalninsh, N.A. Vedernikov, Utilization of Harwood as a Chemical Raw Material in Latvian SSR: Appl. Polym. Symp. 1975, 28, 125-130. Zilnik et al.: Study of the Influence of Key Process Parameters ... 308 Acta Chim. Slov. 2016, 63, 298-308 Povzetek Predstavljeno delo obravnava vpliv ključnih procesnih spremenljivk na nastanek furfurala pri digestiji prešanega izluženca kostanjevega lesa v tlačnem reaktorju. Sistematično smo študirali vpliv temperature, tlaka, vrste in koncentracije raztopine katalizatorja, pretoka pare oz. »stripping« modula (hitrost odstranjevanja nastalih hlapnih produktov), vsebnosti vlage v lesnih delcih ter vpliv geometrijskih karakteristik kot so oblika in velikost reaktorja, velikost sekancev in višina sloja. Obravnavali smo le enostopenjski proces, eksperimentalno študijo pa smo izvajali v laboratorijskem in pilotnem merilu. Rezultate nekataliziranih laboratorijskih poizkusov smo primerjali z nekataliziranim (avto-kataliziran-im) industrijskim procesom in z rezultati eksperimentov, ki so bili izvedeni v pilotnem merilu. V slednjih so bili dobitki furfurala za 28 % višji glede na preostale poizkuse. Uporaba žveplove (VI) kisline kot katalizatorja v nanosu 0,03-0,05 g H2SO4 100 %/g s.s., omogoča pri nižji temperaturi in tlaku pare doseči večje dobitke furfurala v krajšem reakcijskem času. Katalizirani poizkusi nastanka furfurala v pilotnem merilu so se izkazali kot zelo učinkoviti, saj potekajo pod manj ostrimi pogoji z maksimalnim dobitkom furfurala , ki predstavlja 88 % teoretično možne vrednosti. Žilnik et al.: Study of the Influence of Key Process Parameters ... DOI: 10.17344/acsi.2016.2236 Acta Chim. Slov. 2016, 63, 309-316 309 Scientific paper H3PW12O40 Encapsulation by Nanoporous Metal Organic Framework HKUST-1: Synthesis, Characterization, Activity and Stability Ezzat Rafiee1'2'* and Narges Nobakht2 1 Department of Inorganic Chemistry, Faculty of Chemistry, Razi University, Kermanshah, 67149, Iran 2 Institute of Nano Science and NanoTechnology, Razi University, Kermanshah, 67149, Iran * Corresponding author: E-mail: ezzat_rafiee@yahoo.com Tel/fax: +98-833-427-4559 Received: 08-01-2016 Abstract Hybrid composite material was obtained through encapsulation of H3PW12O40 (PW) into HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylic acid), in molar composition of 5 Cu(NO3)2 • 3H2O /2.8 BTC/ 0.3 PW/ 0.6 CTAB by adding solutions of PW and copper salts to mixture of BTC and surfactant. The catalyst was characterized by various techniques including powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), laser particle size analyzer, Brunauer Emmett-Teller (BET). The acidity of the catalyst was measured by a potentiometric titration with n-butylamine and PW/HKUST-1 presented very strong acidic sites with Ei > 100 mV. This nano catalyst was successfully used for the synthesis of various P-keto enol ethers at 45 °C with 51-98% yield after 5-75 min. The catalyst was easily recycled and reused at least four times without significant loss of its activity (94% yield after forth run). The presence of the PW in PW/HKUST-1 and reused PW/HKUST-1 structure, eliminating any doubt about collapse of the HKUST-1 after catalytic reaction and can be followed by FT-IR, XRD and SEM techniques. Bronsted and Lewis acidity of the PW/HKUST-1 catalyst was distinguished by studying the FT-IR and determined by chemisorption of pyridine. The strength and dispersion of the protons on PW/HKUST-1 was considerably high and active surface protons became more available for reactant. Keywords: Heteropoly acid; Metal-organic framework; P-Keto enol ethers; Heterogeneous catalysts; Hybrid composite material. 1. Introduction In the last decade, metal organic frameworks (MOF-s) as one of the most important families of materials, constructed from metal containing nodes and organic linkers, has been considered as in several applications such as gas storage/separation and catalysis.1-4 The crystalline, porous structure in combination with huge surface area and pore volumes results in unique properties of these materials such as large porosity, high surface area, open metal centers, abundant aromatic ligands and ease of synthe-sis2,5-10 Up to now, several reactions have been carried out using MOFs as solid Lewis acid catalysts or catalyst supports but MOF materials usually do not possess Bronsted acidity, therefore some attempts have been made to introduce such functionality into them.11 Recently, the use of conventional nano-metal functionality in combination with acidic supports such as Al2O3 and MOFs supports investigated in recent years12-16 Heteropoly acids (HPAs) can act as excellent acid, redox, and bi-functional catalysts in a variety of synthetically useful selective transformations of organic substances, due to their strong Bronsted acidity and fast reversible multi-electron redox transformation activities.17 The excellent catalytic performance of HPAs qualifies them as prime candidates for the designed construction of multi-functional materials combining porosity and catalytic activity.18 However, applications of HPAs are limited by their low specific surface area and low stability under catalytic conditions. One of the strategies to overcome these drawbacks consists of their encapsulation within porous solid matrixes19 such as MOFs20. As a well-known MOF, a stable host HKUST-1, Rafiee and Nobakht: H3PW12O40 Encapsulation by Nanoporous ... 310 Acta Chim. Slov. 2016, 63, 309-316 can encapsulated various Keggin-type HPAs, and attractive catalytic performance can be endowed by these HPA-s/HKUST-1.21-23 The opportunity of incorporating HPAs in porous MOFs arises as an attractive pathway to exploit the catalytic activity of these species and opens the opportunity to create new catalytic systems.24 Among the different protocols for the synthesis of useful building blocks, we selected the synthesis of P-keto enol ethers because of their very high impact as synthons for the preparation of bioactive compounds, terpenoids, 4-alkylated-2-cyclohe-xenones, 2-aryl and 2-alkenyl-3- alkoxycyclohexenones and bicycle [2,2,2] octenones.25-27 Also, they act as die-nophiles in Diels-Alder reactions.28 However, the synthesis of P-keto enol ethers has received little attention despite their wide range of applications29-31 and developing a new, cost-effective and green protocol for this transformation is still a challenging task. The present work reports the use of H3PW12O40 on HKUST-1 (PW/HKUST-1) as an active and recyclable catalyst in the synthesis of P-keto enol ethers. 2. Experimental 2. 1. Materials and Preliminary Characterization Copper(II) nitrate trihydrate (99-104%), 1,3,5-ben-zen-tricarboxylate acid (BTC) (98%), cetyl trimethylam-monium bromide (CTAB) (99+%), and PW (99+%) were obtained from Merck. Absolute ethanol (98%), dimedone (98%), n-butylamine (99%), ethyl acetate (98%), n-hexa-ne acetonitrile (98%), propanol (99%), butanol (98%), methanol (98%), tert-butanol (98%), cyclohexanol (99%), benzyl alcohol (99%), 4-methoxybenzyl alcohol (98%), 3-methoxybenzyl alcohol (98%), 2-nitrobenzyl alcohol (97%) and 2-propanol (99.5%) were obtained from Al-drich and used without further purification. (FT-IR) was recorded as KBr pellets using a Shimadzu 470 spectrop-hotometer, spectra range (400-4000 cm-1), wave number accuracy 0.1 cm-1, resolution: 4 cm-1 and about 200 scans were averaged to one spectrum. Morphology of the catalyst was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) on a model XL30 Philips. The size distribution of the samples was obtained using a laser particle size analyzer (HPPS 5001, Malvern, UK) and X-ray diffraction (XRD) pattern of the synthesized catalyst was obtained by using an X-ray diffractometer (Xpert MPD), Co-Ka (k = 0.154 nm) in the angular range 28 = 1-15, step size (28): 0.0200, scan step time (s): 1.0000, scan rate (28) of 5° min-1. The accelerating voltage and applied current were 40 kV and 40 mA, respectively. Brunauer Emmett-Teller (BET) surface areas and pore volumes were measured on a sorptometer kelvin 1042 using nitrogen adsorption at 77 K. The inductively coupled plasma atomic emission spec- troscopy (ICP-AES) on a Spectro Ciros CCD spectrometer were used to leaching measurements. 2. 2. Preparation of the Catalyst PW/HKUST-1 material was prepared from a synthesis mixture containing a molar composition of 5 Cu(NO3)2 ■ 3H2O /2.8 BTC/ 0.3 PW/ 0.6 CTAB. For the synthesis of PW/HKUST-1, the mixture of BTC (0.21 g) and 0.07 g of CTAB in absolute ethanol (12 mL) was prepared, then PW (0.3 g) and Cu(NO3)2 ■ 3H2O (0.4 g) were dissolved in distilled water (10 mL). Both solutions were combined and mixed under vigorous stirring (1000 rpm) for approximately 30 min at room temperature. The mixture was aged without stirring for 4 days at room temperature. The blue solid was then collected by filtration, washed with distilled water three times and dried at 60 °C for 24 h. CTAB was removed by Soxhlet extraction with ethanol performed for 24 h. The product was dried in air at 60 °C for 24 h. 2. 3. Acidity Measurement For the potentiometric titration, 0.05 g of solid was suspended in acetonitrile (90 mL) and stirred for 3 h. The suspension was titrated with a 0.05 mol/L solution of n-butylamine in acetonitrile. The potential variation was measured with a Hanna 302 pH meter using a double junction electrode.32 2. 4. Catalytic Reaction A mixture of dimedone (1.0 mmol) and alcohol (4 mL) was stirred in the presence of the catalyst (0.06 g) at 45 °C. After completion of the reaction as indicated by TLC, the catalyst was separated by decantation (or filtration). The excess alcohol in the filtrate was removed by rotary evaporator and the crude purified by column chro-matography over silica-gel (ethyl acetate/hexane, 1:4). All products were identified by comparing of their spectral data, 1H-NMR 13C-NMR, with those of the authentic samples.31,33-36 3. Results and Discussion 3. 1. Catalyst Characterization The presence of the PW in the HKUST-1 framework was established by FT-IR (Fig. 1). FT-IR spectroscopies confirmed that the structures of HKUST-1 and the PW are retained in the composite PW/HKUST-1. The vibrational spectra of the composite exhibit the characteristic bands of both the HKUST-1 support and the Keggin structure of the phosphotungstate anion. In particular, the FT-IR spectrum of PW contains bands at 1080 cm-1 (PO4), 982 cm-1 (W=O), and 892 and 796 cm-1 (W-O-W). For Rafiee and Nobakht: H3PW12O40 Encapsulation by Nanoporous ... Acta Chim. Slov. 2016, 63, 309-316 311 PW/HKUST-1 the PO4 and W=O vibration bands are shifted in comparison to bulk PW. This shift discloses the confinement effect of PW inside the porous solid. As depicted in Fig. 2 (a, b), the SEM images of the PW/HKUST-1 samples show that the PW/HKUST-1 crystals have octahedral shape with the average size of approximately 300 nm. Fig. 2 (c, d) shows the N2-adsorp- a) Figure 1. FT-IR spectra of (a) PW, (b) PW/HKUST-1, (c) reused PW/HKUST-1, (d) PW/HKUST-1 after reaction with 0.1 mol of pyridine per gram of catalyst and (e) HKUST-1. tion-desorption isotherm and their respective BJH distribution of pore size graph. BJH pore size distribution of PW/HKUST-1 catalyst is presented in Fig. 2 (c) with average pore 3.8 nm. Fig. 2 (d) shows the sorption isotherms, can be classified as type IV (in the IUPAC classification), which is typical of mesoporous materials. The low angle XRD patterns of the PW/HKUST-1 was also evaluated (Fig. 3). According to XRD pattern, synthesis method applied in this study yielded crystalline b) c) d) y * 1 X V r5» * I ■ fjTwf PT ft 100 mV (very strong), 0 < Et < 100 mV (strong), -100 < Et < 0 mV (weak) and Et < -100 mV (very weak) and more acidic in comparison with HKUST-1. PW is well dispersed on the support surface and does not leach during the reaction. Therefore, a larger fraction of active sites are exposed to the surface, and this catalyst may exhibit excellent activity in organic reactions, even with a low catalyst loading. PW/HKUST-1 has an elemental composition comprising 39% W, 16% Cu, 17% C, and 0.56% P which was determined by ICP. 700 600 500 _ 400 > 300 200 100 itj -200 -200 -•-PW — —. PW/HKUST-1 N. —e—HKUST-1 -Ä--- --- 1 1 1 0,5 1 1,5 mmol amine/g catalyst Figure 6. Potentiometrie titration curves of HKUST-1, PW/HKUST-1. PW, 3. 2. Catalytic Reaction The model reaction was carried out for studying the effect of catalyst loading and temperature on the product yield (Scheme 1). Initially, the quantity of the catalyst used in this reaction was optimized (Fig. 7). Influence of the amount of the catalyst on the model reaction was carried out at 45 °C when 4 ml methanol and 1 mmol dime-done were used and mixing rate was 500 rpm. Improve- ment in time of the reaction and yield was observed as the catalyst quantity increased from 0.02 to 0.06 g. Thus, 0.06 g of PW/HKUST-1 was the suitable choice for catalyst loading. Yield of the product was 64, 93, and 95% when reaction temperature was 25, 45, and 60 °C respectively in the presence of 0.06 g of the catalyst and after 5 min. When the reaction temperature reached to 45 °C in the presence of 0.06 g of the catalyst the best result was obtained. According to the potentiometric titration results it seems that this yield was achieved per 0.084 mmol of active site of the catalyst (n = 1.4 total number of acidic sites; mmole acid site/g of the catalyst). When PW neat was used as catalyst in this optimized reaction conditions 94% of the corresponding product was obtained after 5 min, but the catalyst is in homogenous phase and hard recovery of the catalyst is as a disadvantages of this method. For comparison, the HKUST-1 material in the absence of PW, was used as a catalyst in the model reaction. The porous HKUST-1 itself shows 31% yield after 20 Figure 7. Effect of catalyst loading in the model reaction (4 ml methanol, 1 mmol dimedone, and mixing rate: 500 rpm at 45 °C). 1 itttdI 4 II i I ul Scheme 1. Model reaction for the synthesis of P-keto enol ethers using PW/HKUST-1 Rafiee and Nobakht: H3PW12O40 Encapsulation by Nanoporous ... 314 Acta Chim. Slov. 2016, 63, 309-316 min. This observation revealed that Keggin PW species occluded in HKUST-1 pores significantly improved the catalytic activity of HKUST-1. To evaluate the scope of the PW/HKUST-1 for the synthesis of P-keto enol ethers, different alcohols were used as reactants (Table 1). Primary, and secondary alcohols, reacted with dimedone without any significant difference to give the corresponding products in good to excellent yields. tert-Butanol was also reacted with dimedone to provide the corresponding P-keto enol ether in 50% yield (entry 6), while some previous approaches did not apply this alcohol or gave negative results for similar reac-tions.34-36,39,40 Table 1 Synthesis of ß-keto enol ethers using PW/HKUST-1 as catalyst. Entry Alcohols Time (min) Yield )%( 1 MeOH 5 98 2 EtOH 10 98 3 Propanol 10 91 4 Butanol 75 86 5 ^^-OH 30 92 6 -1-(111 75 51 7 cr 25 98 8 (T- 75 94 9 i'Tv 20 93 10 11 12 15 30 55 92 64 71 a Isolated yields, all products were identified by comparing their spectral data with those of the authentic samples.21-24,28,29 3. 3. Catalyst Recyclability The recyclability of the PW/HKUST-1 was investigated to test the efficiency of this catalyst in consecutive cycles for the synthesis of P-keto enol ethers. The solid catalyst was recovered at the end of each reaction by simple filtration followed by washing with MeCN, dried at 60 °C and then reused in a fresh model reaction using the same experimental conditions. The results in Fig. 8 showed that synthesis of the product could reach 94% after being recycled for four times. It was observed that the catalytic system could be recycled at least four times with little decrease in catalytic activity and the amount of weight losing in this form of recovery was 5.5 wt.% but in continuous reaction system of course it should be considered more. TFT- ■ Y I#I 100 mV. This nano catalyst was successfully used for the synthesis of various P-keto enol ethers at 45 °C with 51-98% yield after 5-75 min. The catalyst was easily recycled and reused at least four times without significant loss of its activity (94% yield after forth run). The presence of the PW in PW/HKUST-1 and reused PW/HKUST-1 structure, eliminating any doubt about collapse of the HKUST-1 after catalytic reaction was followed by FT-IR, XRD and SEM techniques. Bronsted and Lewis acidity of the PW/HKUST-1 catalyst was distinguished by studying the FT-IR. The strength and dispersion of the protons on PW/HKUST-1 was considerably high and active surface protons became more available for reactant. 5. Acknowledgements The authors thank the Razi University Research Council and Iran National Science Foundation (INSF) for support of this work. 6. References 1. Y. Liu, J. Liu, Y. S. Lin, Micropor. Mesopor. Mater. 2015, 214, 242-245. http://dx.doi.org/10.1016/j.micromeso.2015.05.001 2. J. Lee, O. K. Farha, J. Robe, K. A. Scheidt, S. T. Nguyen, J. T. Hupp, Chem. Soc. Rev. 2009, 38, 1477-1504. http://dx.doi.org/10.1039/b802426j 3. M. Zhao, S. Ou, C. D. Wu, Acc. Chem. Res. 2014, 47, 1199-1207. http://dx.doi.org/10.1021/ar400265x 4. M. Ranocchiari, J. A. van Bokhoven, Chem. Phys. 2011, 13, 6388-6396. 5. J. R. Li, R. J. Kuppler, H. C. Zhou, Chem. Soc. Rev. 2009, 38, 1477-1504. http://dx.doi.org/10.1039/b802426j 6. F. Ke, Y. P. Yuan, L. G. Qiu, Y. H. Shen, A. J. Xie, J. F. Zhu, X. Y. Tian, L. D. Zhang, J Mater Chem. 2011, 21, 38433848. http://dx.doi.org/10.1039/c0jm01770a 7. D. Zhao, S. Tan, D. Yuan, W. Lu, Y.H. Rezenom, H. Jiang, L. Q. Wang, H.C. Zhou, Adv. Mater. 2011, 23, 90-93. http://dx.doi.org/10.1002/adma.201003012 8. L. N. Duan, Q. Q. Dang, C. Y. Han, X. M. Zhang, Dalton Trans. 2015, 44, 1800-1804. http://dx.doi.org/10.1039/C4DT02672A 9. C. M. Granadeiroa, A. D. S. Barbosa, P. Silva, F. A. A. Paz, V. K. Saini, J. Pires, B. de Castro, S. S. Balula, L. Cunha-Sil-va, Appl. Catal. A: General. 2013, 453, 316-326. http://dx.doi.org/10.1016Zj.apcata.2012.12.039 10. A. Corma, H. Garcia, F. X. L. Xamena, Chem. Rev. 2010, 110, 4606-4655. http://dx.doi.org/10.1021/cr9003924 11. A. Micek-Ilnickaa, B. Gil, Dalton. Trans. 2012, 41, 1262412629. http://dx.doi.org/10.1039/c2dt31329d 12. M. Grilc, B. Likozar, J. Levec, ChemCatChem. 2016, 8, 180-191. http://dx.doi.org/10.1002/cctc.201500840 13. M. Grilc, B. Likozar, J. Levec, Catalysis today. 2015, 256, 302-314. http://dx.doi.org/10.1016/j.cattod.2015.02.034 14. T. Birsa Celic, M. Grilc, B. Likozar, N. Novak Tušar, Chem-SusChem. 2015, 8, 1703-1710. http://dx.doi.org/10.1002/cssc.201403300 15. Y. Zhou, J. Song, S. Liang, S. Hu, H. Liu, T. Jiang, B. Han, J. Mol. Catal. A: Chem. 2009, 308, 68-72. http://dx.doi.org/10.1016Zj.molcata.2009.03.027 16. H. R. Moon, D. W. Lim, M. P. Suh, Chem. Soc. Rev. 2013, 42, 1807-1824. http://dx.doi.org/10.1039/C2CS35320B 17. C. L. Hill, C. M. Prosser-McCartha, Coord. Chem. Rev. 1995, 143, 407-455. http://dx.doi.org/10.1016/0010-8545(95)01141-B 18. C. Zou, Z. J. Zhang, X. Xu, Q. H. Gong, J. Li, C. D. Wu, J. Am. Chem. Soc. 2012, 134, 87-90. http://dx.doi.org/10.1021/ja209196t 19. R. Yu, X. F. Kuanga, X. Y. Wu, C. Z. Lu, J. P. Donahue, Coord. Chem. Rev. 2009, 253, 2872-2890. http://dx.doi.org/10.1016/j.ccr.2009.07.003 20. L. Yang, H. Naruke, T. Yamase, Inorg. Chem. Commun. 2003, 6, 1020-1024. http://dx.doi.org/10.1016/S1387-7003(03)00172-2 21. D. Y. Du, J. S. Qin, S. L. Li, Z. M. Su, Y. Q. Lan, Chem. Soc. Rev. 2014, 43, 4615-4632. http://dx.doi.org/10.1039/c3cs60404g 22. N. Janssens, L. H. Wee, S. Bajpe, E. Breynaert, C. E. A. Kirschhock, J. A. Martens, Chem. Sci. 2012, 3, 1847-1850. http://dx.doi.org/10.1039/c2sc01102f 23. H. Yang, J. Li, L. Wang, W. Dai, Y. Lv, S. Gao, Catal. Commun. 2013, 35, 101-104. http://dx.doi.org/10.1016/j.catcom.2013.02.013 24. C. L. Hill, J. Mol. Catal. A: Chem. 2007, 262, 2-6. http://dx.doi.org/10.1016/j.molcata.2006.08.042 25. H. Olivier-Bourbigou, L. Magna, D. Morvan, Appl. Catal. A: Gen. 2010, 373, 1-56. http://dx.doi.org/10.1016/j.apcata.2009.10.008 26. M. Curini, F. Epifano, S. Genovese, Tet. lett. 2006, 47, 46974700. 27. A. S. Kende, J. Lan, D. Arad, Tet. Lett. 2002, 43, 5237 -5239. http://dx.doi.org/10.1016/S0040-4039(02)01065-1 28. M. F. Scott, T. P. Robinson, D. J. Goldsmith, J. P. Bowen, Tet. Lett. 1999, 40, 459-462. http://dx.doi.org/10.1016/S0040-4039(99)01611-1 29. B. Banerjee, S. K. Mandal, S. C. Roy, Chem. Lett. 2006, 35, 16-17. http://dx.doi.org/10.1246/cl.2006.16 30. Z. S. Cui, Z. H. Zhang, S. F. Liu, J. Chem. Res. 2006, 3, 390-393. http://dx.doi.org/10.3184/030823406777946815 31. B. Das, K. Laxminarayana, B. Ravikanth, J. Mol. Catal. A: Chem. 2007, 271, 131-133. http://dx.doi.org/10.1016/j.molcata.2007.02.041 32. E. Rafiee, M. Joshaghani, S. Eavani, S. Rashidzadeh, Green Chem. 2008, 10, 982-989. http://dx.doi.org/10.1039/b803249a Rafiee and Nobakht: H3PW12O40 Encapsulation by Nanoporous ... 316 Acta Chim. Slov. 2016, 63, 309-316 33. K. Funabiki, T. Komeda, Y. Kubota, M. Matsui, Tetrahedron 2009, 65, 7457-7463. http://dx.doi.Org/10.1016/j.tet.2009.07.012 34. P. Thirupathi, S. S. Kim, Tetrahedron 2010, 66, 2995-3003. http://dx.doi.Org/10.1016/j.tet.2010.02.063 35. E. Rafiee, M. Khodayari, M. Joshaghani, Can. J. Chem. 2011, 89, 1533-1538. http://dx.doi.org/10.1139/v11-134 36. E. Rafiee, M. Khodayari, M. Kahrizi, R. Tayebe, J. Mol. Ca-tal. A: Chem. 2012, 358, 121-128. http://dx.doi.org/10.1016/j.molcata.2012.03.005 37. G. Ferey, C. Mellot-Draznieks, C. Serre, F. Millange, J. Du- tour, S. Surble, I. Margiolaki, Science 2005, 309, 20402042. http://dx.doi.org/10.1126/science.1116275 38. D. P. Sawant, A. Vinu, N. E. Jacob, F. Lefebvre, S. B. Halli-gudi, J. Catal. 2005, 235, 341-352. http://dx.doi.org/10.1016/jjcat.2005.08.010 39. R. Murugan, R. Kamakshi, B. S. R. Reddy, Aust. J. Chem. 2005, 58, 228-230. http://dx.doi.org/10.1071/CH04249 40. P. Srihari, S. S. Mandal, J. S. S. Reddy, R. S. Rao, J. S. Ya-dav, Chin. Chem. Lett. 2008, 19, 767-770. http://dx.doi.org/10.1016Zj.cclet.2008.05.006 Povzetek Hibridni kompozitni material smo pripravili z enkapsulacijo H3PW12O40 (PW) v HKUST-1 (Cu3(BTC)2, BTC=1,3,5-benzenetrikarboksilan kislina), v molarnem razmerju 5 Cu(NO3)2-3H2O /2.8 BTC/ 0.3 PW/ 0.6 CTAB z dodatkom raztopine H3PW12O40 in soli bakra v mešanico BTC-ja in surfaktanta. Katalizator smo karakterizirali z naslednjimi tehnikami: rentgensko praškovno difrakcijo (XRD), infrardečo spektroskopijo (FT-IR), vrstično elektronsko spektroskopijo (SEM), energijsko disperzivno rentgensko spektroskopijo (EDX), laserskim analizatorjem za določanje velikosti delcev in Brunauer Emmett-Teller metodo (BET). Kislost katalizatorja smo izmerili s potenciometrično titracijo z n-butilami-nom in v materialu PW/HKUST-1 določili zelo kisla mesta z Ei > 100 mV. Tako pripravljen nanokatalizator smo uspešno uporabili za sintezo različnih P-keto enol etrov pri 45 °C z izkoristki od 51 % do 98 % in časom reakcij med 5 in 75 minut. Katalizator smo lahko reciklirali in ponovno uporabili brez znantnega zmanjšanja njegove aktivnosti (94 % izkoristek po četrtem ciklu). Prisotnost PW v strukturi PW/HKUST-1 in v strukturi ponovno uporabljenega PW/HKUST-1 odpravlja vse dvome o kolapsu HKUST-1 po katalitični reakciji in jo lahko zasledujemo s FT-IR, XRD in SEM tehnikami. Bronstedovo in Lewisovo kislost PW/HKUST-1 katalizatorja smo določili z FT-IR metodo in kemo-sorbcijo piridina. Moč in disperzija protonov na PW/HKUST-1 je bila precej visoka, aktivna površina protonov pa je postala dostopnejša za reaktante. Rafiee and Nobakht: H3PW12O40 Encapsulation by Nanoporous ... DOI: 10.17344/acsi.2016.2245 Acta Chim. Slov. 2016, 63, 317-322 317 Scientific paper Effect of Process Parameters on the Size and Shape of Nano- and Micrometric Zinc Oxide Jolanta Pulit-Prociak,1* and Marcin Banach1 1 Cracow University of Technology, Faculty of Chemical Engineering and Technology, 24 Warszawska St., 31-155 Cracow, Poland * Corresponding author: E-mail: jolantapulit@indy.chemia.pk.edu.pl Tel. +48 12 628 20 92, fax. +48 12 628 20 35 Received: 13-01-2016 Abstract The paper presents a method of obtaining zinc oxide nano- and microparticles. In these studies microwave reactor and laboratory pressure reactor were used. Since microwave radiation accelerates proceeding of reactions, this way was found to be an effective method in the process of obtaining nanocrystallines of zinc oxide. The size of prepared particles rarely exceeded 500 nm. Keywords: Zinc oxide, nanoparticles, green chemistry 1. Introduction Metal oxides occurring in nanometric scale are characterized by more valuable properties comparing to the characteristics of the same macro-scale-materials.1 Such structures may be defined by ratio of surface area to their mass. This value is large enough so that other material properties are determined by surface properties. Due to their larger ratio of surface area to volume, they exhibit a higher chemical activity.2 Increased chemical activity of such materials may be explained by analyzing their structure. The size of the nanoparticles surface area increases significantly with decreasing their size. Small nanoparticle with a diameter of 1 nm has 100% of atoms disposed on its surface, while the particle with diameter of 10 nm has only 15% of surface atoms. Therefore, smaller particles are more chemically reactive.3 Zinc oxide is known primarily for its bleaching properties. It is used as inorganic pigment,4'5 catalyst6'7 as well as sunglasses or wood coating material.8 Thanks to the fact that it is transparent for visible wavelength range of sunlight nanosized zinc oxide may be used as a blocker of harmful ultraviolet irradiation.910 In addition, zinc oxide nanoparticles have antibacterial and wound-healing properties.1112 Thanks to their biocidal properties they found application for example in the production of antimicrobial textiles.13 Since zinc oxide has valuable electrical, optielectronic and photochemical properties, it has been also used in electrotechnique.14 There are many methods for the preparation of zinc oxide in the nanocrystalline form. Nawaz and colleagues have described a synthesizing of zinc nanooxide by wet chemical method using zinc nitrate, sodium hydroxide and starch which served as stabilizing agent. Obtained product exhibited antibacterial properties.15 Parashar synthesized nanometric zinc oxide by mixing an organic solution of a zinc precursor with an alcoholic base solution and adding acetone in order to precipitate a milky white zinc oxide.16 Nanometric zinc oxide may be also synthesized by metallurgical and mechanochemical processes, controlled precipitation method as well as by solgel, solvothermal and hydrothermal methods.17 Ohara and colleagues obtained highly crystalline zinc oxide nanopar-ticles by the way of supercritical water hydrothermal synthesis.18 In this paper studies on obtaining zinc oxide nano-and microparticles in a field of microwave radiation and in the laboratory pressure reactor have been described. The aim of the work was to also compare the physicochemical properties of obtained products. 2. Experimental 2. 1. Materials Zinc nitrate hexahydrate (>99.0%) was used as zinc precursor. Sodium hydroxide (>98%) served as pre- Prociak and Banach: Effect of Process Parameters on the Size and Shape 318 Acta Chim. Slov. 2016, 63, 317-322 cipitating substance. Both chemicals were obtained from Sigma Aldrich. Solutions were prepared in deionized water. 2. 2. Methods The first phase of studies was common for both types of processes. It concerned the precipitation of zinc hydroxide by adding an aqueous solution of sodium hydroxide to an aqueous solution of zinc nitrate. The process runs at room temperature under continuous stirring. Sodium hydroxide was used in a stoichiometric amount. Accurate amounts of raw materials used are presented in Table 1. Table 1. Substrates used in the precipitation process Reagent Molar concentration, c [mol/dm3] Volume, V [cm3] Zn(NO)3 NaOH 0.1 2.0 25 2.5 In a further step, a dehydration process occurred. In order to accelerate that process, zinc hydroxide suspension was subjected to elevated temperature and pressure treatment. It was expected that the acceleration of dehydration process by applying elevated heat and pressure, promotes the formation of smaller crystallites of zinc oxide so that their size would be in the nanometric range. For this purpose, the suspension was transferred to a microwave reactor or laboratory pressure reactor. 2. 2. 1. Processes Carried Out in a Microwave Reactor The use of polar solvent (water) in the field of microwave radiation is possible to efficiently transfer the heat in a short time in the whole volume of the reaction mixture, which accelerates the process of dehydration. Dehydration processes carried out in a microwave reactor were varied directly through selection of different temperature-pressure conditions. In fact, these parameters were determined by specific values of microwave power and the residence time of the sample in the microwave field. Microwave power and residence time were independent parameters. They took three levels of volatility. The temperature and pressure values were read from plots generated in the program which assists the software dedicated to microwave reactor Magnum II from Ertec Poland. Process parameters are given in Table 2. 2. 2. 2. Processes Carried Out in a Laboratory Pressure Reactor Parameters of processes carried out in the laboratory pressure reactor (PARR 4525) were chosen arbitrarily, on the basis of preliminary studies. Their exact values are presented in Table 3. Obtained suspensions were filtered on Buchner funnel using Whatman filters (d = 0.45 pm) and washed with 160 cm3 of deionized water so as sodium nitrate would be removed. Solids were dried in air-dryer at 50 °C within 2 hours. Obtained products were analyzed by instrumental techniques. In the course of scanning electron microscopy a determination of the shape and indirect determination of Table 2. Parameters of dehydration processes carried out in microwave reactor Input variables Temperature Pressure dmed [nm] dmed [nm] Sample Microwave Residence achieved achieved (based on (based on power [%] time [min] [°C] [bar] SEM) Scherrer eq. M1 70 3 100 9 20-200 31 M2 70 5 160 15 10-200 31 M3 70 7 200 26 20-200 30 M4 85 3 100 11 50-300 27 M5 85 5 180 25 100-200 2S M6 85 7 230 39 40-250 22 M7 100 3 110 14 40-200 2S MS 100 5 200 39 S0-200 30 M9 100 7 240 39 60-250 30 Table 3. Parameters of dehydration processes carried out in laboratory pressure reactor Sample Input variables Temperature [°C] Process time [min] Pressure achieved [bar] dmed [nm] (based on SEM) dmed [nm] (based on Scherrer eq.) R1 120 30 1 200-400 32 R2 160 30 4 50-400 30 R3 200 30 14 30-200 30 Prociak and Banach: Effect of Process Parameters on the Size and Shape Acta Chim. Slov. 2016, 63, 317-322 319 Fig. 1. Photomicrographs of obtained products Prociak and Banach: Effect of Process Parameters on the Size and Shape ... 320 Acta Chim. Slov. 2016, 63, 317-322 zinc oxide particles size was possible. The study was carried out using 1430 VP microscope from LEO Electron Microscopy Ltd. In order to reveal the crystal structure, the sample was subjected to X-ray analysis conducted on X-ray diffractometer X'Pert PW 1752/00 from Philips. In order to detect vibrations characteristic of zinc oxide, samples were subjected to Fourier transform infrared spectroscopy. For this purpose spectrophotometer Nicolet 380 from Nicolet was used. 3. Results and Discussion Preparation of zinc oxide proceeds according to the following equations: Zw(AfiGj), +2NaOH->Zn(OH),+2NaNO, 3. 1. Scanning Electron Microscopy Figure 1 presents SEM photomicrographs of obtained products. The shape of obtained agglomerates may be defined as diverse and inhomogenous. It may be concluded that shape and size of particles depend on the conditions of their preparation. Comparing both reactors, it has been found out that the greater degree of variation in particles shape was reached when microwave reactor was used. Despite a greater diversity of shape and size of products obtained in the microwave radiation field, the particles size was ranged from 10 to 300 nm, while the particles obtained in the laboratory pressure reactor were larger -their medium diameter was in the range from 30 to 400 nm. Moreover, the influence of temperature on the minimum size difference between the largest and smallest particles is perceptible. Higher temperature determines lower size variation. It favours obtaining larger number of particles which are characterised by less diversified size. On the other hand, the mean particle size is dependent mostly on the dehydration time. When using microwave reactor, one may observe that initially the mean particles size decreases when residence time is elongated. After exceeding some time (5 minutes), the particles size slightly increases. This may be due to the fact that small particles form larger agglomerates which take place in final phase of the process. Products obtained in the course of hydrothermal synthesis within 5 min are characterized by physicoche-mical properties which are similar to properties of products obtained in a laboratory pressure reactor within 30 min. 3. 2. X-ray Analysis Results of X-ray analysis are presented in Figure 2. The resulting diffractogram indicates the receipt of zinc oxide. Peaks occurring in the area of 32°, 34° and 36° of 28 diffraction angle correspond to strong Bragg reflection. The incidence of these peaks is characteristic for zinc Effect of Process Parameters on the Size and Shape Acta Chim. Slov. 2016, 63, 317-322 321 oxide.19 Other reflections were not detected, which indicates high purity of samples. Peak intensity provides high crystallinity of products and their width reflects small size of crystallites. The size of crystallites was also calculated based on Scherrer equation: addition, processes occur more efficiently when using microwave radiation. Thanks to the using of microwave irradiation, it is possible to efficiently transfer the heat in a short time throughout the whole volume of the reaction mixture, which greatly speeds up the processes completion. (2) where K - dimensionless shape factor (K = 0.9) X - X-ray wavelength [nm] P - full width of peak at half maximum 0 - Bragg angle Values of calculated crystallites size are given in Tables 2 and 3. It should be noted that these size values concern the size of individual crystallites, which may consist the structure of nano- and microparticles that are characterized by larger sizes. 3. 3. Fourier Transform Infrared Spectroscopy Figure 3 presents typical FT-IR spectra of zinc oxide. During the FT-IR analysis a distinct characteristic absorption band at 440 cm-1 has been revealed. This band may be assigned to stretching vibrations of Zn-O. Other bands are derived from water present in products (stretching vibrations of O-H at 3400 cm-1) and Zn-OH at 880 cm-1.20,21 N 1 ■'' ' \\ _J,—\ A --yf* N^Vt --- \ /S -""** \\ vy — M2 — MB I ---R3 fV -, 4000 3600 3200 2800 2400 2000 Wavenumberi cm"1 1600 1200 600 Fig. 3. FT-IR spectrum of obtained samples 4. Conclusions It was possible to obtain zinc oxide particles both under microwave irradiation and in the laboratory pressure reactor. However, particles are distinguished by their varied shape and size. In general, they have lower average size in the case of obtaining them under microwave radiation. In 5. Acknowledgements This work is a part of the project Synthesis and Application of Innovative Nanomaterials with Antimicrobial Properties supported by National Centre for Research and Development under the Project LIDER/03/146/L-3/11/NCBR/2012 for the period of 2012-2015. 6. References 1. P. H. C. Camargo, K. G. Satyanarayana, F. Wypych, Mater. Res. 2009, 12, 1-39. http://dx.doi.org/10.1590/S1516-14392009000100002 2. E. Roduner, Chem. Soc. Rev. 2006, 35, 583-592. http://dx.doi.org/10.1039/b502142c 3. C. Rao, G. Lulkarni, P. Thomas, P. Edwards, Chem. Eur. J. 2002, 8, 29-35. http://dx.doi.org/10.1002/1521-3765(20020104)8:1<28: :AID-CHEM28>3.0.C0;2-B 4. M. M. Mikhailov, V. V. Neshchimenko, S. He, C. Li, J. Spacecraft. Rockets. 2011, 48, 891-896. http://dx.doi.org/10.2514/L42974 5. C. Li, V. V. Neshchimenko, M. M. Mikhailov, International Journal of Chemical, Nuclear, Metallurgical and Materials Engineering, 2014, 8, 388-392. 6. M. S. Spencer, Top. Catal. 1999, 8, 259-266. http://dx.doi.org/10.1023/A:1019181715731 7. W. A. Lazier, H. Adkins, J. Am. Chem. Soc. 1925, 47, 7191722. http://dx.doi.org/10.1021/ja01683a033 8. F. Weichelt, M. Beyer, R. Emmler, R. Flyunt, E. Beyer, M. Buchmeiser, Macromol. Symp. 2011, 301, 23-30. http://dx.doi.org/10.1002/masy.201150304 9. A. A. Keller, W. Vosti, H Wang, A. Lazareva, J. Nanopart. Res. 2014, 16, Article ID 2489. 10. T. G. Smijs, S. Pavel, Nanotechnol. Sci. Appl. 2011, 4, 95-112. http://dx.doi.org/10.2147/NSA.S19419 11. A. A. Tayel, W. F. El-Tras, S. Moussa, A. F. El-Baz, H. Ma-hrous, M. F. Salem, L. Brimer, J. Food Safety. 2011, 31, 211-218. http://dx.doi.org/10.1111/j.1745-4565.2010.00287.x 12. J. W. Wang, A. Cao, Y. Jiang, X. Zhang, J. H. Liu, Y. Liu, W. Hang, ACS Appl. Mater. Interfaces. 2014, 6, 2791-2798. http://dx.doi.org/10.1021/am4053317 13. R. Rajendran, C. Balakumar, H. A. M. Ahammed, S. Jayaku-mar, K. Vaideki, E. M. Rajesh, Int. J. Eng. Sci. Technol. 2010, 2, 202-208. 14. S. Kumar, P. Venkateswarlu, V. R. Rao, G. N. Rao, Int. Nano. Lett. 2013, 3, 30-35. Prociak and Banach: Effect of Process Parameters on the Size and Shape ... 322 Acta Chim. Slov. 2016, 63, 317-322 http://dx.doi.org/10.1186/2228-5326-3-30 15. H. R. Nawaz, B. A. Solangi, B. Zehra, U. Nadeem, Can. J. Sci. Ind. Res. 2011, 2, 164-170. 16. S. Parashar, Process for the preparation of nano zinc oxide particles, US Patent Number 20,110,002,970 A1, date of patent January 6, 2011. 17. A. Kolodziejczak-Radzimska, T. Jesionowski, Materials. 2014, 7, 2833-2881. http://dx.doi.org/10.3390/ma7042833 18. S. Ohara, T. Mousavand, M. Umetsu, S. Takami, T. Adschiri, Solid State Ionics. 2004, 172, 261-264. http://dx.doi.org/10.1016Zj.ssi.2004.02.044 19. H. Kumar, R. Rani, Int. Lett. Chem. Phys. Astron. 2013, 14, 26-36. http://dx.doi.org/10.18052/www.scipress.com/ILCPA.19.26 20. K. Nejati, Z. Rezvani, R. Pakizevand, Int. Nano Lett. 2011, 1, 75-81. 21. K. Sowri Babu, Ramachandra Reddy, C. Sujatha, K. Venugo-pal Reddy, A. N. Mallika, J. Adv. Ceram. 2013, 2, 260-265. http://dx.doi.org/10.1007/s40145-013-0069-6 Povzetek V prispevku je predstavljena metoda priprave nano in mikrodelcev cinkovega oksida. ZnO smo pripravili pri povišani temperaturi in tlaku bodisi z uporabo mikrovalov ali uporabo ustreznih laboratorijskih reaktorjev. Mikrovalovi pospešijo potek reakcij, zato je metoda mirovalovne sinteze učinkovita v procesu priprave nanodelcev ZnO. Velikost delcev ZnO je redko presegla 500 nm. Prociak and Banach: Effect of Process Parameters on the Size and Shape DOI: 10.17344/acsi.2016.2246 Acta Chim. Slov. 2016, 63, 323-326 323 Scientific paper New Iridium Complex Coordinated with Tetrathiafulvalene Substituted Triazole-pyridine Ligand: Synthesis, Photophysical and Electrochemical Properties Zhi-Gang Niu, Hui Xie, Li-Rong He, Kai-Xiu Li, Qing Xia, Dong-Min Wu, Gao-Nan Li* College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, PR China * Corresponding author: E-mail: ligaonan2008@163.com, niuzhigang1982 @ 126.com Received: 13-01-2016 Abstract A new iridium(III) complex based on the triazole-pyridine ligand with tetrathiafulvalene unit, [Ir(ppy)2(L)]PF6 (1), has been synthesized and structurally characterized. The absorption spectra, luminescent spectra and electrochemical behaviors of L and 1 have been investigated. Complex 1 is found to be emissive at room temperature with maxima at 481 and 510 nm. The broad and structured emission bands are suggested a mixing of 3LC (3n-n*) and 3CT (3MLCT) excited states. The influence of iridium ion coordination on the redox properties of the TTF has also been investigated by cyclic voltammetry. Keywords: Iridium(III) complexes; Tetrathiafulvalene; Triazole-pyridine ligands; Photoluminescence; Cyclic voltam-metry 1. Introduction For several decades, tetrathiafulvalene (TTF) and its derivatives were extensively developed by scientists in photofunctional materials1-8 because of their strongly electron-donating and attractive reversible redox properties. As a consequence, a large synthetic effort has also been devoted to the preparation of materials that exhibit synergy or coexistence between conductivity and luminescence. Coordination of TTF-containing ligands to transition metal centers is typically achieved by functio-nalizing TTF with nitrogen atom.9 Very recently, we have reported a new nitrogen-containing TTF-based ligand, 2-(1-(2-((4',5'-bis(methylthio)-[2,2'-bi(1,3-dithiolylidene)]-4-yl)thio)ethyl)-1H-1,2,3-triazol-4-yl)pyridine (L). Ligand L was used as the polyp- prtppirfcClh (l=lf N UIHKjPFi PI'S Scheme 1. Synthetic routes of Ir(III) complex 1. Niu et al.: New Iridium Complex Coordinated with Tetrathiafulvalene . 324 Acta Chim. Slov. 2016, 63, 323-326 yridine NAN ligand and binap/xantphos as diphosphines PAP ligand to form two Cu(I) complexes, [Cu(I)(Binap) (L)]BF4 and [Cu(I)(Xantphos)(L)]BF4, which exhibited advantageous electrochemical and photophysical properties.10 The results hence led us to further design other metal complexes based on the TTF-containing thioethyl-bridged triazole-pyridine ligand. Iridium(III) complexes have widely been employed in organic light-emitting devices (OLEDs), as they have high phosphorescence quantum efficiency, long excited-state lifetime and excellent color tenability.11-14 Therefore, the association of the redox-active TTF unit with cyclo-metalated iridium(III) complex is intriguing in coordination chemistry and material chemistry. In this work, we report the synthesis of a new bis-cyclometallated TTF-ba-sed iridium(III) complex with ppy as CAN ligand, [Ir(ppy)2(L)]PF6 (1) (Scheme 1). Their electrochemical and photophysical properties are also investigated. 2. Experimental 2. 1. Materials and Measurements 2-(1-(2-((4',5'-bis(methylthio)-[2,2'-bi(1,3-dithioly-lidene)]-4-yl)thio)ethyl)-1#-1,2,3-triazol-4-yl)pyridine (L) was synthesized in our previous work,8 and an improved preparation method was used to synthesize the cyclo-metalated iridium chlorobridged dimer [Ir(ppy)2Cl]2 in good yield.15 All solvents were dried using standard procedures. Solvents used for electrochemistry and spectros-copy were spectroscopic grade. 1H NMR and 13C NMR spectra were recorded on a Bruker AM 400 MHz instrument. Chemical shifts were reported in ppm relative to Me4Si as internal standard. FT-IR spectra were taken on a Nicolet 6700 FTIR spectrometer (400-4000 cm-1) with KBr pellets. ESI-MS spectra were recorded on an Esquire HCT-Agilent 1200 LC/MS spectrometer. The elemental analyses were performed on a Vario EL Cube Analyzer system. UV-vis spectra were recorded on a Hitachi U3900/3900H spec-trophotometer. Fluorescence spectra were carried out on a Hitachi F-7000 spectrophotometer. 2. 2. Synthesis of [Ir(ppy)2(L)]PF6 (1) A mixture of a dimer [Ir(ppy)2Cl]2 (50 mg, 46.5 pmol) and L (58 mg, 93.0 pmol) was dissolved in 6 mL of DCM and MeOH (v/v = 1 : 1) and refluxed for 6 h under nitrogen. The orange-red solution was then cooled to room temperature and NH4PF6 (38 mg, 0.23 mmol) was added to the solution. The mixture was stirred at room temperature for 4 h, and then evaporated to dryness. The solid was purified by column chromatography with DCM/MeOH (100 : 1) eluent to afford pure product 1 (54 mg, Yield: 50.5 %) as a yellow solid. 1H NMR (400 MHz, CDCl3): 5 9.04 (s, 1H), 8.27 (d, J = 8.0 Hz, 1H), 7.99 (t, J = 73.6 Hz, 1H), 7.90-7.92 (m, 2H), 7.82 (d, J = 4.2 Hz, 1H), 7.65-7.79 (m, 6H), 7.53 (d, J = 5.6 Hz, 1H), 6.88-7.08 (m, 6H), 6.40 (d, J = 7.2 Hz, 1H), 6.31 (d, J = 6.8 Hz, 1H), 5.97 (s, 1H), 4.63 (t, J = 6.0 Hz, 2H), 3.12-3.15 (m, 2H), 2.42 (s, 6H). 13C NMR (100 MHz, CDCl3): 5 168.2, 167.6, 150.0, 149.9, 149.7, 149.5, 148.7, 148.5, 146.2, 143.8, 143.7, 139.7, 138.1, 138.0, 132.0, 131.9, 130.7, 130.2, 129.1, 127.9, 127.1, 126.6, 126.3, 124.8, 124.5, 123.5, 123.1, 122.8, 122.6, 121.6, 119.5, 119.4, 114.5, 108.9, 49.6, 34.8, 29.7; ESI-MS (m/z): 1001.0 [M-PF6]+. IR (cm-1): v = 3442 (m), 2922 (w), 2853 (w), 1608 (m), 1475 (m), 1422 (m), 1265 (w), 1100 (w), 842 (s), 756 (m), 556 (w). Anal. calcd. For C39H32F6IrN6PS7: C 40.86, H 2.81, N 7.33; found: C 40.95, H 2.96, N 7.45. 2. 3. Cyclic Voltammetry Cyclic voltammetry (CV) was performed on a CHI 1210B electrochemical workstation, with a glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, an aqueous saturated calomel electrode (SCE) as the reference electrode, and 0.1 M n-Bu4NClO4 as the supporting electrolyte. 3. Results and Discussion 3. 1. Photophysical Properties 3. 1. 1. Absorption Properties The absorption spectra of L and 1 in dichlorometha-ne solution at room temperature are depicted in Fig. 1. For ligand L and complex 1, these strong absorption bands at a high energy (À < 350 nm) are assigned to spin-allowed intraligand (tc^tc*) transitions of TTF-TzPy ligand (L) or ancillary ligand (ppy). The moderate absorption bands at lower energy (350-450 nm) correspond to intramolecular charge-transfer transition (ICT) for L16 and metal-to-li-gand charge-transfer (MLCT, dn(Ir)^n*(L)) transition for 1, respectively.17,18 3. 1. 2. Emission Properties The relative emission spectra of ligand L and complex 1 in degassed CH2Cl2 solution at room temperature are also given in Fig. 1. Upon excitation at 438 nm, complex 1 displays two intense emission maxima at ca. 481 and 510 nm. As for L, the emission band occurs at about 462 nm (^ex = 363 nm). Therefore the vibronically structured emission of 1 is probably derived from a mixing of 3LC (3n-n*) and 3CT (3MLCT) excited states.19,20 3. 2. Electrochemical Properties The electrochemical behaviors of the ligand L and iridium complex 1 were investigated by cyclic voltamme- Niu et al.: New Iridium Complex Coordinated with Tetrathiafulvalene . Acta Chim. Slov. 2016, 63, 323-326 325 Wavelength i Fig. 1: UV and FL spectra of ligand L and complex 1 in CH2Cl2 try in CH2Cl2 solution (Fig. 2 and Table 1). Both compounds (L and 1) exhibit two reversible one-electron oxidation processes, which are associated with the successive oxidation of the TTF unit to TTF+ and TTF2+. Additionally, complex 1 show a irreversible oxidation peak (Epox) at 1.88 V, which is attributed to the metal-centered Ir3+/Ir4+ oxidation couple.21,22 In comparison with the ligand L, the two oxidation waves for complex 1 are shifted to more negative potentials. The observed results are different from the previous reported work,23 it is possible that the tria-zole-pyridine unit is grafted on the TTF core through a non-conjugated spacer group, which is disadvantageous to intramolecular electron transfer and communications.10 Table 1: Redox potentials of ligand L and complex 1 Compounds E^OV " E,22(V) " Ep0K (Ir3+/4+) (V) L 0.57 0.91 - 1 0.48 0.87 1.88 aE 1/2 = 1/2(Epa + Epc), where E and Epc are the anodic and catho-dic peak potentials, respectively. Fig. 2: Cyclic voltammograms for ligand L and complex 1 in CH2Cl2 solution containing n-Bu4NClO4 (0.1 M) at a sweep rate of 100 mV/s 4. Conclusions In conclusion, a new iridium(III) complex 1 based on tetrathiafulvalene-substituted triazole-pyridine ligand, has been synthesized and fully characterized by 1H NMR, 13C NMR, mass spectrometry, FTIR and elemental analyses. The photophysical and electrochemical properties have been measured and analyzed. The luminescent spectra show that the emissive state originates from mixed intrali-gand and metal-to-ligand charge transfer 3(n^n* + MLCT) transitions. The electrochemical studies reveal that 1 undergo reversible TTF/TTF+/TTF2+ redox processes and one irreversible Ir3+^Ir4+ oxidation process. The research plays a role in designing new photoelectric functional materials, and more work is going on in our laboratory. 5. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 21501037), the Natural Science Foundation of Hainan Province (No. 20152031) and Hainan Provincial Innovation Experiment Program for University Students (No. 201511658002). 6. Supplementary Material 1H NMR, 13C NMR and ESI-MS spectra for iridium complex 1. 7. References 1. M. Bendikov, F. Wudl, D. F. Perepichka, Chem. Rev. 2004, 104, 4891-4945. http://pubs.acs.org/doi/abs/10.1021/cr030666m 2. S. Wenger, P. A. Bouit, Q. L. Chen , J. Teuscher, D. D. Censo, R. H. Baker, J. E. Moser, J. L. Delgado, N. Martin, S. M. Zakeeruddin, M. Grätzel, J. Am. Chem. Soc. 2010, 132, 5164-5169. http://pubs.acs.org/doi/abs/10.1021/ja909291h 3. F. G. Brunetti, J. L. López, C. Atienza, N. Martín, J. Mater. Chem. 2012, 22, 4188-4205. http://pubs.rsc.org/en/content/articlepdf/2012/jm/c2jm 15710a 4. D. Canevet, M. Sallé, G. X. Zhang, D. Q. Zhang, D. B. Zhu, Chem. Commun. 2009, 2245-2269. 5. Y. G. Sun, S. F. Ji, P. Huo, J. X. Yin, Y. D. Huang, Q. Y. Zhu, J. Dai, Inorg. Chem. 2014, 53, 3078-3087. 6. G. N. Li, L. R. He, L. Li, W. F. Cheng, X. Y. Li, H. H. Chen, Acta Chim. Slov. 2014, 61, 786-791. https://journals.matheo.si/index.php/ACSi/article/view/473 7. S. F. Ji, Y. G. Sun, P. Huo, W. C. Shen, Y. D. Huang, Q. Y. Zhu, J. Dai, Inorg. Chem. 2014, 53, 3611-3617. Niu et al.: New Iridium Complex Coordinated with Tetrathiafulvalene . 326 Acta Chim. Slov. 2016, 63, 323-326 8. J. Qin, L. Hu, N. Lei, Y. F. Liu, K. K. Zhang, J. L. Zuo, Acta Chim. Slov. 2014, 61, 740-745. https://journals.matheo.si/index.php/ACSi/article/view/443 9. D. Lorcy, N. Bellec, M. Fourmigué, N. Avarvari, Coordin. Chem. Rev. 2009, 253, 1398-1438. http://www.sciencedirect.com/science/article/pii/S0010854 508001768 10. G. N. Li, L. R. He, D. Xia, L. Li, W. F. Cheng, K. X. Li, F. Cui, Z. G. Niu, J. Chin. Chem. Soc. 2015, 62, 889-897. http://onlinelibrary.wiley.com/doi/10.1002/jccs.201500251 /abstract 11. K. R. J. Thomas, M. Velusamy, J. T. Lin, C. H. Chien, Y. T. Tao, Y. S. Wen, Y. H. Hu, P. T. Tai, Inorg. Chem. 2005, 44, 5677-5685. http://pubs.acs.org/doi/abs/10.1021/ic050385s 12. M. A. Baldo, C. Adachi, S. R. Forrest, Phys. Rev. B. 2000, 62, 10967-10977. http://journals.aps.org/prb/abstract/10.1103/PhysRevB.62. 10967#fulltext 13. J. M. Lupton, I. D. W. Samuel, M. J. Frampton, R. Beaving-ton, P. L. Burn, Adv. Funct. Mater. 2001, 11, 287-294. http://onlinelibrary.wiley.com/doi/10.1002/1616-3028C200 108)11:4%3C287::AID-ADFM287%3E3.0.C0;2-Z/abstract 14. Y. P. Zeng, C. W. Gao, L. J. Hu, H. H. Chen, G. Y. Chen, G. N. Li, Z. G. Niu, Acta Chim. Slov. 2015, 62, 917-922. https://journals.matheo.si/index.php/ACSi/article/view/1744 15. R. D. Costa, E. Orti, H. J. Bolink, S. Graber, S. Schaffner, M. Neuburger, C. E. Housecroft, E. C. Constable, Adv. Funct. Mater. 2009, 19, 3456-3463. http://onlinelibrary.wiley.com/doi/10.1002/adfm.200900911 /full 16. G. N. Li, Y. Liao, T. Jin, Y. Z. Li, Inorg. Chem. Commun. 2013, 35, 27-30. http://www.sciencedirect.com/science/article/pii/S13877003 13002153 17. S. Okada, K. Okinaka, H. Iwawaki, M. Furugori, M. Hashimoto, T. Mukaide, J. Kamatani, S. Igawa, A. Tsuboyama, T. Takiguchi, K. Ueno, Dalton Trans. 2005, 9, 15-83. http://pubs.rsc.org/en/content/articlehtml/2005/dt/b417058j 18. J Qin, S. Y. Deng, C. X. Qian, T. Y. Li, H. X. Ju, J. L. Zuo, J. Organomet. Chem. 2014, 750, 7-12. 19. Z. G. Niu, D. Liu, J. Zuo, J. M. Yang, Y. H. Su, Y. D. Yang, G. N. Li, Inorg. Chem. Commun. 2014, 43, 146-150. http://www.sciencedirect.com/science/article/pii/S13877003 14000872 20. L. Y. Zhang, G. F. Liu, S. L. Zheng, B. H. Ye, X. M. Zhang, X. M. Chen, Eur. J. Inorg. Chem. 2003, 2965-2971. http://onlinelibrary.wiley.com/doi/10.1002/ejic.200300061/ abstract 21. S. Bettington, M. Tavasli, M. R.Bryce, A. Beeby, H. A. Attar, A. P. Monkman, Chem. Eur. J. 2007, 13, 1423-1431. http://onlinelibrary.wiley.com/doi/10.1002/chem.200600888 /citedby 22. M. K. Nazeeruddin, R. T. Wegh, Z. Zhou, C. Klein, Q. Wang, F. D. Angelis, S. Fantacci, M. Grätzel, Inorg. Chem. 2006, 45, 9245-9250. http://pubs.acs.org/doi/abs/10.1021/ic060495e 23. G. N. Li, T. Jin, L. Sun, J. Qin, D. Wen, J. L. Zuo, X. Z. You, J. Organomet. Chem. 2011, 696, 3076-3085. http://www.sciencedirect.com/science/article/pii/S0022328 X11003676 Povzetek Sintetiziran in strukturno okarakteriziran je nov iridijev(III) kompleks [Ir(ppy)2(L)]PF6 (1) z vezanim triazol-piridin-skim ligandom modificiranim s tetratiafulvensko skupino. Absorpcijski in luminiscenčni spekter ter elektrokemijske lastnosti L in 1 so bili raziskani. Kompleks 1 emitira pri sobni temperature pri 481 in 510 nm. Široki in strukturirani emisijski trakovi so pripisani mešanju 3LC (3n-n*) in 3CT (3MLCT) vzbujenih stanj. Vpliv koordinacije iridijevega iona na redoks lastnosti TTF skupine je bil raziskan s pomočjo ciklične voltametrije. Niu et al.: New Iridium Complex Coordinated with Tetrathiafulvalene . DOI: 10.17344/acsi.2016.2269 Acta Chim. Slov. 2016, 63, 327-334 327 Scientific paper Indoor Nanoparticles Measurements in Workplace Environment: The Case of Printing and Photocopy Center Irena Grgic,1* Jožica Bratec1,2 and Marija Bester Rogač2 1 Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia 2 University of Ljubljana, Faculty of Chemistry and Chemical Technology, Večna pot 113, SI-1000 Ljubljana, Slovenia * Corresponding author: E-mail: irena.grgic@ki.si Received: 20-01-2016 Abstract In recent studies, laser printers and photocopy machines have been identified as important sources of indoor air pollution with fine and ultrafine particles. In this work, the indoor pollution of a printing and photocopy center in Ljubljana, Slovenia was investigated. The particle number concentration time series and the particle size distributions were measured continuously for a period of one month by a scanning mobility particle sizer (SMPS). Our measurements clearly showed that during operating hours the total number concentration of nanoparticles (size between 15 and 750 nm) increased in both working rooms with laser printers as well as in a room with photocopy machines. In rooms with laser printers the bimodal particle size distribution was frequently observed (i.e. max. at ca. 20 or 30 nm and at ca. 100 nm), with the aged particles persisted in the room over the night and over the weekend. In the photocopy room the situation was different, again with a sharp increase in concentration of small particles (ca 20 nm) and their growth to bigger sizes, but after closing a decrease to the background concentration. The results undoubtedly proved that the fast increase in na-noparticles (size below 50 nm) was associated with processes, the intense laser printing and photocopying activity. Our study also confirmed that the ventilation of the room is a very important factor which affects the life time of aged nano-particle in the indoor environment. Keywords: Indoor air quality, indoor environment, ultrafine and fine particles, laser printer emissions, photocopier emissions 1. Introduction Nowadays we spend the majority of our lifetime, professional and private, in different indoor environments. In addition to the influence of outdoor pollution, which can penetrate into the buildings, various different sources can contribute to indoor pollution. Electronic devices, such as personal computers, printers, photocopy machines, which are nearly vital in our lives, can importantly influence the indoor air quality. Therefore, the emissions from such devices are of big health concern. Many studies have reported that laser printers and photocopy machines emit besides volatile organic compounds (VOCs) and ozone, also fine and ultrafine particles.1-6 It is also known that the major fraction of particles emitted during operation of laser printers represents ultrafine particles (i.e. nanoparticles) with the size range below 100 nm with an average size of about 30-50 nm.7,8 The studies on indoor pollution due to the emissions of nanoparticles from laser printers and photocopy machi- nes are mostly related to the particle concentrations and size distributions1'9'10 and to possible formation mechanisms.810 Measurements on particle emissions in the real-room environment710 and studies on modeled office environment can be found as well;5 the influence of different parameters, such as fuser roller temperature on the emissions of laser printers was also studied.711 The majority of particles emitted from laser printers is volatile and of secondary nature, i.e. formed in the air through the reactions of VOCs and semi volatile organic compounds (SVOCs) originating from paper and/or hot toner with ozone.8 In addition, Barthel et al.12 reported on elemental analysis of fine and ultrafine particles, and the elements identified (e.g. Si, S, Cl, Ca, Ti, Cr, Fe) were mainly connected with toner and paper. Further, the studies have also pointed out the potential health hazards associated with nanoparticles emitted during laser printing and photocopying operation.13-15 For example, it has been shown that already short-term expo- Grgic et al.: Indoor Nanoparticles Measurements in Workplace 328 Acta Chim. Slov. 2016, 63, 327-334 sures (i.e. 6 h) to modest concentrations (5,000-30,000 particles cm-3) of nanoparticles emitted during photocopying induced statistically significant increases in systemic oxidative stress and upper airway inflammation.14 In addition, occupational and consumer risk for nanoparticles from laser printers have been estimated16 and their toxico-logical effects have been recognized by World Health Organization as well.17 In this work, the indoor pollution with fine and ultrafine particles in a company for spatial informatics and graphic design from Ljubljana, Slovenia dealing with different services, among which are also printing and photo-copynig, was investigated for the first time. The particle number concentrations and the particle size distributions were measured continuously in a period of one month in three working rooms (in each for about 10 days) where different hardcopy devices were in use. 2. Experimental 2. 1. Instrumentation A Scanning Mobility Particle Sizer spectrometer (SMPS 3936L75, TSI) was used for continuous measurements of submicrometer particle number concentrations and size distributions in the range from 15 nm to 750 nm (scan up time 180 s; retrace time 15 s). The SMPS consists of an Electrostatic Classifier with a long Differential Mobility Analyzer (DMA, 3081), negatively charged high voltage controller and Impactor nozzle (0.071 cm), which is coupled to a Condensation Particle Counter (CPC 3775). The solvent for the CPC was n-butanol (Reagent Grade). The SMPS was set to measure every 5 minutes during period from February 25 to March 28, 2014. A sample flow rate of 0.3 L min-1 was used with a sheath flow of 3 L min-1. 2. 2. Sampling Sites Measurements were performed in a company for spatial informatics and graphic design from Ljubljana, Slovenia in three different working rooms dealing with different kind of services (e.g. digital printing, graphic design, scanning, photocopying). From a schematic illustration (Figure 1) it can be seen that in the first working room (Room 1, size: 5.5 m x 7.2 m x 3.2 m) the SMPS stand on a table at 0.75 m from the ground with the sampling tube at a distance of about 2 m to the laser printer (Konika Minolta C7000); in this room was also one bigger inkjet plotter (Inkjet Cannon iPF8000S) at the distance of about 3 m to the SMPS. In the second room (Room 2, size: 10 m x 7.3 m x 3.20 m) the SMPS was about 3 m from the laser printer (Laser Xerox Colour 560) (Figure 1); there were also four bigger inkjet plotters of different producers (Roland Versa CAMM, Sure-Colour S 30610, Hp designjet 5500 and UV-160 UV printer Mimaki). In the third room (Room 3, size: 5.2 m x 7.5 m x 3.2 m) there were two photocopy machines (Ducacolors 252 and Kyocera mita, KM4530). The SMPS was in the corner on the shelf at about 0.75 m from the ground with the sampling tube at about 2-3 m to the machines (Figure 1). Figure 1: Schematic illustration of three investigated working rooms in a company for spatial informatics and graphic design in Ljubljana, Slovenia with denoted positions of SMPS in each room as well as printers and copiers. L: laser printer, P: photocopy machine and I: inkjet plotter. The continuous measurements were performed for one month, the first 10 days in Room 1 with one laser printer, then the SMPS was moved into Room 2 with one laser printer as well, and the last 7 days the measurements were performed in Room 3 with two photocopy machines (Figure 1). The ventilation in Room 1 and Room 3 was carried out only by opening the windows when necessary, mostly in the morning; while in Room 2 there was no window at all, the only access of fresh air, better said the mixing of the air was possible through the door between the two rooms. The working time from Monday to Thursday was from 8:00 to 17:00, on Friday from 8:00 to 16:00, while during the weekend the company was closed. 3. Results and Discussion 3. 1. Results of SMPS Measurements in Room 1 The continuous measurements of fine and ultrafine particles in the company for spatial informatics and graphic design from Ljubljana were started in the Room 1 (Figure 1) at 16:00 on February 25 and finished at 14:00 on March 6, 2014. The typical particle number size distribu- Grgic et al.: Indoor Nanoparticles Measurements in Workplace Acta Chim. Slov. 2016, 63, 327-334_ 329 tions for all days including the weekend are shown in Figu- immediately after 8:00. In most cases a bimodal size distri-re 2. In general, it is evident that the concentration of nano- bution was observed: first one is a mode with particles of a particles significantly increased during working hours, i.e. diameter at around 30 nm and the second one with partic- Figure 2: Number concentration (particle cm-3) and size distribution of the particles continuously measured in Rooml of the company of spatial informatics and graphic design in Ljubljana, Slovenia from February 25 to March 6, 2014. White color represents the concentrations above 10 X 103 particle cm-3. Grgic et al.: Indoor Nanoparticles Measurements in Workplace 330 Acta Chim. Slov. 2016, 63, 327-334 les between 50 and 150 nm (maximum at around 100 nm). Strong emissions of smaller particles can be undoubtedly seen especially on February 26, March 3 and March 4, 2014. Although the concentration of particles decreased during the nonworking time it is evident that they persisted in the room during the night and also during the weekend (March 1 and 2, 2014); these were mostly aged particles with the average particle size of around 100 nm. The characteristic total number concentration of particles between 15 and 750 nm measured on March 5, 2014 (Figure 3 a) show a clear diurnal variation; it can be seen that the concentration raised steeply after 8:00 in the morning, reached the highest concentration during the high load of work between 8:00 and 12:00, and decreased to below 3.0 x 103 particle cm-3 at 15:00. In the Room 1 the average total number concentration for all working days during the working hours (from 8:00 to 17:00) was around 5.1 x 103 particle cm-3, while the highest measured concentration during printing was around 17 x 103 particle cm-3 determined at 12:30 on March 6, 2014. Our measurements also reveal that the concentration of particles (i.e. background concentration) during nonworking time (no printing) was about 2 x 103 particle cm-3. Obviously, the elevated concentrations did not decrease always to the background concentration as it can be seen from the results over the night and also from the results for the weekend when the average concentration for Saturday March 1 was about 3.7 x 103 particle cm-3 and for Sunday even higher (ca. 4.6 x 103 particle cm-3). However, it can be assumed that these were aged particles of the size of about 100 nm (Figure 2) expressing higher concentrations after 18:00 in the evening until the next day morning. Observed situation can be ascribed to the absence of any ventilation during the weekend. In any case, the average number particle concentration in the Room 1 during working time was more than 2 times higher than during nonworking time, and the maximal measured number particle concentrations were more than 5 times higher than the background concentrations. 3. 2. Results of SMPS Measurements in Room 2 The SMPS was afterward moved into the Room 2 (Figure 1) where the continuous particle measurements were conducted from March 7 to March 17, 2014. From Figure 4 representing size-resolved particle number concentration time series for 10 days, it is evident that in general the indoor pollution with particles was similar as in Room 1, but still with some important differences. As in Room 1 the concentration of nanoparticles raised immediately in the morning when the laser printer and other electronic devices were turned on. During working days the bimodal size distribution was frequently observed, i.e. particles with a diameter below 50 nm (maximum at around 20 or 30 nm) and particles between 50 and 200 nm with maximum at around 100 nm (e.g. March 10 and 12, 2014 in Figure 4). The aging of particles was evident every working day; for example very clearly at around 14:00 on 4> o t ro Cl t E u [O 1 2E+ 04 c 2 h), high-temperature requirement (> 250 °C), use of toxic and expensive organic solvents (e.g. n-hexylamine), and use of surfactants (e.g. oleic acid, SDS and trioctylphosphine oxide). From a practical viewpoint, the development of a simple and new precursor for the synthesis of Co3O4 nanoparticles at lower temperatures and shorter reaction times is still an active area of research. In the present work, we wish to report on the direct thermolysis of an energetic pentamminecobalt(III) complex, [Co(NH3)5(H2O)](NO3)3, which led to the synthesis of Co3O4 nanoparticles at low temperature (175 °C) without needs expensive and toxic solvents or complicated equipment. The obtained Co3O4 nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-visible spectroscopy, and magnetic measurement. The method is a fast, mild, energy-efficient and environmentally friendly route to produce Co3O4 nanopar-ticles in only one step. 2. Experimental 2. 1. Preparation of [Co(NH3)5(H2O)](NO3)3 precursor The precursor [Co(NH3)5(H2O)](NO3)3 was synthesized according to the literature method.54 Briefly, 10 grams of carbonatopentamminecobalt (III) nitrate (0.036 mol) was suspended in 25 mL of water, and 20 mL of 1:l nitric acid and water solution was added with stirring. When the evolution of carbon dioxide has stopped (10 minutes), 100 ml. of ethanol is added. The red precipitate of aquopentam-minecobalt(II1) nitrate, [Co(NH3)5(H2O)](NO3)3, is collected on a paper filter, washed with alcohol and ether, and then dried in air. Yield: 86%. The composition of the complex was confirmed by thermal analysis, FT-IR, and elemental analysis: Anal. calc. for [Co(NH3)5(H2O)](NO3)3: Co, 16.93; H, 4.92; N, 32.19; found: Co, 16.84; H, 4.85; N, 32.08. 2. 2. Preparation of Co3O4 Nanoparticles In order to prepare Co3O4 nanoparticles, 2 g of the [Co(NH3)5(H2O)](NO3)3 complex powder in a porcelain crucible was placed in a muffle furnace. The sample was heated at the rate of 10 °C min-1 from room temperature to 150 °C in air and was maintained at this temperature for 1 h. Similar experiment was performed for the sample calcined at the selected temperature of 175 °C. The temperatures for calcining the complex were selected from the TG-DTA data (Figure 1). The black product generated from the complex at each temperature was cooled to room temperature and collected for characterization. 2. 3. Methods of Characterization Thermal analysis was conducted with a Netzsch STA 409 PC/PG thermal analyzer at a constant heating rate of 10 °C min-1 in air. The composition and phase purity of the products were characterized by a Rigaku D/max C III X-ray diffractometer using Ni-filtered Cu Ka radiation (X = 1.5406 A). XRD patterns were recorded in the 28 range of 10°-80° with a scanning step of 0.02°. To investigate chemical bonding of the products, infrared spectra were recorded on the diluted samples in KBr pellets using a Schimadzu 160 FT-IR spectrophotometer within the region of 4000-400 cm-1. The optical absorption spectrum was recorded on a Shimadzu 1650PC UV-vis spectropho-tometer in a wavelength range of 200-700 nm at room temperature. The samples for UV-vis studies were well dispersed in distilled water by sonication for 30 min to form a homogeneous suspension. The morphology of Co3O4 nanoparticles was studied with a Mira3 Tescan field emission scanning electron microscope. The particle sizes of the as-prepared product were observed with a transmission electron microscope (TEM, Philips CM10) and equipped with an energy dispersive X-ray spectros-copy. For the TEM measurements, the powders were ul-trasonicated in ethanol and a drop of the suspension was dried on a carbon-coated microgrid. Raman spectrum was obtained using a Thermo Fisher DXR with a laser wavelength of 780 nm and a spot size of 0.5 nm. The magnetic properties of Co3O4 nanoparticles were measured using a vibrating sample magnetometer (VSM, Iran Meghnatis Daghigh Kavir Company). 2. 4. Photocatalytic Tests 50 ml of 25 mg/L methylene blue (MB) aqueous solution was used for the photocatalytic experiment. 30 mg of the Co3O4 nanoparticles were added to MB aqueous solution and stirred with a magnetic stirrer in the dark for 30 min to establish adsorption-desorption equilibrium between the solution and catalyst prior to the irradiation from the 400 W high-pressure Mercury lamp (X > 420 nm). After adding 2 mL of 30% H2O2 to the suspension, the lamp was turned on. Samples were taken out and the changes of MB concentration were monitored using a UV-vis spectrometer. At regular time intervals, 5 ml MB aqueous solution was taken out from the reactor vessel and centrifuged to separate the solution and the suspended catalyst. The Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles Acta Chim. Slov. 2016, 63, 335-337 343 UV-vis adsorption spectrum of the filtered solution was measured in the range 400-800 nm. The degradation degree of MB in the aqueous solution was estimated by the absorbance measurements at about 665 nm. All the aqueous samples were at natural pH and all experiments were carried out at room temperature. 3. Results and Discussion 3. 1. Characterization of Co3O4 Nanoparticles Thermal behavior of the [Co(NH3)5(H2O)](NO3)3 precursor was studied by thermal analysis in the temperature range of 25-600 °C. The DTA and TG curves in Fig. 1 show the decomposition of complex proceeds in two stages. In first stage, a small endothermic peak occurred at about 100 °C and shows about 5.25% weight-loss which is consistent with the theoretical value of 5.17% caused by the loss of one molecule of H2O per one molecule of complex and the formation of [Co(NH3)5(NO3)](NO3)2.54 In second stage, the residue gives a sharp exothermic peak at about 175 °C with an extensive weight loss (72%) which related to the explosive decomposition of the complex via an intramolecular redox process occurring between the NH3 ligands as reducing agents and the NO3- ions as oxidizing agents. Above 175 °C, the weight remained constant, confirming the complete decomposition of the complex. The weight loss of two steps to be about 77.25% which is consistent with the theoretical value (76.95%) calculated for the formation of Co3O4 from the complex. Although the exact reaction is unclear and intermediates and gaseous products had not been identified directly, based on the above TG/DTA results and previously reported data,55,56 the explosive decomposition of the complex resulted in the solid Co3O4 and probably gaseous products (i.e. NH3, N2, NO, N2O and H2O) can be expressed as follows: 3[Co(NH3)5(H2O)](NO3)3 (s) ^ Co3O4 (s) + gaseous products (i.e. 2NH3 (g), 19.5H2O (g) + 9.25N2 (g) + 1.5NO (g) and ^O(g)) The FT-IR spectra of the [Co(NH3)5(H2O)](NO3)3 complex and its decomposition products at the selected temperatures were shown in Figure 2. As shown in Figure 2(a), the FT-IR spectrum of the complex shows the characteristic bands of the NH3 and NO3 groups ligands at about 3500-3000, 1600-1500, 1450-1250, 1050 and 650 cm-1.57 For the sample calcined at 150 °C in Figure 2(b), most of the bands associated with the complex disappeared and two weak bands of the spinel-type Co3O4 structure at about 660 and 560 cm-1 are observed. The former band is characteristic of Co3+-O vibration in an octahedral site, and the later one is attributable to the Co2+-O vibration in a tetrahedral site of the Co3O4 lattice.32 As can be seen in Figure 2(c), the sample decomposed at 175 °C shows only two characteristic bands of the Co3O4 phase, confirming the complete decomposition of the complex to pure Co3O4 phase. Figure 1. TG and DTA curves of the [Co(NH3)5(H2O)](NO3)3 complex. a) nh3+h2o NCH ^ NH-i J NH3+NO3 b) C03O4 C03O4 "■"■■"•'I"--------------1................-I— 4000 3000 2000 1000 Wavenumber (cm1) soo Figure 2. FT-IR spectra of (a) [Co(NH3)5(H2O)](NO3)3 complex and its decomposition product at (b) 150 °C and (c) 175 °C. Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles ... 338 Acta Chim. Slov. 2016, 63, 335-343 Figure 3 shows the XRD patterns of the samples calcined at 150 and 175 °C. The XRD pattern of sample decomposed at 150 °C in Figure 3(a) exhibits weak diffraction peaks with 29 values at 19.50°, 31.37°, 37.02°, 39.10°, 44.97°, 55.84°, 59.58°, 65.44° and 77.65°. These diffraction peaks can be indexed to the crystalline cubic phase Co3O4 with lattice constant of a = 8.076 A and a space group of Fd3m, which are in agreement with the reported values (JCPDS Card No. 76-1802). This result confirms that the Co3O4 phase started to appear at 150 °C, as indicated by the FT-IR result. As can be seen in Figure 3(b), the intensity of the characteristic peaks of the Co3O4 phase markedly increases with increasing the decomposition temperature to 175 °C. This finding confirms that the complex was completely decomposed to the Co3O4 phase at 175 °C. No impurity diffraction peaks were detected in the patterns, indicating that the product is of high purity. Furthermore, the diffraction peaks are markedly broadened due to the small size effect of the particles. The average sizes of the Co3O4 particles was calculated by the Deb-ye-Scherrer equation:58 Dxrd = 0.9X/(Pcos9) where Dxrd is the average crystalline size, X is the wavelength of Cu-Ka, P is the full width at half maximum (FWHM) of the diffraction peak and 9 is the Bragg's angle. The average size of the nanopartricles calculated using the most intense peak (311) at 29 = 36.26° is approximately 20 nm. This value is in accordance with TEM observations (discussed below). a) i^' c b) 175 °C o fN LU, o ? 10 20 30 40 50 60 70 80 20 (degree) Figure 3. The XRD patterns for the decomposition product of [Co(NH3)5(H2O)](NO3)3 complex at (a) 150 °C and (b) 175 °C. It is known that Raman scattering is very sensitive to the microstructure of nanocrystalline materials, it is also used here to clarify the structure of the Co3O4 nanopartic-les. As shown in Fig. 3, the Raman spectrum of the Co3O4 nanoparticles in the range of 400-800 nm shows four obvious peaks located at around 467, 508, 610, and 675 cm-1, corresponding to the four Raman-active modes of Co3O4. The Raman bands with medium intensity located at 467 and 508 cm-1 have the Eg and F2g(2) symmetry, respectively, whereas the weak band located at 610 cm-1 has the F2g(1) symmetry.40 The strong band at about 675 cm-1 is attributed to the characteristics of the octahedral sites (CoIIIO6), which is assigned to the A1g species in the Oh spectroscopic symmetry [40]. The Raman shifts are consistent with those of pure crystalline Co3O4, indicating that the Co3O4 nanoparticles have a similar crystal structure of the bulk Co3O4. 59 However, compared with that for bulk Co3O4, the peak positions of the four active modes of Eg, F2g(2), F2g(1) and A1g shift to low wavenumbers about 15, 13, 6 and 16 cm-1, respectively.59 This phenomenon is attributed to the optical phonon confinement effect in nano-structures that can cause uncertainty in the phonon wave vectors and then a downshift of the Raman peaks.60 Figure 4. Raman spectrum of the Co3O4 nanoparticles. The morphology of Co3O4 nanoparticles was investigated by SEM. Figure 5 shows the SEM image of the as-prepared Co3O4 nanoparticles. From the SEM image, it is clearly evident that the product consists of extremely fine particles with sphere-like morphologies that appreciably aggregated as clusters due to the extremely small dimensions and high surface energy of the obtained nano-particles. The SEM image shows irregular particle agglomerates of the product, indicating that the synthesized Co3O4 is actually composed of numerous nanoparticles with a uniform size, and these particles undergo further aggregation to form porous agglomerate structure. The TEM image and size distribution of the Co3O4 nanoparticles are shown in Figure 6. The TEM sample was prepared by dispersing the powder in ethanol by ultrasonic vibration. It can be seen from Figure 6(a) that the nanoparticles show approximately sphere-like morphologies with a uniform size. Because of the small dimensions Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles Acta Chim. Slov. 2016, 63, 335-339 343 Figure 5. SEM image of the Co3O4 nanoparticles. and high surface energy of the particles, it is easy for them to aggregate as seen in Figure 6(a). We also can find from this figure that the morphology of the particles is almost homogeneous. To investigate the size distribution of the Co3O4 nanoparticles, the particle size histogram was also determined from the TEM image. Figure 6(b) shows the particle size distribution of the Co3O4 particles. It is clear that the diameter sizes of the Co3O4 nanoparticles are approximately in the range of 5 to 30 nm with a narrow size distribution. The average particle size is 17.5 nm, which is in agreement with the result calculated for the half-width of diffraction peaks using the Scherrer's formula, allowing for experimental error. The chemical purity and stoichiometry of the product were also examined by EDX analysis. Figure 7 shows the EDX spectrum of the Co3O4 nanoparticles prepared by the decomposition of [Co(NH3)5(H2O)](NO3)3 at Figure 7. EDX spectrum of the Co3O4 nanoparticles. 175 °C. Only oxygen and cobalt elements existed in the product. The atomic percentages of Co and O were found to be 43.14% and 56.86%, respectively, which is near to the theoretical ratio (3:4) of Co3O4. The Au peaks at about 2.2 and 9.75 keV correspond to the TEM holding grid. No other elements can be detected, indicating the high purity of the Co3O4 nanoparticles. To determine the magnetic properties, the hysteresis loop of the Co3O4 nanoparticles was measured at room temperature. As shown in Figure 8, the magnetization is approximately linear with the field and it does not attain the saturation even at the applied field of 8 kOe. As shown in the inset of Figure 8, a tiny hysteresis loop can be observed with a coercivity of about 135 Oe which is characteristic of weak ferromagnetic behaviour, although bulk Co3O4 has antifer- a) b) ■ 10 i-115 20 ■ m 25 30 Figure 6. (a) TEM image of the Co3O4 nanoparticles and (b) Histogram showing the size distribution of the Co3O4 nanoparticles Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles ... 340 Acta Chim. Slov. 2016, 63, 335-343 Figure 8. (a) Magnetization curve as a function of applied magnetic field for Co3O4 nanoparticles at room temperature, and (b) the expansion of magnetization vs. field near the lower applied field. romagnetic nature. This behavior is similar to that of Co3O4 nanoparticles obtained by a solvothermal process27 and may be explained by uncompensated surface spins and/or finite size effects of the Co3O4 nanoparticles.60 Optical absorption properties of the as-prepared Co3O4 nanoparticles were investigated at room temperature by UV-vis spectroscopy. As can be seen in Figure 9, the product shows two absorption bands in the wavelength ranges of 200-350 and 380-600 nm. As has been reported in the literatures,16,30 these bands can be assigned to the O2- ^ Co2+ and O2- ^ Co3+ charge transfer processes, respectively. Co3O4 is a p-type semiconductor and its band gap, Eg, can be determined by the following equation: (ahv)2 = K(hv-£ ) (1) Where hv is the photon energy (in eV), a is the absorption coefficient, K is a constant relative to the material. The plot of (ahv)2 versus hv is shown in the inset of Figure 9. The value of hv extrapolated to (ahv)2 = 0 gives an absorption band gap energy (Eg). The absorption bands in Figure 9 yield two Eg values of 3.45 and 2.20 eV for the product which are greater than the bulk Co3O4 values (2.19 and 1.48 eV, respectively).61 The increase in the band gaps of the Co3O4 nanoparticles supports a quantum confinement effect relating to tiny nanoparticles.62,63 3. 2. Photocatalytic Activity of the Co3O4 Nanoparticles The photocatalytic activity of the as-synthesized Co3O4 nanoparticles for the degradation of organic dye such as methylene blue (MB) has been performed under visible light irradiation at room temperature. The UV-vis spectra of MB aqueous solution in the presence of Co3O4 nanoparticles photocatalyst and H2O2 under visible light irradiation (X > 420 nm) over various time intervals are shown in Figure 10. MB dye has a characteristic absorption peak at about 662 nm, which obviously decreases with the increase of irradiation time due to the continuous photocatalytic degradation of MB molecules in the system. After 150 min irradiation, the absorbance of the MB aqueous solution reaches to less than 0.01, indicating the complete degradation of MB. Therefore, the photocataly-tic experiments show that the as-prepared Co3O4 nanopar-ticles have much high visible-light photocatalytic activity. 1 -T 1 3 to * u C « I 0.6 w A < 0.4 0.2 0.0 400 _ irradiation time (min) / ■ 0 1 30 60 90 / / 120 // r 150 // ■ P \ 1 ■ \ \ \\ 500 600 700 Wavelength (nm) 800 Figure 9. UV-Vis spectrum and (ahv)2-hv curve (inset) of the Co3O4 nanoparticles. Figure 10. Evolution of UV-vis absorption spectrum of methylene blue (MB) under irradiation at different times using Co3O4 nanoparticles in the presence of H2O2. Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles Acta Chim. Slov. 2016, 63, 335-341 343 Figure 11 shows the degradation rate of MB dye at different exposure times in the presence Co3O4 catalyst. C0 is the concentration of dye after the adsorption-desorption equilibrium but before irradiation, and C is the concentration of dye after different visible light irradiation times. As can be seen in Figure 11, in the absence of Co3O4 nearly 15% of the MB molecules are degraded by H2O2 after irradiation for 150 min (curve a). The degradation rate of MB molecules is significantly enhanced when Co3O4 is added to the dye solution (curve b). Nearly 100% of MB is degraded by Co3O4 nanoparticles in the presence of H2O2 after irradiation for 150 min. These results can be possibly attributed to the remarkable function of Co3O4 nanoparticles, which serve as generator of hydroxyl radicals (OH) via photoelectrochemical decomposition of H2O2 under visible light irradiation. Therefore, the as-synthesized Co3O4 nanoparticles are an excellent photoca-talyst in the presence of H2O2 under visible light irradiation to degrade organic dyes. 4. Conclusions In conclusion, Co3O4 nanoparticles with an average particle size of 17.5 nm have been successfully prepared by the thermal decomposition of the [Co(NH3)5(H2O)](NO3)3 as a new precursor at 175 °C. The formation of the Co3O4 nanoparticles from the precursor complex can be explained through a redox reaction between the NH3 ligands as the reducing agent and the NO3 ions as the oxidizing agent. This method yields sphere-like Co3O4 nanoparticles with a narrow size distribution and a weak ferromagnetic behavior. The estimated optical absorption band gaps of the Co3O4 nanoparticles are relatively blue-shifted, compared with the values for the bulk sample. The as-prepared Co3O4 nanoparticles exhibit an excellent photocatalytic activity for the H2O2-assisted degradation of MB dye under visible light irradiation. 5. Acknowledgements Figure 11. Photocatalytic degradation of MB in the presence of : (a) H2O2 and (b) Co3O4 + H2O2. Based on the above results, a possible photocatalytic mechanism of Co3O4 nanoparticles has been proposed as follows: Upon irradiation with visible light, Co3O4 nano-particles particles undergo charge separation, electrons in the valence band of Co3O4 can be excited to its conduction band (e-CB), causing the generation of holes in the valance band (h+VB) simultaneously (reaction 1). Then, the e-CB can activate the H2O2 to generate the OH and OH- (reaction (2)). Thus, the OH' generated from reaction (2) is the main factor for photodegradation of the dye. Co3O4 + hv ^ e CB + h+VB H2O2 + e CB ^ OH + OH- MB + OH ^ degradation products (CO2, H2O, NO3, etc) (2) (3) (4) The authors are grateful to the Lorestan University Research Council and Iran Nanotechnology Initiative Council (INIC) for financial support. 6. References 1. K. J. Klabunde, R. M., Nanoscale Materials in Chemistry, 2nd edn. Wiley, New York, 2012. 2. W. Y. Li, L. N. Xu, J. Chen, Adv. Funct. Mater. 2005, 15, 851- 857. http://dx.doi.org/10.1002/adfm.200400429 3. R. Wu, J. Wu, M. Yu, T. Tsai, C. Yeh, Sens. Actu. B: Chem. 2008, 131, 306-312. http://dx.doi.org/10.1016/j.snb.2007.11.033 4. A. Askarinejad, M. Bagherzadeh, A. Morsali, Appl. Surface Sci. 2010, 256, 6678-6682. http://dx.doi.org/10.1016Zj.apsusc.2010.04.069 5. T. E. Davies, T. Garcia, B. Solsona, S. H. Taylor, Chem. Commun. 2006, 32, 3417-3419. http://dx.doi.org/10.1039/B606973H 6. V. R. Mate, M. Shirai, C. V. Rode, Catal. Commun.. 2013, 33, 66-69. http://dx.doi.org/10.1016/j.catcom.2012.12.015 7. T. Maruyama, S. Arai, J. Electrochem. Soc. 1996, 143, 1383-1386. http://dx.doi.org/10.1149/L1836646 8. N. Du, H. Zhang, B. D. Chen, J. B. Wu, X. Y. Ma, Z. H. Liu, Y. Q. Zhang, D. R. Yang, X. H. Huang, J. P. Tu, Adv. Mater. 2007, 19, 4505-4509. http://dx.doi.org/10.1002/adma.200602513 9. X. W. Lou, D. Deng, J. Y. Lee, L. A. Archer, Adv. Mater. 2008, 20, 258-262. http://dx.doi.org/10.1002/adma.200702412 10. S. L. Chou, J. Z. Wang, H. K. Liu, S. X. Dou, J. Power Sources 2008, 182, 359-364. http://dx.doi.org/10.1016/jjpowsour.2008.03.083 11. Y. G. Li, B. Tan, Y. Y. Wu, Nano Lett. 2008, 8, 265-270. Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles ... 342 Acta Chim. Slov. 2016, 63, 335-343 http://dx.doi.org/10.1021/nl0725906 12. R. M. Wang, C. M. Liu, H. Z. Zhang, C. P. Chen, L. Guo, H. B. Xu, S. H. Yang, Appl. Phys. Lett. 2004, 85, 2080-2082. http://dx.doi.Org/10.1063/1.1789577 13. S. A. Makhlouf, J. Magn. Magn. Mater. 2002, 246, 184-190. http://dx.doi.org/10.1016/S0304-8853(02)00050-1 14. X. Lou, J. Han, W. Chu, X. Wang, Q. Cheng, Mater. Sci. Eng. B 2007, 137, 268-271. http://dx.doi.org/10.1016/j.mseb.2006.12.002 15. T. Warang, N. Patel, A. Santini, N. Bazzanella, A. Kale, A. Miotello, Appl. Catal. A: Gen. 2012, 423- 424, 21- 27. 16. L. Sun, H. Li, L. Ren, C. Hu, Solid State Sci. 2009, 11, 108112. http://dx.doi.org/10.1016/j.solidstatesciences.2008.05.013 17. Y. Chen, Y. Zhang, S. Fu, Mater. Lett. 2007, 61, 701-705. http://dx.doi.org/10.1016/j.matlet.2006.05.046 18. T. Lai, Y. Lai, C. Lee, Y. Shu, C. Wang, Catal. Today 2008, 131, 105-110. http://dx.doi.org/10.1016Zj.cattod.2007.10.039 19. W. W. Wang, Y. J. Zhu, Mater. Res. Bull. 2005, 40, 19291935. http://dx.doi.org/10.1016/j.materresbull.2005.06.004 20. L. Li, Y. Chu, Y. Liu, J. L. Song, D. Wang, X.W. Du, Mater. Lett. 2008, 62, 1507-1510. http://dx.doi.org/10.1016/j.matlet.2007.09.012 21. J. Du, L. Chai, G. Wang, K. Li, Y. Qian, Aust. J. Chem. 2008, 61, 153-158. http://dx.doi.org/10.1071/CH07186 22. R. M. Wang, C. M. Liu, H. Z. Zhang, C. P. Chen, L. Guo, H. B. Xu, S. H. Yang, Appl. Phys. Lett. 2004, 85, 2080-2082. http://dx.doi.org/10.1063/L1789577 23. Y. Li, J. Zhao, Y. Dan, D. Ma, Y. Zhao, S. Hou, H. Lin, Z. Wang, Chem. Eng. J. 2011, 166, 428-434. http://dx.doi.org/10.1016/j.cej.2010.10.080 24. H. Sun, M. Ahmad, J. Zhu, Electrochim. Acta 2013, 89, 199205. http://dx.doi.org/10.1016/j.electacta.2012.10.116 25. M. Ren, S. Yuan, L. Su, Z. Zhou, Solid State Sci. 2012, 14, 451-455. http://dx.doi.org/10.1016/j.solidstatesciences.2012.01.011 26. L. X. Yang, Y.J. Zhu, L. Li, L, Zhang, H. Tong, W. W. Wang, Eur. J. Inorg. Chem. 2006, 23, 4787-4792. http://dx.doi.org/10.1002/ejic.200600553 27. J. Ma, S. Zhang, W. Liu, Y. Zhao, J. Alloys Compd. 2010, 490, 647-651. http://dx.doi.org/10.1016/joallcom.2009.10.126 28. E. Lester, G. Aksomaityte, J. Li, S. Gomez, Prog. Cryst. Growth Charact. Mater. 2012, 58, 3-13. http://dx.doi.org/10.1016/j.pcrysgrow.2011.10.008 29. J. Jiu, Y. Ge, X. Li, X, L. Nie, Mater. Lett. 2002, 54, 260263. http://dx.doi.org/10.1016/S0167-577X(01)00573-0 30. F. Gu, C. Li, Y. Hu, L. Zhang, J. Cryst. Growth 2007, 304, 369-373. http://dx.doi.org/10.1016/jjcrysgro.2007.03.040 31. M. C. Gardey-Merin, O. M. Palermo, R. Belda, M. E. Fernández de Rapp, G. E.Lascalea, P. G. Vázquez, Proced. Mater. Sci. 2012, 1, 588-593. http://dx.doi.org/10.1016/j.mspro.2012.06.079 32. L. H. Ai, J. Jiang, Powder Tech. 2009, 195, 11-14. http://dx.doi.org/10.1016/j.powtec.2009.05.006 33. L. Li, J. Ren, Mater. Res. Bull. 2006, 41, 2286-2290. http://dx.doi.Org/10.1016/j.materresbull.2006.04.022 34. A. S. Bhatt, D. K. Bhat, C. W. Tai, M. S. Mater. Chem. Phys. 2011, 125, 347-350. http://dx.doi.Org/10.1016/j.matchemphys.2010.11.003 35. M. E. Baydi, G. Poillerat, J. L. Rehspringer, J. L. Gautier, J. F. Koenig, P. Chartier, J. Solid State Chem. 1994, 109, 281-288. http://dx.doi.org/10.1006/jssc.1994.1105 36. D. Y. Kim, S. H. Ju, H. Y. Koo, S. K. Hong, Y. C. Kangf, J. Alloys Compd. 2006, 417, 254-258. http://dx.doi.org/10.1016/joallcom.2005.09.013 37. R. V. Kumar, Y. Diamant, A. Gedanken, Chem. Mater. 2000, 12, 2301-2305. http://dx.doi.org/10.1021/cm000166z 38. K. Sinko, G. Szabo, M. Zrinyi, J. Nanosci. Nanotechnol. 2011, 11, 1-9. http://dx.doi.org/10.1166/jnn.2011.3875 39. D. Zou, C. Xu, H. Luo, L. Wang, T. Ying, Mater. Lett. 2008, 62, 1976-1978. http://dx.doi.org/10.1016Zj.matlet.2007.10.056 40. J. Jiang, L. Li, Mater. Lett. 2007, 6, 4894-4896. http://dx.doi.org/10.1016/j.matlet.2007.03.067 41. S. Fan, X. Liu, Y. Li, E. Yan, C. Wang, J. Liu, Y. Zhang, Mater. Lett. 2013, 91, 291-293 http://dx.doi.org/10.1016/j.matlet.2012.10.008 42. E. Traversa, M. Sakamoto, Y. Sadaoka, Part. Sci. Technol. 1998, 16, 185-214. http://dx.doi.org/10.1080/02726359808906794 43. S. Farhadi, N. Rashidi, Polyhedron 2010, 29, 2959-2965. http://dx.doi.org/10.1016/j.poly.2010.08.019 44. S. Farhadi, Z. Roostaei-Zaniyani, Polyhedron 2011, 30, 1244-1249. http://dx.doi.org/10.1016/j.poly.2011.01.028 45. M. Salavati-Niasari, F. Davar, Mater. Lett. 2009, 63, 441443. http://dx.doi.org/10.1016/j.matlet.2008.11.023 46. M. Y. Masoomi, A. Morsali, Coord. Chem. Rev. 2012, 256, 2921-2943. http://dx.doi.org/10.1016/j.ccr.2012.05.032 47. L. Ren, P. Wang, Y. Han, C. Hu, B. Wei, Mater. Phys. Lett. 2009, 476, 78-83. 48. F. Mohandes, F. Davar, M. Salavati-Niasari, J. Magn. Magn. Mater. 2010, 322, 872-877. http://dx.doi.org/10.1016/j.jmmm.2009.11.019 49. M. Salavati-Niasari A. Khansari, F. Davar, Inorg. Chim. Acta 2009, 362, 4937-4942. 50. K. Thangavelu, K. Parameswari, K. Kuppusamy, Y. Haldo-rai, Y, Mater. Lett. 2011, 65, 1482-1484. http://dx.doi.org/10.1016/j.matlet.2011.02.047 51. S. Farhadi, J. Safabakhsh, J. Alloys Compd. 2012, 515, 180185. http://dx.doi.org/10.1016/jjallcom.2011.11.135 52. S. Farhadi, K. Pourzare, Mater. Res. Bull. 2012, 47, 15501556. http://dx.doi.org/10.1016/j.materresbull.2012.02.028 53. S. Farhadi, K. Pourzare, Polyhedron 2014, 67, 104-110. http://dx.doi.org/10.1016/j.poly.2013.08.069 54. G. Schlesssinger, Inorg. Synth. 1953, 4, 171-174. http://dx.doi.org/10.1002/9780470132357.ch56 55. W. W. Wendlandt, J. Inorg. Nucl. Chem. 1963, 25, 545-551. http://dx.doi.org/10.1016/0022-1902(63)80239-0 56. M. Liszka-Skoczylas, E. Mikuli, J. Szklarzewicz, J. Het-manczyk, Thermochim. Acta 2009, 496, 38-44. Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles Acta Chim. Slov. 2016, 63, 335-343 343 http://dx.doi.org/10.1016/j.tca.2009.06.017 57. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Part B: Applications in Coordination, Organometallic, and Bioinorganic Chemistry, sixth ed., Wiley, New York, 2009. 58. H. P. Klug, L. E. Alexander, X-ray Diffraction Procedures, second ed., Wiley, New York, 1964. 59. V. G. Hadjiev, M. N. Iliev, I. V. Vergilov, J. Phys. C: Solid State Phys. 1988, 21, L199-L201. http://dx.doi.org/10.1088/0022-3719/21/7Z007 60. M. Han, W. Zhang, N. Shi, J. Li, Z. Xu, Chin. J. Inorg. Chem. 2008, 24, 797-802. 61. Y. Qi, Y. Zhao, Z. Wu, Mater. Chem. Phys. 2008, 110, 457462. http://dx.doi.Org/10.1016/j.matchemphys.2008.03.001 62. X. P. Shen, H. J. Miao, H. Zhao, Z. Xu, Appl. Phys. A: Mater. Sci. Process 2008, 91, 47-51. http://dx.doi.org/10.1007/s00339-007-4361-6 63. P. Deka, R. C. Deka, P. Bharali, New J. Chem., 2016, 40, 348-357. http://dx.doi.org/10.1039/C5NJ02515J Povzetek Raziskovali smo termični razpad trdnega prekurzurja [Co(NH3)5(H2O)](NO3)3. S termično analizo (TG/DTA) smo ugotovili, da pri razmeroma nizkih temperaturah (175 °C) kompleks razpade do nanodelcev Co3O4 brez uporabe toksičnih topil ali zapletene opreme. Dobljeni produkt smo karakterizirali z rentgensko praškovno difrakcijo (XRD), infrardečo spektroskopijo (FT-IR), Ramansko spektroskopijo, vrstično elektronsko mikroskopijo (SEM), presevno elektronsko mikroskopijo (TEM) energijsko disperzivno rentgensko spektroskopijo (EDX). Optične in magnetne lastnosti produkta pa smo preučevali z UV-Vis spektroskopijo in magnetometer z vibrirajočim vzorcem (VSM). Na podlagi rezultatov FT-IR, XRD in EDX analiz smo ugotovili, da je dobljeni product zelo čist Co3O4, s kubično spinelno strukturo. SEM in TEM posnetki kažejo, da imajo nanodelci Co3F4 sferično morfologijo. Optični absorpcijski spektri nanodelcev Co3F4 so pokazali dve energijski špranji (band gap) pri 2,20 eV in 3,45 eV, s čimer smo tudi potrdili polprevodniške lastnosti materiala. Magnetne meritve so pokazale šibko feromagnetno ureditev pri sobni temperature. S fotokatalitičnim razpadom barvila metilen modro smo prikazali, da imajo tako pripravljeni nanodelci Co3O4 dobro fotokatalitično aktivnost. Farhadi et al.: Characterization of Cobalt Oxide Nanoparticles ... 344 Acta Chim. Slov. 2016, 63, 344-350 DOI: 10.17344/acsi.2016.2322 Scientific paper Stereoselective Synthesis of Southern Fragment of Hantupeptin A Avula Srinivas,* Malladi Sunitha and Chakunta Govind Rao Department of Chemistry, Vaagdevi Degree & PG CollegeKishanpura, Warangal, Telangana, India 506001 * Corresponding author: E-mail: avula.sathwikreddy@ gmail.com Received: 04-02-2016 Abstract The stereoselective synthesis of the southern fragment (C21-C41) of Hantupeptin A is described. The required stereochemistry of P-hydroxy-a-methyl acid unit was accomplished through the Aldol reaction using Evan's chiral auxiliary followed by the installation of the terminal alkyne with Ohira-Bestmann reagent. Keywords: Hantupeptin A, Aldol Reaction, Stereoselective synthesis, Peptide; Evan's auxiliary 1. Introduction Novel bioactive metabolites are emerging as an important source of pharmacologically active compounds or promising lead structures in drug discovery.1-5 Naturally occurring cyclic peptides6 have come within this class possessing diverse biological activities like immunosup-pressant, antibiotic, antifungal, anti-inflammatory and anticancer effects.7 Indeed, marine organisms such as algae, sponges, and coelenterates became an exceptional source of these natural products. Since the discovery of the di-demnins, this class of natural products continues to stimulate active research in synthetic and medicinal chemistry, as well as in clinical oncology and cell biology.8 In 2009, Tan and co-workers have isolated a new cyclodepsipepti-de, hantupeptin A (1) from the marine cyanobacterium Lyngbya majuscula. The hantupeptin A (1) has exhibited cytotoxicity against MOLT-4 leukemia cells and MCF-7 breast cancer cells with IC50 values of 32 and 4.0 pM, res-pectively.9 The extensive spectral studies and advanced chiral techniques have revealed the planar structure as well as the absolute configuration of 1. Structurally, compound 1 is a 19-membered cyclic tetrapeptide, which consists of ?ve a-amino/hydroxy acid residues, including phenyl lactic acid, proline, N-methylvaline, valine, N-methylisoleucine and a a-methyl-P-hydroxy acid unit with an alkyne at the terminal end of the molecule. The stereochemistry at the hydroxyl group attached carbon (C-35) of an unusual hydroxy acid, 3-hydroxy-2-methyloctynoic acid (Hmoya) unit 4 was determined as S using the Mosher's analysis. However, the stereochemi- Srinivas et al.: Stereoselective Synthesis of Southern Fragment ... stry at the methyl group attached carbon (C-34) was not reported at that point of time. Later, in 2010, the same group has isolated hantu-peptins B (2) and C (3) along with 1 from the organic extracts of the same marine cyanobacterium.10 The only structural difference among these molecules is the degree of unsaturation in the unusual amino acid part, where 1 is having a terminal alkyne functionality, 2 has an alkene and 3 is without any unsaturation in its structure (Figure 1). Compounds 2 and 3 also showed moderate in vitro cytotoxicity against MOLT-4 (leukemic) and MCF-7 (breast cancer) cell lines. In the study of the re-isolation of compound 1, the relative stereo chemistry at C-34 carbon of Hmoya unit was determined as R by the rigorous NMR experiments. Very recently, the absolute configuration of Figure 1: Structures of Hantupeptins A-C. Acta Chim. Slov. 2016, 63, 344-350 345 Hmoya unit of hantupeptin C (3) was assigned as (2R,3S) based on the retention times of the Mosher ester derivative standards by RPLC-MS.11 Till date, no synthetic efforts have been reported in the literature for these molecules. In continuation of our interest on the synthesis of biologically active molecules,12 we have reported the synthesis of hantupeptin A C21-C41 fragment with the unusual component, Hmoya residue as a part of it. The Hmoya unit 4 is also present in a number of marine-derived compounds, such as onchidin B, kulomo'opunalide-1, kulomo'opuna-lide-2, and trungapeptin A. 2. Results and Discussion From the retrosynthetic outlook (Scheme 1), the desired molecule was envisioned to be obtained from the key intermediate 5, which, in turn may be built from 6 through oxidation followed by Ohira-Bestmann reaction. Compound 6 could be obtained by coupling compound 7 with an amine, derived from compound 8. The stereocen-tres in compound 7 could be achieved through Evan's syn aldol protocol followed by a reductive etherification. The stereochemistry in compound 8 was achieved from the natural amino acids L-isoleucine and L-valine. Preparation of the acid 7. The synthesis began with Evan's aldol reaction between the aldehyde 10 and oxazolidinone 9. Aldehyde 10 was prepared in two steps from the inexpensive 1,5-pentanediol following the reported procedure.13 The other, desired (^)-4-benzyl-3-pro-pionyloxazolidin-2-one 9 was also smoothly obtained using well documented literature protocol.14 The di-«-butyl-boron triflate mediated Aldol reaction between compounds 9 and 10 furnished the ^«-product 11 in 83% yield (Scheme 2). Protection of the secondary hydroxy group of the compound 11 as TBS-ether 12 was achieved in 87% yield by exposing to TBSCl/Imidazole in CH2Cl2 at room temperature for 18 h. Compound 12 was then treated with sodium borohydride in THF/pH 7 buffer at room temperature for the reductive removal of the auxiliary to provide alcohol 13. The primary hydroxyl group of compound 13 was oxidized to a carboxylic acid using (bisacetoxyiodo)benzene (BAIB) / 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) in CH2Cl2/pH 7 buffer to obtain the acid fragment 7 in 89% yield. Preparation of compound 8. The synthesis of compound 8 was commenced by carrying out the preparation of the known N-(ieri-butoxycarbonyl)-N-methyl-L-isoleu-cine 14 from L-isoleucine using the literature procedure.15 Esterification of the acid 14 with allyl bromide was clean- Srinivas et al.: Stereoselective Synthesis of Southern Fragment 35G Acta Chim. Slov. 2016, 63, 344-35G Scheme 2: Synthesis of the acid fragment 7. ly achieved by using K2CO3 in DMSO solvent at room temperature, to get the ester 15 in 80% yield. The required amide 8 was prepared from 15 by two transformations. First treating with TFA in CH2Cl2 to get secondary amine in good yields and used as such for the next step without further purification. Later, the crude amine, prepared from 15 was coupled with (tert-butoxycarbonyl)-L-valine under standard reaction conditions in the presence of 1-hydroxy-7-azabenzotriazole (HOAt) and 1-[bis(dimethylamino) methylene]-1H-1,2,3-triazolo[4,5-ft]pyridinium-3-oxide hexafluorophosphate (HATU) as coupling agents and N,N-diisopropyl ethylamine (DIPEA) as the base in anhydrous CH2Cl2 as the solvent at room temperature for 8 h to acquire the desired dipeptide fragment 8 in 84% yield (Scheme 3). Construction of C21-C41 segment from 7 and 8. With the successful completion of the desired fragments 7 and 8, the attention was turned to couple them to give the di-amide 16. For that, intially the boc protection of compound 8 was removed by using TFA in CH2Cl2 at 0 °C and then coupled with the compound 7 under HATU/HOAt conditions at room temperature, to obtain the required product 16 in 85% yield. The resulting compound 16 was hydrolyzed with potassium carbonate in methanol to give the primary alcohol 6 in 75% yield which upon the oxidation with TPAP/NMO to the aldehyde followed by the treatment with Ohira-Bestmann reagent gave the targeted terminal alkyne product 5 in 92% yield (Scheme 4). Scheme 3: Synthesis of the fragment 8. Scheme 4: Construction of the C21-C41 building block. Srinivas et al.: Stereoselective Synthesis of Southern Fragment Acta Chim. Slov. 2016, 63, 344-350 347 3. Experimental NMR spectra were recorded in CDCl3 on Bruker AM-300 (300 MHz) spectrometer at ambient temperature. Chemical shifts are reported in ppm relative to TMS as internal standard and coupling constants are reported in Hz. FTIR spectra were recorded on a Nicolet FT-IR 400 spectrometer in KBr or as neat. Optical rotations were measured on an Perkin-Elmer 141 polarimeter by using a 2 mL cell with a path length of 1 dm with CHCl3 or CDCl3 as solvent. Low resolution mass spectra were obtained on VG 70-70H or LC/MSD trap SL spectrometer operating at 70 eV using direct inlet system. High resolution mass spectra (HRMS) were recorded on an Agilent Technologies 6510 Q-TOF spectrometer. Technical-grade EtOAc and hexanes used for column chromatography were distilled before use. All the reagents and solvents were of reagent grade and used without further purification unless otherwise stated. (5S,6fl)-7-((fl)-4-Benzyl-2-oxooxazolidm-3-yl)-5-hydro xy-6-methyl-7-oxoheptyl benzoate (11): To a stirred solution of acyl oxazolidinone 914 (1.04 g, 4.45 mmol) in CH2Cl2 (10 mL) was added dropwise n-Bu2BOTf (1.0 M in CH2Cl2, 4.67 mL, 4.67 mmol) and stirred for 10 min. i-Pr2NEt (0.93 mL, 5.34 mmol) was then added dropwise and the reaction was stirred at the same temperature for 1 h. The mixture was cooled to -78 °C before a solution of aldehyde 1012 (1.02 g, 4.95 mmol) in CH2Cl2 (15 mL) was added dropwise via cannula. Stirring was continued at -78 °C for 3 h before gradually warming to 0 °C. The reaction mixture was stirred for additional 3 h at 0 °C and then quenched by the addition of 0.1 M pH 7 phosphate buffer (7.5 mL) followed by MeOH (10 mL) at 0 °C. After stirring for 5 min, a solution of 30% aqueous H2O2 (7.5 mL) in Me-OH (15 mL) was added dropwise and stirred at the same temperature for 1 h before being concentrated under reduced pressure. The residue was diluted with Et2O, the phases were separated and the aqueous phase extracted with Et2O. The combined organic phase was washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure. Flash chromatography over silica gel (35% ethyl acetate in pet. ether) gave 11 (1.63 g, 83%) as a viscous, colorless oil. IR (CHCl3): v 3250, 2936, 1780, 1710, 1453, 1386, 1277, 1214, 1146, 763, 506 cm-1; 1H NMR (300 MHz, CDCl3): S 8.10-7.98 (m, 2H), 7.55 (t, J = 7.42 Hz, 1H), 7.43 (t, J = 7.5 Hz), 7.39-7.24 (m, 3H), 7.20 (d, J = 5.6 Hz, 2H), 4.71 (ddt, J = 10.4, 6.9, 3.3 Hz, 1H), 4.33 (t, J =6.5 Hz, 2H), 4.28-4.13 (m, 2H), 4.04-3.93 (m, 1H), 3.77 (qd, J = 7.0, 2.7 Hz, 1H), 3.25 (dd, J = 13.4, 3.2 Hz, 1H), 2.95 (s, 1H), 2.79 (dd, J = 13.4, 9.4 Hz, 1H), 1.87-1.42 (m, 6H), 1.27 (d, J = 7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3): S 178.0, 166.8, 153.3, 135.2, 133.1, 130.0, 129.0, 128.0, 127.3, 71.6, 66.2, 65.1, 55.1, 42.2, 38.2, 33.0, 28.5, 23.0, 10.4; HRMS (ESI): m/z calculated for C25H30O6N: [M+H]+ 440.2067, found 440.2044; [a]D25 = +29.0 (c 1.62, CDCl3). (5S,6fl)-7-((fl)-4-Benzyl-2-oxooxazolidin-3-yl)-5-(teri-butyldimethylsilyloxy)-6-methyl-7-oxoheptyl benzoate (12): To a stirred solution of 11 (1.60 g, 3.64 mmol) in DMF (15 mL) were added imidazole (800 mg, 12.3 mmol) and TBSCl (tert-butylchlorodimethylsilane) (950 mg, 7.4 mmol). After 18 h at 25 °C, the reaction mixture was added to 20% CH2Cl2: hexane (100 mL) and successively washed with 10% aq. NaHSO3 (25 mL) and water (2 x 25 mL). The organic layer was dried over Na2SO4 filtered, concentrated in vacuo and distilled to yield 12 (1.74 g, 87%) as a colorless oil. IR (CHCl3): v 3349, 3380, 3088, 2971, 2934, 1699, 1740, 1472, 1452, 1391, 1368, 1311, 1256, 1152, 992, 933, 771, 666, 560 cm-1; 1H NMR (300 MHz, CDCl3): S 8.10-7.98 (m, 2H), 7.55 (t, J = 7.4 Hz, 1H), 7.43 (t, J = 7.7 Hz, 2H), 7.28-7.38 ( m, 3H), 7.20 (d, J = 7.0 Hz, 2H), 4.6 (ddt, J = 10.2, 6.4, 3.1 Hz, 1H), 4.33 (t, J = 6.5 Hz, 2H), 4.12-4.27 (m, 2H), 4.02 (q, J = 5.4, 5.6 Hz, 1H), 3.88 (qd, J = 6.8, 1.6 Hz, 1H), 3.30 (dd, J = 13.2, 3.0 Hz, 1H), 2.78 (dd, J = 13.2, 9.6 Hz, 1H), 1.70 (m, 2H), 1.62-1.42 (m, 4H), 1.22 (d, J = 6.8 Hz, 3H), 0.90 (s, 9H), 0.20 (s, 6H); 13C NMR (75 MHz, CDCl3): S 175.2, 166.3, 153.0, 135.0, 133.1, 129.3, 129.1, 128.1, 127.6, 72.6, 65.7, 64.7, 56.3, 43.2, 35.0, 29.2, 26.3, 22.0, 19.0, 12.3, -4.5; HRMS (ESI): m/z calculated for C31H47O6N2Si: [M+Na]+ 571.3197, found 571.3174; [a]D : +10.53 (c 1.33, CDCl3). (5S,6S)-5-(ieri-Butyldimethylsilyloxy)-7-hydroxy-6- methylheptyl benzoate (13): To a stirred solution of 12 (1.70 g, 3.07 mmol) in THF (70 mL) at 0 °C was added a solution of NaBH4 (579 mg, 15.3 mmol) in pH 7 buffer (18.5 mL). The resulting solution was stirred for 10 min at 0 °C before being allowed to gradually warm to room temperature and continued stirring for overnight. The reaction was quenched by the addition of sat. aq. NH4Cl (20 mL) and stirred at room temperature for 1 h. The separated aqueous phase was extracted with EtOAc (2 x 25 mL). The combined organic phase was washed with brine, dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. Flash chromatography over silica gel (15% ethyl acetate in pet. ether) gave 13 (1.01 g, 87%) as a colorless oil. IR (CHCl3): v 3436, 2954, 2930, 2857, 1721, 1459, 1275, 1113, 1033, 836, 773, 712 cm-1; 1H NMR (300 MHz, CDCl3): S 8.02-8.10 (m, 2H), 7.55 (t, J = 7.3 Hz, 1H), 7.43 (t, /= 7.9 Hz, 2H), 4.70 (s, 1H), 4.33 (t, J = 6.7 Hz, 2H), 3.79-3.75 (m, 1H), 3.70 (t, J = 9.0 Hz, 2H), 3.56-3.48 (m, 1H), 1.97 ( m, 1H), 1.56-1.32 (m, 6H), 0.90 (s, 9H), 0.82 (d, J = 7.8 Hz, 3H), 0.20 (s ,6H); 13C NMR (75 MHz, CDCl3): S 166.7, 132.8, 130.1, 129.3, 128.4, 77.4, 65.5, 64.8, 39.4, 32.0, 28.7, 25.9, 22.7, 17.9, 12.1, -4.6; HRMS (ESI): m/z calculated for C21H37O4Si: [M+H]+ 381.24556, found 381.24414. (2_R,3S)-7-(Benzoyloxy)-3-(feri-butyldimethylsilyloxy)-2-methylheptanoic acid (7): To a stirred solution of 13 (1.0 g, 2.62 mmol) in CH2Cl2 (5 mL) at 0 °C were added Srinivas et al.: Stereoselective Synthesis of Southern Fragment 35G Acta Chim. Slov. 2016, 63, 344-35G BAIB (3 g, 9.31 mmol), catalytic amount of TEMPO in pH 7 buffer (3 mL). The resulting solution was stirred for 10 min at 0 °C before being allowed to gradually warm to room temperature with stirring for 1 h. The reaction was quenched by the addition of sat. aq. NH4Cl (20 mL) and stirred at room temperature for 1 h. The separated aqueous phase was extracted with EtOAc (2 x 25 mL). The combined organic phase was washed with brine, dried over anhydrous Na2SO4 filtered and concentrated under reduced pressure. Flash chromatography over silica gel (30% ethyl acetate in pet. ether) gave 7 (0.92 g, 89%) as a colorless oil. IR (CHCl3): v 2931, 2857, 1715, 1459, 1386, 1274, 1220, 1110, 1069, 1026, 936, 836, 773, 711, 675 cm1; 1H NMR (300 MHz, CDCl3): S 8.10-7.98 (m, 2H), 7.50 (t, J = 7.4 Hz, 1H), 7.43 (t, J= 7.5 Hz, 2H), 4. 33 (t, J = 6.7 Hz, 2H), 3.99 (q, J = 6.0, 5.2 Hz, 1H), 2.66-2.56 (m, 1H), 1.72-1.30 (m, 6H), 1.22 (d, J = 6.8 Hz, 3H), 0.90 (s, 9H), 0.20 (s, 6H); 13C NMR (75 MHz, CDCl3): S 165.6, 134.2, 130.0, 129.9, 128.4, 73.5, 65.3, 44.5, 33.5, 29.2, 26.2, 22.2, 18.4, 11.5, -5.4; HRMS (ESI): m/z calculated for C21H34O5Si: [M+H]+ 393.4556, found 392.4414. (2S,3S)-AUyl-2-(teri-butoxycarbonyl(methyl)ammo)-3- methylpentanoate (15): Na^O^i (2.55 g, 24.3 mmol) and Boc2O (3.94 g, 18.2 mmol) were added to a solution of L-isoleucine (3.5 g, 12.3 mmol), in H2O (20 mL) and THF (5 mL) at 0 °C. After the reaction mixture has been stirred at room temperature for 12 h, it was neutralized with HCl (10%) until pH 2 has been reached. The mixture was then extracted with EtOAc (3 x 50 mL), washed with brine, dried over Na2SO4. Concentration gave the crude N-Boc-isoleucine (2.6 g, 100%). NaH (60% in mineral oil, 2.45 g, 61.3 mmol) was added in portions to a solution of N-Boc-isoleucine (2.6 g, 9.09 mmol) and Mel (6.05 mL) in THF (50 mL) at 0 °C. After the reaction mixture has been stirred at room temperature for 36 h, it was poured into saturated NH4Cl solution (250 mL), extracted with EtOAc (3 x 150 mL) and dried over Na2SO4. Concentration gave N-methyl-N-Boc-isoleucine (2.53 g, 92%). K2CO3 (3.08 g, 22.3 mmol) and allyl bromide (1.4 mL, 16.9 mmol) were added to a solution of N-methyl-N-Boc-isoleucine (2.53 g, 10.9 mmol) in DMSO (40 mL). After the mixture has been stirred at room temperature for 12 h, it was portioned between EtOAc (75 mL) and brine (75 mL). The organic phase was separated and aqueous phase was extracted with EtOAc (2 x 100 mL). The combined organic phase was dried over Na2SO4 and concentrated. Flash chromatography gave 15 (2.5 g, 80.9%). IR (CHCl3): v 3089, 2971, 2936, 2880, 1741, 1701, 1650, 1480, 1456, 1393, 1367, 1313, 1255, 1183, 1145, 1047, 990, 931, 871, 773 cm-1; 1H NMR (300 MHz, CDCl3): S 5.97-5.84 (m, 1H), 5.34-5.20 (m, 1H), 4.62-4.60 (m, 2H), 4.55 (d, J = 11.1 Hz, 1H), 4.26* (d, J = 11.1 Hz, 1H), 2.81 (s, 3H), 2.78* (s, 3H), 2.04-1.95 (m, 1H), 1.45 (m, 10H), 1.13-1.01 (m, 1H), 0.92 (d, J = 6.0 Hz, 3H), 0.87 (d, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): S 172.3, 156.4, 132.1, 118.4, 80.3, 65.6, 63.8, 33.5, 30.8, 28.7, 24.5, 15.6, 10.4; HRMS (ESI): m/z calculated for C15H28O4N: [M+H]+ 286.20128, found 286.19969. [a]D25 = -74.7 (c 1.1, CHCl3). 'denotes the rotamer peaks. (2S,3S)-AUyl-2-((S)-2-(feri-butoxycarbonylammo)-N,3 -dimethylbutanamido)-3-methylpentanoate (8): A solution of (tert-butoxycarbonyl)-L-valine (0.35 g, 1.22 mmol), HATU (0.24 g, 1.8 mmol) and HOAt (0.34 g, 1.8 mmol) in CH2Cl2 (5 mL) was stirred at 0 °C under N2 atmosphere for 15 min, treated sequentially with salt [prepared from 15 (375 mg, 1.24 mmol) in dry CH2Cl2 (1 mL) at 0 °C on treatment with CF3COOH (0.1 mL)] and DIPEA (0.6 mL, 3.6 mmol) and stirred for 8 h. The reaction mixture was quenched with aq. satd. NH4Cl solution (10 mL). After 10 min, it was diluted with CHCl3 (2 x 10 mL) and washed with water (10 mL), NaHCO3 solution (10 mL) and brine (10 mL). The organic layers were dried over Na2SO4, evaporated and the residue was purified by column chromatography (60-120 mesh silica gel, 35% ethyl acetate in pet. ether) to afford 8 (509 mg, 84%) as a colorless syrup. IR (CHCl3): v 3333, 2966, 2945, 2862, 1742, 1706, 1658, 1462, 1367, 1294, 1178, 1001, 938, 876, 774 cm-1; 1H NMR (300 MHz, CDCl3): S 5.40-5.41 (m, 1H), 5.05 (d, J = 2.2 Hz, 2H), 4.40 (q, /= 2.6 Hz, 1H), 3.70 (s, 3H), 3.70-3.50 (m, 1H), 3.50-3.10 (m, 2H), 3.09 (s, 2H), 2.10-1.89 (m, 2H), 1.50 (s, 9H), 1.32-1.10 (m, 5H), 1.00-0.80 (m, 8H); 13C NMR (75 MHz, CDCl3): S 173.5, 171.4, 156.4, 118.6, 79.8, 60.4, 55.3, 52.2, 33.4, 31.4, 29.8, 24.5, 19.8, 16.4, 11.2; HRMS (ESI): m/z calculated for C20H36N2O5Na: [M+Na]+ 407.2562, found 407.2414. 20 36 2 5 (5S,6R,9R,12S)-Allyl-5-(4-(benzoyloxy)butyl)-12-sec-butyl-9-isopropyl-2,2,3,3,6,11-hexamethyl-7,10-dioxo-4-oxa-8,11-diaza-3-silatridecan-13-oate (16): A solution of acid 7 (510 mg, 1.29 mmol), HATU (240 mg, 1.8 mmol) and HOAt (340 mg, 1.8 mmol) in CH2Cl2 (5 mL) was stirred at 0 °C under N2 atmosphere for 15 min, treated sequentially with TFA salt [prepared from 8 (450 mg, 1.2 mmol) in dry CH2Cl2 (1 mL) at 0 °C on treatment with CF3COOH (0.1 mL)] and DIPEA (0.6 mL, 3.6 mmol) and stirred for 8 h. The reaction mixture was quenched with aq. satd. NH4Cl solution (10 mL). After 10 min, it was diluted with CHCl3 (2 x 10 mL) and washed with water (10 mL), NaHCO3 solution (10 mL) and brine (10 mL). The organic layers were dried over Na2SO4, evaporated and the residue purified by column chromatography (60-120 mesh silica gel, 45% ethyl acetate in pet. ether) to afford 16 (725 mg, 85%) as a colorless syrup. IR (CHCl3): v 3347, 3233, 2966, 2926, 2915, 2854, 2840, 1739, 1701, 1667, 1651, 1460, 1448, 1380, 1220, 1172, 1110, 1069, 1026, 1003, 936, 836, 773, 771, 711, 676, 667 cm-1; 1H NMR (300 MHz, CDCl3): S 8.00 (d, J = 7.5 Hz, 2H ), 7.55 (d, J = 8.3 Hz, 1H), 7.433 (t, J = 7.5 Hz, 2H ), 5.96-5.79 (m, 1H), 5.39-5.18 (m, 2H), 5.11-5.01 (m, 1H), Srinivas et al.: Stereoselective Synthesis of Southern Fragment Acta Chim. Slov. 2016, 63, 344-350 349 4.65-4.54 (m, 2H), 4.34-7.27 (m, 3H), 3.82-3.68 (m, 3H), 3.10-3.05 (m, 2H), 2.06-1.89 (m, 2H), 1.83-1.50 (m, 3H), 1.45-1.37 (m, 3H), 1.36-1.19 (m, 4H), 1.20-1.05 (m, 1H), 1.01-0.78 (m, 22H), 0.10-0.03 (m, 6H); 13C NMR (75 MHz, CDCl3): S 174.1, 171.2, 168.4, 133.5, 132.5, 130.5, 129.2, 74.5, 66.0, 65.3, 60.1, 58.2, 54.1, 49.2, 34.2, 32.1, 30.1, 29.4, 26.2, 25.1, 19.2, 16.4, 14.4, 11.2, -5.4. HRMS (ESI): m/z calculated for C36H60N2O7SiNa: [M+Na]+ 683.4556, found 683.4214. (5S,6fl,9S,12S)-AUyM2-((S)-sec-butyl)-5-(4-hydroxy-butyl)-9-isopropyl-2,2,3,3,6,11-hexamethyl-7,10-dio-xo-4-oxa-8,11-diaza-3-silatridecan-13-oate (6): To a stirred solution of 16 (700 mg, 1.06 mmol) in MeOH (5 mL) was added K2CO3 (45 mg, 0.33 mmol). The reaction was stirred at room temperature until complete by TLC (2 h). The mixture was then diluted with CH2Cl2 (25 mL) and washed with H2O (5mL). The separated aqueous phase was extracted with CH2Cl2 (3 x 10 mL) and the combined organic phase dried over Na2SO4, filtered, evaporated and the residue was purified by column chromatography (60-120 mesh silica gel, 52% ethyl acetate in pet. ether) to afford 6 (440 mg, 75%) as a colorless syrup. IR (CHCl3): v 3347, 3300, 3233, 2956, 2926, 2925, 2854, 2840, 1701, 1667, 1651, 1460, 1448, 1380, 1220, 1172, 1110, 1069, 1026, 1003, 936, 836, 773, 771, 711, 676, 667 cm-1; 1H NMR (300 MHz, CDCl3): S 5.96-5.79 (m, 1H), 5.39-5.18 (m, 2H), 5.11-5.01 (m, 1H), 4.65-4.54 (m, 2H), 4.50 (brs, 1H), 4.34-4.27 (m, 3H), 4.25-4.15 (m, 2H), 3.68 (m, 3H), 3.10-3.05 (m, 2H), 2.06-1.89 (m, 2H), 1.83-1.50 ( m, 3H), 1.45-1.37 (m, 3H), 1.36-1.19 (m, 4H), 1.20-1.05 (m, 1H), 1.01-0.78 (m, 19H), 0.10-0.03 (m, 6H); 13C NMR (75 MHz, CDCl3): S 174.1, 171.2, 132.5, 74.5, 66.0, 65.3, 62.8, 60.1, 58.2, 54.1, 49.2, 34.2, 32.1, 30.1, 29.4, 26.2, 25.1, 19.2, 16.4, 14.4, 11.2, -5.4; HRMS (ESI): m/z calculated for C29H56N2O6SiNa: [M+Na]+ 579.3914, found 579.3812. nic phase dried over Na2SO4, filtered and evaporated and the residue was purified by column chromatography (60-120 mesh silica gel, 5% ethyl acetate in pet. ether) to afford 5 (352 mg, 92%) as a yellow syrup. 1H NMR(300 MHz, CDCl3): S 5.86-5.74 (m, 1H), 5.29-5.08 (m, 2H), 5.04-5.01 (m, 1H), 4.45-4.34 (m, 2H), 4.14-4.07 (m, 3H), 4.02-3.95 (m, 2H), 3.58 (m, 3H), 3.10-3.05 (m, 2H), 2.20 (s, 1H), 2.06-1.89 (m, 2H), 1.83-1.50 ( m, 3H), 1.45-1.37 (m, 3H), 1.36-1.19 (m, 4H), 1.20-1.05 (m, 1H), 1.01-0.78 (m, 19H), 0.10-0.03 (m, 6H); 13C NMR (75 MHz, CDCl3): S 172.1, 170.2, 129.5, 83.9, 71.5, 68.2, 61.3, 60.8, 60.1, 53.2, 52.1, 48.2, 33.2, 32.1, 30.1, 29.4, 26.2, 25.1, 18.7, 16.4, 14.4, 11.2, -5.4; HRMS (ESI): m/z calculated for C30H54N2O5SiNa: [M+H]+ 551.3140, found 579.3120. 4. Conclusions In conclusion, a practical and stereoselective synthesis of C21-C41 fragment of hantupeptin A having five stereo centers, two amide linkages and one ester linkage was demonstrated with differential protective groups to allow further extensions. The key features of the strategy are the successful utilization of Evan's Aldol reaction, TEMPO mediated oxidation and Ohira-Bestmann homologation. Furthur investigation towards the total synthesis of hantupeptin A are in progress. 5. Acknowledgements A. Srinivas is thankful to CSIR, New Delhi for Research Associate fellowship, Director, Indian Institute of Chemical Technology (IICT), Hyderabad for the providing research facilities and Dr. G. V. M. Sharma, Chief Scientist, IICT, Hyderabad for valuable guidance. (5S,6fl,9S,12S)-Allyl 12-((S)-sec-butyl)-9-isopropyl-2,2,3,3,6,11-hexamethyl-7,10-dioxo-5-(pent-4-ynyl)-4-oxa-8, 11-diaza-3-silatridecan-13-oate (5): To a stirred solution of 6 (420 mg, 0.755 mmol) and powdered 4 A molecular sieves (650 mg) in CH2Cl2 (15 mL) were subsequently added 4-methylmorpholine-N-oxide (227 mg, 1.94 mmol) and tetrapropylammonium perruthenate (22.9 mg, 0.065 mmol) and the mixture was stirred at room temperature for 2 h. The reaction mixture was filtered through a pad of silica gel and the filtrate was concentrated under reduced pressure to give the aldehyde as a colorless oil. The residue was placed under high vaccum for 2 h before being used in the subsequent reaction without puri-fiation. The aldehyde, K2CO3 and the Ohira-Bestmen reagent (262 mg, 1.32 mmol) were stirred for 16 h. The mixture was then diluted with CH2Cl2 (25 mL) and washed with H2O (5 mL). The separated aqueous phase was extracted with CH2Cl2 (3 x 10 mL) and the combined orga- 6. References 1. A. Yurek-George, A. R. Cecil, A. H. Mo, S. Wen, H. Rogers, F. Habens, S. Maeda, M. Yoshida, G. Packham, A. Ganesan, J. Med. Chem. 2007, 50, 5720-5726. http://dx.doi.org/10.1021/jm0703800 2. J. Adrio, C. Cuevas, I. Manzanares, M. M. Joullie, J. Org. Chem. 2007, 72, 5129-5138. http://dx.doi.org/10.1021/jo070412r 3. B. Liang, D. J. Richard, P. S. Portonovo, M. M. Joullie, J. Am. Chem. Soc. 2001, 123, 4469-4474. http://dx.doi.org/10.1021/ja010222c 4.P. S. Pan, K. L. McGuire, S. R. McAlpine, Bioorg. Med. Chem. Lett. 2007, 17, 5072-5077. http://dx.doi.org/10.1016/j.bmcl.2007.07.025 5. K. Otrubova, G. Lushington, D. V. Velde, K. L. McGuire, S. R. McAlpine, J. Med. Chem. 2008, 51, 530-544. Srinivas et al.: Stereoselective Synthesis of Southern Fragment 35G Acta Chim. Slov. 2016, 63, 344-35G http://dx.doi.org/1G.1G21/jmG7G731a 6. R. Lemmens-Gruber, M. R. Kamyar, R. Dornetshuber, Curr. Med. Chem. 2009, 16, 1122-1137. http://dx.doi.org/1G.2174/G929867G9787581761 7. F. Sarabia, S. Chammaa, A. S. Ruiz, L. M. Ortiz, F. J. Herrera, Curr. Med. Chem. 2004, 11, 13G9-1332. http://dx.doi.org/1G.2174/G929867G43365224 8. M. D. Vera, M. M. Joullie, Med. Res. Rev. 2002, 22, 1G2-145. http://dx.doi.org/1G.1GG2/med.1GGG3 9. A. Tripathi, J. Puddick, M. R. Prinsep, P. P. F. Lee, L. T. Tan, J. Nat. Prod. 2009, 72, 29-32. http://dx.doi.org/1G.1G21/np8GG448t 1G. A. Tripathi, J. Puddick, M. R. Prinsep, P. P. F. Lee, L. T. Tan, Phytochemistry 2010, 71, 3G7-311. http://dx.doi.org/1G.1G16/j.phytochem.2GG9.1G.GG6 11. D. K. Gupta, G. C. Ding, Y. C. Teo, L. T. Tan, Nat. Prod. Commun. 2016, 11, 69-72. 12. (a) A. Srinivas, A. Nagaraj, C. S. Reddy, Eur. J. Med. Chem. 2010, 45, 2353-2358. http://dx.doi.org/1G.1G16/j.ejmech.2G1G.G2.G14 (b) C. S. Reddy, A. Srinivas, M. Sunitha, A. Nagaraj, Hete- rocycl. Chem. 2010, 47, 13G3-13G. http://dx.doi.org/10.1002/jhet.474 (c) C. S. Reddy, A. Nagaraj, A. Srinivas, G. P. Reddy, Indian J. Chem. 2010, 49B, 617-622. (d) A. Srinivas, C. S. Reddy, A. Nagaraj, Chem. Pharm. Bull. 2009, 57, 685-693. http://dx.doi.org/10.1248/cpb.57.685 (e) C. S. Reddy, A. Srinivas, A. Nagaraj, J. Heterocyclic. Chem. 2009, 46, 497-502 f) C. S. Reddy, A. Nagaraj, A. Srinivas, G. P. Reddy, Indian J. Chem. 2009, 48B, 248-254. (g) C. S. Reddy, A. Srinivas, A. Nagaraj, J. Heterocyclic. Chem. 2008, 45, 999-1003. (h) C. S. Reddy, A. Srinivas, A. Nagaraj, J. Heterocyclic. Chem. 2008, 45, 1121-1125. (i) C. S. Reddy, G. P. Reddy, A. Nagaraj, A. Srinivas, Org. Commun. 2008, 1, 84-94. (j) C.S Reddy, A. Srinivas, A. Nagaraj, Indian J. Chem. 2008, 47B, 787-791. 13. K. Kubota, E. Yamamoto, H. Ito, J. Am. Chem. Soc. 2015, 137, 420-424. http://dx.doi.org/10.1021/ja511247z 14. A. D. Fotiadou, A. L. Zografos, Org. Lett. 2011, 13, 45924595. http://dx.doi.org/10.1021/ol2017802 15. J. R. Gage, D. A. Evans, Org. Synth. 1990, 68, 83-91. http://dx.doi.org/10.15227/orgsyn.068.0083 Povzetek Opisana je stereoselektivna sinteza južnega fragmenta (C21-C41) hantupeptina A. Zahtevana stereokemija P-hidroksi-a-metil kislinske enote je bile dosežen z aldolno reakcijo z uporabo Evansovega kiralnega pomagala, ki ji je sledila uvedba terminalnega alkinskega ostanka s pomočjo Ohira-Bestmannovega reagenta. Srinivas et al.: Stereoselective Synthesis of Southern Fragment DOI: 10.17344/acsi.2016.2335 Acta Chim. Slov. 2016, 63, 351-362 351 Scientific paper Experimental and Computational Study of the Thermodynamic Properties of Trivalent Cobalt Schiff Base Complexes with Cyclic Amines Sheida Esmaielzadeh,* Leila Azimian and Zohreh Zare Department of Chemistry, Darab branch, Islamic Azad University, Darab, I. R. Iran * Corresponding author: E-mail: esmaielzadehsheida@yahoo.com Received: 11-02-2016 Abstract Some cobalt(III) complexes with a potentially tetradentate unsymmetrical NNOS Schiff base ligand have been synthesized and characterized using IR, 'HNMR, UV-Vis spectroscopy and elemental analysis. The equilibrium constants were measured spectrophotometrically for 1:1 adduct formation of the cobalt(III) complexes with some cyclic amines in acetonitrile as solvent at constant ionic strength (I = 0.1 M NaClO4), and at various temperatures. In addition, the ground state geometries of the complexes were optimized using density functional theory (DFT) at B3LYP/6-311G** level. Binding energy, thermodynamic parameters, structural parameters and electronic structures of complexes are investigated. The theoretical investigations were done for comparing with the experimental results. Our comparison between the computational and experimental results revealed that the cobalt(III) complexation process is spontaneous, exothermic and entropically unfavorable. Keywords: Cobalt complexes; Unsymmetrical Schiff base; Thermodynamic parameters; computational methods; experimental data. 1. Introduction Synthetic oxygen carriers are of great interest as models to mimic oxygen caring metalloenzymes1 and oxygenases, such as hemoglobin and cytochrome P-450,2 which play important roles in the catalytic oxygenation mechanism of organic substrates.3 The Schiff base ligands and their complexes represent one of the most widely utilized classes of ligand in synthetic oxygen carrier compound. This usually arises from their structural similarity to those found in biological systems.4 The Co(III) Schiff base complexes have been extensively used to mimic cobalamin (B12) coenzymes,5 dioxygen carriers and oxygen activators and for enantioselective reduc-tion.6 These complexes are an important class of coordination compounds not only because being interesting B12 models but also due to their interesting magnetic properties, spectroscopic characteristics and catalytic aspects.7 Co(III) complexes with the tetradentate Schiff base ligands have shown specific hypoxic radiosensitization and thermosensi-tization as well as antitumor activity in vivo.8 These cobalt complexes with two amines in axial positions have also been used as antimicrobial and antiviral agents.9 Many studies have been focused on the thermodynamic, kinetic, theoretical and catalytic aspects of this class of compounds.10,11 The thermodynamics and kinetics of complex formation, stability and mechanistic behavior of five-coordinate square-pyramidal or trigonal bipyramidal complexes of first-row transition metals have received significantly less attention although such five-coordinate complexes can exhibit significantly different ligand substitution behavior since they are, in principle, able to coordinate an additional nucleophile in the transition state. In contrast six-coordinate complexes undergo dissociative li-gand substitution reaction. Thus, the study of their behavior is of fundamental importance to the understanding of complex formation and ligand substitution reaction in general. Base on this experience and in order to contribute to a better understanding of the properties of five and six coordinated cobalt(III) Schiff base complexes, we report here the synthesis and characterization of some novel apparently five-coordinated complexes with apical tertiary phosphines as complex [Co(Chel)(PBu3)]+ where Chel: methyl-2-{N-[2-(acetone)ethylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate, (cdacacen), methyl-2- Esmaielzadeh et al.: Experimental and Computational Study 352 Acta Chim. Slov. 2016, 63, 351-362 {N- [2-(acetone)phenylidynenitrilo] ethyl} amino-1-cyclo-pentenedithiocarboxylate, (cdacPhen), methyl-2-{N-[2-(acetone)triflourolidynenitrilo]ethyl}amino-1-cyclopen-tenedithiocarboxylate, (cdacCF3en). The thermodynamic parameters of five-coordinated complexes with cyclic amine groups at constant ionic strength and at various temperatures with the goal of evaluation of solvent effect and of the effect of equatorial li-gand on electronic and steric properties have been studied. Also, we describe the results of theoretical calculations on the title compounds. The optimized structure, molecular orbital diagram and relative energies of cobalt(III) complexes have been calculated with density functional theory (DFT). A comparison between the calculated results (structure, formation constant, thermodynamic parameter) and experimental results are used to validate the conclusions. 2. Experimental 2. 1. Chemicals and Instruments Benzoylacetone, acetylacetone, 1,1,1-trifluoroace-tone, 1,2-ethelendiamine, ammonia solution, carbon disulfide, dimethylsulfate, cyclopentanone, methanol, etha-nol, acetonitrile, chloroform, hydrochloric acid, cobalt acetate tetrahydrate, tributylphoshine, imidazole, 2-methyl imidazole, 2-ethyl imidazole, benzimidazole, sodium perchlorate monohydrate were purchased from Merck and Fluka. All chemicals and solvents were of analytical reagent grade and were used without any further purification. The solvents used for thermodynamic measurements were dried over molecular sieves (3 A). The Schiff base ligands (H2cdacacen, H2cdacPhen, H2cdacCF3en) were prepared by following published procedures.19 Elemental analyses were performed on Termo Fi-ninngan-Flash 1200 analyzer. The 1H NMR spectra were obtained on a Bruker Avance DPX 400 MHz spectrometer in DMSO-d6 using TMS as an internal standard. Electronic spectra were recorded on a Perkin Elmer (LAMBDA 2) UV-Vis spectrophotometer with an appropriate quartz cell for complex solution. The temperature was controlled by electronic thermostate through the compartment surrounding the cell. The IR spectra of the compounds were carried out as KBr discs on a Shimadzu FTIR 8300 infrared spectrophotometer. The molar conductance ca. 10-3 M solutions of the complexes in DMF were measured by means of a Jenway 4310 conductivity meter and a diptype cell with a platinized electrode. 2. 2. Synthesis of Ligands and Cobalt(III) Complexes The Schiff base ligands were prepared according to the literature by condensation of the half units methyl-2- (N-2'-aminoethane)amino-1-cyclopentenedithiocarboxy-late (Hcden) with acetylacetone, benzoylacetone and 1,1,1-trifluoro-2,4-pentanedione in methanol at room temperature and were purified from methanol/chloroform 2:1 (V:V).12 The novel [Co(cdacacen)(PBu3)]ClO4 ■ H2O, [Co(cdacPhen)(PBu3)]ClO4 ■ H2O and [Co(cdacCF3en) (PBu3)]ClO4 ■ H2O were synthesized as follow: To a reflu-xing solution of the unsymmetrical ligands (H2cdacacen, H2cdacPhen, H2cdacCF3en) (0.1 mmol) in 10 mL of chloroform/methanol mixture (2:1) under N2 atmosphere, was added a solution of Co(CH3COO)2 ■ 4H2O (1 mmol) in methanol (10 mL) dropwisely. The deep brown or red solution of Co(II)(L) complexes were precipitated, then the tributylphosphine (0.1 mmol) was added and the reaction mixture was refluxed for 5-6 hours. The formed Co(II) complex was oxidized by blowing air into the solution for 2 hours, and the solution was filtered. An appropriate amount of sodium perchlorate (0.1 mmol) was added to the filtrate. The resulting green crystals were formed after staying for 48 h. They are collected by filtration and washed with portions of distilled water and methanol. The resulting green crystals were purified by recrystallization in 50:50(V/V) methanol/ water, and were finally dried in vacuum at 30 °C for 24 h. Caution: Although no difficulties were experiences, cobalt(III) complexes were isolated as their perchlorates, and therefore, they should be handled as potentially explosive compounds. 2. 3. Thermodynamic Studies The adduct complexes were obtained from the reaction of the acceptors with the donors, according to equation (1) [Co(Chel)(PBu3)]+ + Amine o [Co(Chel)(PBu3)(amine)]+ (1) where Chel = cdacacen, cdacPhen, cdacCF3en, and Amine = Im, 2-MeIm, 2-EtIm, BzIm. The formation constant measurements were performed by spectrophotometric titration at 283, 293, 303 and 313 K. In a typical titration, 2.5 mL of solution (from each complex (10-5-10-4 M) with a constant ionic strength (I = 0.1 M; by adding sodium perchlorate in CH3CN) was titrated with the amine solution in the same solvent. The titration was carried out by adding aliquots of the amine with a Hamilton microlitre syringe. The donor concentrations varied in the range of 1-10 folds in excess, which was low enough to avoid substitution of PBu3 by amine. The absorption measurements were carried out at various wavelengths in 660-760 nm where the difference in absorption was the maximum after the equilibrium was assessed, since this is the optimal range for detecting the difference between the product and the substrate, while the donors show no absorption at those wavelengths. As Esmaielzadeh et al.: Experimental and Computational Study ... Acta Chim. Slov. 2016, 63, 351-362 353 330 460 560 660 750 860 Wavelength (nm) Figure 1. The spectral titration curve of [Co(cdacacen)(PBu3)]+ with Im in CH3CN (I = 0.1 M ClO4, T = 293K). an example, the variation of the electronic spectra for [Co(cdacacen)(PBu3)]ClO4 H2O titrated with Im at 293 K in CH3CN is shown in Figure 1. The isosbestic points for this system show that there is only one reaction in equilibrium. The same are valid for the other systems. 2. 4. Computational Details The fully gas geometry optimization and the relative stability and molecular properties of the structures under investigation were carried out at density functional theory level13 using gradient technique14 and 6-311G** basis set.15 The DFT calculations were carried out with the B3LYP functional, in which Becke's nonlocal exchange16 and the Lee-Yang-Parr correlation functional17 were applied. After the completion of the optimization the Hessian (second derivatives of the energy as a function of the nuclear coordinates) was calculated and checked for positive definiteness to assess whether the structures are true minima.13,18 The harmonic vibrational frequencies were then derived from the numerical values of these second derivatives and used to obtain the thermodynamic properties Gibbs free energy contributions at 283 K. All the computation in the present study was performed using Gaussian03 for windows program.19 3. Results and Discussion 3. 1. Spectral Studies 3. 1. 1. The Elemental Analyses and Molar Conductivity The cobalt(III) complexes were characterized by elemental analysis and molar conductivity (Table 1). The results of CHNS analysis are in good agreement with theoretical values. The analytical data show that the metal to ligand ratio is 1:1 in all complexes. This is supported by molar conductivity measurements of the complexes. All of the complexes are stable at room temperature in air and are insoluble in water and nonpolar solvents. However, they are soluble in an acetonitrile, methanol, ethanol, DMF and DMSO completely. The solution conductivity measurements were performed to establish the electrolyte type of the complexes. The molar conductivity at 10-3 M for the complexes in DMF are in the range expected for their formulation as 1:1 electrolytes20 as shown in Table 1. 3. 1. 2. 1H NMR Spectra To further confirm the bonding pattern in these complexes, 1H NMR spectra of the cobalt(III) complexes were recorded in DMSO-d6 using TMS as an internal standard and show that the cobalt in these complexes is low spin, the data was collected in Table 1. The 1H NMR spectra of the ligands show OH and NH protons signal at 5 12.39-12.45 and 10.93-11.57 ppm. Disappearance of these signals due to -OH and -NH protons in the spectra of the cobalt(III) complexes indicates the deprotonation of these groups which supports the coordination of ligand through oxygen and nitrogen atoms with cobalt atom.21 A singlet peak at 2.19-2.36 ppm with three proton integration has been assigned to the methyl group of the acetyl moiety. The proton chemical shifts for the coordinated PBu3 appear at 0.71-2.06 ppm and are in agreement with the previous results observed for metal complexes of phosphine as axial ligand.22 3. 1. 3. Mode of Bonding and IR Spectra The IR spectra of the complexes were compared with those of the free ligands in order to determine the coordination sites that may be involved chelation. The broad bands in the range of 2947-3338 cm-1 is assigned to the stretching frequencies of the v(OH) of the water molecules associated to the complexes.23 The weak bands at 2939-2966 cm-1 in the ligands are attributed to the stretching vibration of CH modes. In cobalt complexes containing PBu3 these bands were very strong, assignable to C-H vibrations of PBu3.12 The v(C=N) stretching vibration was found at 1600-1640 cm-1 in the free ligand12 and this band was shifted to lower wave numbers in the complexes, indicating the participation of the azomethine nitrogen in thecoordination.24 The medium sharp bands corresponding to v(C-O) stretching vibration appeared at 1281 cm-1 and are shifted by about 25-30 cm-1 to lower energy region in the cobalt complexes compared to that of the free ligands. This phenomenon appears to be due to the coordination of oxygen (CO group) to the cobalt ion.25 The very strong, sharp and single bands at 1091-1093 cm-1 gives evidence for the presence of ionic perchlorate in all the complexes.26 Also, Esmaielzadeh et al.: Experimental and Computational Study ... 354 Acta Chim. Slov. 2016, 63, 351-362 coordination of Shiff base ligand to the cobalt ion through the sulfur atom is expected to reduce electron density in the thiol bond and lower the v(C-S) absorption frequency in complexes.27 New bands in the range of 570-581 cm-1 and 427-436 cm-1 which are not present in the free Schiff base are due to v(M-O) and v(M-N) vibrations,25 and the appearance of these vibrations support the involvement of the nitrogen and oxygen atoms of the azomethine and C-O groups in the complexation with the cobalt ion under investigations. 3. 1. 4. Electronic Absorption The UV-Vis spectrum of Schiff base ligands in CH3CN consists of a relatively intense band centered at 337 nm assigned to n ^ n* transition and a second band at 362-365 nm corresponding to n ^n* transition excitation.12 After complexation with Co(III) the band at 362-365 nm did not change appreciably in all the reactions studied. Moreover, an intense d ^ n* charge transfer band appears in the 670-700 nm region in the spectra of the five-coordinated complexes studied (Table 1). The d ^ n* absorption band vanished to the adduct formation and the six-coordinated product species show a new absorption band at 450-470 nm region that is a shoulder28 (See Figure 1). 3. 2. Thermodynamic Parameters and the Formation Constant 3. 2. 1. Thermodynamic Interpretations The formation constants of the various cobalt(III) unsymmetrical Schiff base complexes were calculated by Ketelaar's equation (2).29 (2) where CA and CD are the initial concentrations (mol L-1) of the acceptor and the donor, respectively. A is the optical density of the solution including the acceptor, the donor and the adduct complex, Aa and AD are the optical densities of the pure acceptor and the pure donor in the solution of concentrations AA and CD; eC, eA and eD are the molar extinction coefficients (mol-1 L cm-1) of the complex, the acceptor and the donor, respectively. K is the formation constant of the formed complex and the cell optical path length is 1 cm. The linear plots of P = CA x CD / (A - AA - AD ) vs. C = CA + CD) should produce a straight line if only a 1:1 complex is formed; while a mixture of 1:1 and 1:2 or only o U o sc" tt o 3 o I——I CN O K s • « Oh ù* r Ü OO c5 o H ^ /-y & o o G o a T3 u cn cn "S ^ ^o a\ r r'O j U r- o si tt o Ü o w cj CÛ fe 'S Ja 2 — u O IN ■S z o 'Or^ u^ o si tt 2 o R se" s eu ? o > . o NO o o > « CO CO M ag iS > ^ o\ r-co o "n œ ci ÎV îi, g S il V O CO ( & m >n 3T - ^ u u o > « NO o CO CO M 9 0 o (M tZ 1 u "I S CO O as as o in o V CO U CO u > o as > « t- ^ (N CO ■^t M O1^ O CO ^ co-^t nooi> hOTl CO \o w f~ CO ^ O ^ c? aT S u l1 (M « OO S^SC » 00^ i-U NO (N O - g U 9 -H U r- V ci eu OO ^ m NO (J ôse U -.t I OO eu ^^ OC I ö eu 2 ur s se lu s - m OO » pr se Sî î^ E Sj se «r ^^ Esmaielzadeh et al.: Experimental and Computational Study ... Acta Chim. Slov. 2016, 63, 351-362 355 Figure 2. The Ketelaar plots of variable P vs. C for [Co(cdaca-cen)(PBu3)]+ with Im at different temperatures (°C) in CH3CN, where, P = CA X C^, / (A - AA - A°, ) and C = CA + Q. 1:2 complexes in a system would lead to a curve. The formation constants of the studied cobalt(III) Schiff base complexes were calculated from the ratio of the slope to the intercept. The linear plot of P vs. C for [Co(cdaca-cen)(PBu3)]ClO4.H2O titrated with Im at 283-313 K in CH3CN is shown in Figure 2 which signify that only a 1:1 adduct is formed. Similar plots are obtained for the other systems. The thermodynamic parameters of the studied co-balt(III) unsymmetrical Schiff base complexes were calculated by using of the well-known van't Hoff equation (3): lnK = -AH°/RT + AS°/R (3) where K is the formation constant, R is the gas constant and T is the temperature. Thermodynamic parameters of the studied complexes were obtained from the linear plots of lnK vs. 1/T. The linear plots for [Co(cdacacen)(PBu3)]ClO4 ■ H2O with Im are shown in Figure 3. The similar plots are obtained for other systems. The values of AH0 and AS0 were obtained from the slope and the intercept, respectively. The AG° of adduct formation was obtained according to equation (4) (Table 3). AG° = AH° - TAS° (4) 3. 2. 2. The Equatorial Schiff Base Ligands on the Acceptor Property of Cobalt(III) Complexes Effect It is assumed that when cobalt ion is chelated in a macrocycle having delocalized electronic structure, the complex loses its transition character and might be kineti-cally labile. The extent to which this happens is likely to be strongly dependent on the structure of the Schiff base chelating system acting as acceptor of the donated charge. The equatorial ligands play important role in stability and reactivity of their complexes. This reactivity is affected by the steric and the electronic effects of the Schiff base ligands. For investigation of these properties of Schiff bases on the acceptor properties of cobalt(III) complexes, the thermodynamic study of these complexes with amines as donors in CH3CN were carried out. On the bases of the results (Table 2) the formation of adducts follow the sequence below: [Co(cdacacen)(PBu3)]+ > [Co(cdacPhen)(PBu3)]+ > [Co(cdacCF3en)(PBu3)]+ The electron n-acceptor qualities or donor ability of the substituents group on the ketones moiety on the Schiff base can influence the ability of the acceptor properties of the complexes. The cdacCF3en ligand is stronger acceptor than cdacacen and cdacPhen, and the presence of phenyl withdrawing group causes the cdacPhen being a weaker Schiff base than cdacacen. So, the cobalt ion in [Co(cdac-CF3en)(PBu3)]+ has more acceptor properties than the cobalt ion in other complexes. Accordingly, [Co(cdac-CF3en)(PBu3)]+ forms more stable adduct with the water or solvent molecule (equation 5), in the six-coordinated complex a water or a polar solvent molecule occupies the sixth position, the interaction with the incoming donor is very weak30 and the reaction is shifted to the right by decreasing the electron donating power of Schiff base. Therefore, their tendency for the reaction with amines (as a donor) decrease, hence their formation constants with donors are lower.31 [Co(Chel)(PBu3)]+ + S o [Co(Chel)(PBu3)S]+ (5) where S = HO or solvent molecule. Figure 3. The plots of lnK vs. 1/T for [Co(cdacacen)(PBu3)]+ with Im in CHCN. 3. 2. 3. The cyclic Amine Donor Effect In this part of the report, four donors Im, 2-MeIm, 2-EtIm and BzIm have been examined as donors. We tried to investigate the steric and the electronic effects of these bases on their interaction with the newly synthesized complexes. The electron donating groups in the base increase the tendency of the organic bases toward the small acids like H+. On the other hand, the binding tendency of the organic bases toward the cobalt(III) centre is almost compatible with their steric rather than their basi- Esmaielzadeh et al.: Experimental and Computational Study ... 356 Acta Chim. Slov. 2016, 63, 351-362 city character when the size of acids were increased.32 Although the basic constants, Kb, of the donor amines applied in this study are increased according to the trend: Im, 2-MeIm, 2-EtIm, BzIm have the pKa = 6.73, 7.52, 7.86, 5.12,33 the formation constants for these bases with [Co(cdacacen)(PBu3)]+, [Co(cdacPhen)(PBu3)(PBu3)]+ and [Co(cdacCF3en)(PBu3)]+ complexes were increased according to the following trend: Im > 2-MeIm > 2-EtIm > BzIm. This trend shows that the steric factor is more important than electronic factor for each donor toward a given acceptor. When the steric hindrance of the entering li-gand is increased, the formation constant is lower for all systems (See Table 2). 3. 2. 4. The Solvent Effect on Formation Constant To study the effects of the solvent on the equilibrium of five- and six-coordinated Schiff base cobalt complexes we determined the formation constants of [Co(cdacacen)(PBu3)]+ with Im in four solvents i.e. ace-tonitrile, THF, DMF and ethanol. The formation constant in solvent are dependent on many factors, one of them is Gutmann donor number.34 The Gutmann donor number for solvents is shown in Table 3. It seems that the formation constants are decreased with increasing donor number of solvents (see Table 3). These results show that the five-coordinated complexes were found to be more stable in a solvent with higher donor number. In other words, a solvent with higher donor number can coordinate to a five-coordinated complex and stabilizes it toward a higher coordination number. Therefore, the trend of the influence of the solvent on the reactivity of the studied complex toward a given Im donor is: CH3CN > THF > DMF > EtOH. 3. 2. 5. The Temperature Effect on Cobalt(III) Complex Formation The thermodynamic parameter such as AH° and AS° are dependent to temperature indirectly. In this work, equilibrium constants were carried out at various temperatures. Because of bond formation, by increasing the temperature, the formation constants were decreased. In general, the AH° value and its sign, is dependent on two factors: The solvation effect and the heat of ad-duct formation.35 According to the results (Table 4) the Table 2. The formation constants, (10 2 X Kf (M ')), for Co(III) Schiff base complexes with various cyclic amines in CH3CN at different temperature (K). Co(III) complexes 283 293 303 313 [Co(cdacCF3en)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm 20.0 ± 0.4 17.2 ± 0.3 15.1 ± 0.2 8.5 ± 1.4 18.7 ± 0.8 16.4 ± 0.2 12.7 ± 0.1 5.2 ± 0.2 15.3 ± 1.2 14.8 ± 0.4 10.2 ± 0.7 3.6 ± 0.3 12.1 ± 0.3 11.2 ± 0.8 7.7 ± 0.4 2.3 ± 0.2 [Co(cdacPhen)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm 25.7 ± 0.9 21.8 ± 0.2 17.2 ± 1.3 12.7 ± 0.4 20.7 ± 1.1 18.5 ± 0.7 15.6 ± 0.8 10.1 ± 0.6 17.4 ± 0.3 16.3 ± 0.9 13.8 ± 0.4 7.2 ± 0.2 14.7 ± 1.5 13.6 ± 0.4 12.1 ± 0.2 5.4 ± 0.6 [Co(cdacacen)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm 44.4 ± 1.2 37.7 ± 0.8 30.1 ± 0.3 19.8 ± 1.7 32.1 ± 0.4 28.9 ± 0.2 26.8 ± 0.5 15.20 ± 1.2 29.4 ± 1.4 26.1 ± 0.6 21.3 ± 0.3 12.1 ± 0.6 24.0 ± 0.1 21.4 ± 0.7 18.9 ± 1.1 10.1 ± 0.4 Table 3. The formation constants, (10-2 X Kf (M-1)) and the thermodynamic parameter values, AH°, AS°, AG° for [Co(cdacacen)(PBu3)]ClO4 • H2O with Im in different solvents at different temperature (K). ch3cn THF DMF EtOH Donor No 14.1 20.0 26.1 32 283 44.4 ± 1.2 23.6 ± 1.0 13.7 ± 0.9 10.4 ± 1.6 293 32.1 ± 1.4 15.8 ± 0.5 9.8 ± 0.6 8.7 ± 1.5 303 29.4 ± 1.4 12.4 ± 0.8 7.7 ± 0.8 6.6 ± 1.5 313 24.0 ± 1.1 10.2 ± 1.1 5.3 ± 0.2 4.8 ± 1.4 AH°/(kJ mol-1) -56.9 ± 3.2 -39.6 ± 4.6 -27.0 ± 1.8 -14.7 ± 1.2 AS°/(J K-1mol-1) -96.6 ± 4.5 -50.6 ± 6.8 -23.6 ± 2.7 -6.5 ± 3. 8 AG°/(kJ mol-1 )a -22.3 ± 1.3 -20.8 ± 2.2 -20.2 ± 0.4 -13.70 ± 2.6 a at T = 303 K Esmaielzadeh et al.: Experimental and Computational Study ... Acta Chim. Slov. 2016, 63, 351-362 357 Table 4. The experimental Thermodynamic parameter values, AH°, AS° and AG° for Co(III) Schiff base complexes with various cyclic amines in Co (III) complexes Aff°/(kJmol) AS°/(J Kmol) AG°/(kJmol-1)a [Co(cdacCF3en)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm -27.1 ± 1.7 -25.2 ± 2.3 -18.9 ± 2.8 -15.3 ± 2.9 -33.0 ± 1.4 -22.7 ± 4.1 -20.5 ± 0.9 -9.3 ± 2.7 -17.2 ± 2.1 -18.9 ± 1.8 -17.0 ± 0.8 -12.5 ± 1.1 [Co(cdacPhen)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm -43.5 ± 6.8 -33.3 ± 1.7 -27.1 ± 1.0 -22.9 ± 4.4 -77.7 ± 3.2 -52.7 ± 5.1 -33.0 ± 0.7 -28.1 ± 3.6 -20.3 ± 2.5 -17.6 ± 3.1 -17.2 ± 3.9 -12.5 ± 4.2 [Co(cdacacen)(PBu3)]+ Im 2-MeIm 2-EtIm BzIm -56.9 ± 3.2 -40.4 ± 3.8 -38.6 ± 2.8 -31.3 ± 4.7 -96.6 ± 4.5 -62.7 ± 4.1 -60.6 ± 4.3 -53.3 ± 5.2 -22.3 ± 2.5 -21.4 ± 2.1 -19.0 ± 3.3 -15.2 ± 1.6 1 at T= 303 K CH3CN. enthalpy change values are negative because of bond formation in all reactions. The solvation effect for five- and six-coordinated complexes is not very different due to the same charge but it seems that the five-coordinated complex is better solvated because it is smaller and more polar than the six-coordinate complex. The solvation contribution for enthalpy change can be negative after the equilibrium. In all systems AH ° values are negative (Table 4). The value of the AS° and its sign are dependent on two factors: the difference in the number of the particles of the initial substances and the product complexes, and the liberation of the solvent molecules from the solvation shells.35 On the bases on first factor, the n for all studied system is -1. Concerning this factor the entropy decreases and its sign is negative. According to the second factor, the entropy change is increased, but the net entropy changes for all reactions are negative, which indicate that the both factors are important. 3. 3. Density Functional Analysis of the Cobalt(III) Complexes 3. 3. 1. Thermodynamic Parameters With Theoretical Calculation Now, theoretical investigations have much applicability in the investigation of chemical reactions and identification of the chemical compounds.36'37 The effect of the molecular structures on the chemical reactivity has been object of great interest in several disciplines of chemistry. The quantum chemical calculations have been widely used to study the reaction mechanism and to interpret the experimental results as well as to solve chemical ambiguities. They could be considered as complementary to or replacement for experimental method. This is useful approach to investigate the mechanism of reaction in the molecule and its electronic structure level and electronic parameters can be obtained by means of theoretical calculations using the computational methodologies of quantum chemistry. The advancement in methodology and implementations has reached a point where predicted properties of reasonable accuracy can be obtained from density functional theory (DFT) calculations. In the literature the DFT has a great accuracy in reproducing the experimental values in geometry, kinetic and thermodynamic properties of a molecular system.3839 In order to have a better understanding of the ther-modynamic properties of complexation between [Co(Chel)(PBu3)]+ and some cyclic amines, it is useful to consider the stability energy, enthalpy and entropy changes to these reactions by DFT methods. As mentioned before, the geometry optimization of the five- and six-coordinated cobalt(III) complexes was performed using DFT methods with B3LYP functional and the 6-311G** basis set in the gas phase. The optimized structure of [Co(cda-cacen)(PBu3)]+ and [Co(cdacacen)(PBu3)(Im)]+ complex along with labeling of atoms is shown in Figure 4. The results of the computation reported in Tables 5 and 6 demonstrate the H, S, G and AH, AS, AG thermodynamic parameters for each cobalt(III) complexes against the four cyclic amines. On the basis of the theoretical results, the formations of the six-coordinated complexes follow the sequence below: [Co(cdacCF3en)(PBu3)(amine)]+ > [Co(cdacPhen) (PBu3)(amine)]+ > [Co(cdacacen)(PBu3)(amine)]+ and for the amine donor are: Im > 2-MeIm > 2-EtIm > BzIm. From these results, the following conclusions can be made: i) The formation constant value (AEf) decreased from (-105.42) - (-99.84) J/mol in [Co(cdac-CF3en)(PBu3)(amine)]+ to (-42.17) - (-35.91) in [Co(cdacacen)(PBu3)(amine)]+, suggest that the trend of stability depend upon the donor or acceptor group on the ketones moiety. Esmaielzadeh et al.: Experimental and Computational Study ... 358 Acta Chim. Slov. 2016, 63, 351-362 Figure 4. The optimized structures of [Co(cdacacen)(PBu3)]+ (left) and [Co(cdacacen)(PBu3)(Im)]+ (right) complexes within numbering of atoms. Table 5. The computational Thermodynamic parameter values, H/(Hartree), G/(Hartree) and S/J K 1 mol 1 for Co(III) Schiff base complexes, various cyclic amines and Co(III)-amines in gas phase. ""-"----^^Thermodynamic CompoundT~;~-^Parameter H G S [Co(cdacCF3en)(PBu3)]+ -1568.1871 -1568.3721 240.65 [Co(cdacCF3en)(PBu3)(amine)]+ Co(III) - Im -1894.7561 -1894.9311 280.26 Co(III) - 2-MeIm -1894.7387 -1894.9294 278.73 Co(III) - 2-EtIm -1894.7312 -1894.9214 277.93 Co(III) - BzIm -1894.7068 -1894.9197 275.14 Amines Im 326.5690 326.5590 80.16 2-MeIm 326.5516 326.5573 79.41 2-EtIm 326.5441 326.5493 79.10 BzIm 326.5197 326.5476 76.71 [Co(cdacPhen)(PBu3)]+ -1426.6741 -1426.8923 231.25 Co(III) - Im -1674.8631 -1674.9711 247.16 Co(III) - 2-MeIm -1674.8489 -1674.9496 245.97 Co(cdacPhen)(PBu3)(amine)]+ Co(III) - 2-EtIm -1674.8410 -1674.9473 245.01 Co(III) - BzIm -1674.8390 -1674.9426 240.43 Amines Im 248.1890 248.0788 80.16 2-MeIm 248.1748 248.0573 79.41 2-EtIm 248.1669 248.0550 79.10 BzIm 248.1649 248.0503 76.71 [Co(cdacPhen)(PBu3)]+ -1106.3831 -1106.9911 205.17 [Co(cdacacen)(PBu3)(amine)]+ Co(III) - Im -1263.7491 -1263.8998 226.86 Co(III) - 2-MeIm -1263.7126 -1263.8590 221.11 Co(III) - 2-EtIm -1263.7111 -1263.8573 220.19 Co(III) - BzIm -1263.6846 -1263.8495 216.93 Amines Im 157.3660 156.9087 80.16 2-MeIm 157.3295 156.9087 79.41 2-EtIm 157.3280 156.8679 79.10 BzIm 157.3015 156.8662 76.71 Esmaielzadeh et al.: Experimental and Computational Study ... Acta Chim. Slov. 2016, 63, 351-362 359 ii) The negative value of enthalpy changes (AH) for all studied system indicates that the process is exothermic and suggesting that the bond formation between Co(III)-amine are fairly strong. From the theoretical revalues, we can find that the trends of AH and AEf for six-coordinated co-balt(III) complex formation are different than the experimental values, due to difference of the studied molecular state. The isolated molecules in gas phase are considered in the theoretical calculations, while the experimental results are related to solution state. iii) The entropy changes (AS) values for all reactions are negative, indicated that the entropy was responsible for the complexation process in all cases. The negative value of entropy also confirming that the complexes are formed spon-taneously.40 iv) The Gibbs free energy (AG) in the ground state for all complexation reactions showed that the thermodynamic stability trend of studied co-balt(III) complexes was: [Co(cdacCF3en)(PB-u3)(amine)]+ > [Co(cdacPhen)(PBu3)(amine)]+ > [Co(cdacacen)(PBu3)(amine)]+ and for the amine donor was: Im > 2-MeIm > 2-EtIm > BzIm. According to AG, these complexes take place at room temperature, so the most optimal conditions for stability of complexes relate to systems of unsaturated chemistry.41 In other hand, all the complex formation is the spontaneous reaction. 3. 3. 2. HOMO-LUMO Gap Energies and Chemical Hardness The highest occupied molecular orbital (HOMO) energies, the lowest unoccupied molecular orbital (LU-MO) energies and the energy gap for all five and six-coordinated cobalt(III) complexes were calculated with B3LYP in 6-311G** basis set. The results are given in Table 7. The molecular HOMO/LUMO picture of the [Co(cdacacen)(PBu3)(Im)]+ complexes are depicted in Figure 5. In analogy to other [Co(cdacacen)(PBu3)]+ (acceptor) - Im (donor) compounds the HOMO is mainly located on the Im moiety, whereas the LUMO is mostly locates on electron acceptor fragment. The chemical hardness is useful to rationalize the relative stability and reactivity of chemical compounds. There are large HOMO- LUMO gap in the hard compounds and more stable and less reactive than soft compounds having small HOMO-LUMO gap.42 The definitions of universal concepts of molecular structure stability and reactivity can be provided using DFT method. For definition of hardness g, following equation develo- ped,43 n = 1/ 2 (I - A) (6) where I and A are the vertical ionization energy and the vertical electron affinity respectively. According to the Koopman theorem,44 the ionization energy and electron affinity can be equalized through HOMO and LUMO orbital energies (EA = -£HOMO and IP = -£lumo). So, the hardness corresponds to the gap between HOMO and LUMO orbital. Hence, the larger HOMO-LUMO energy gaps the harder molecule. n = 1/ 2 (ELUMO - Ehomo) (7) As seen from Table 7, The large HOMO-LUMO energy gaps for [Co(cdacCF3en)(PBu3)(amine)]+ suggests that good stability and high chemical hardness for the titled complex. Indeed the chemical hardness of the [Co(cdacacen)(PBu3)(amine)]+ complex is smallest, which indicates that these complexes is more unstable than the other studied cobalt(III) complexes in gas phase respectively. Table 6. The computational Thermodynamic parameter values, AH°, AS° and AG° for Co(III) Schiff base complexes with various cyclic amines in gas phase. Co (III) complexes Aff°/(kJmol) AS°/(J K mol ) AG°/(kJmol) [Co(cdacCF3en)(PBu3)(amine)]+ Im 2-MeIm 2-EtIm BzIm -28.1614 -25.6829 -25.2011 -17.7726 -80.7311 -79.7716 -79.0016 -78.6413 -30.5470 -28.8412 -28.7320 -27.9695 [Co(cdacPhen)(PBu3)(amine)]+ Im 2-MeIm 2-EtIm BzIm -16.8187 -14.9312 -14.0925 -13.1790 -56.0121 -51.4311 -50.9743 -48.2116 -24.0891 -21.9654 -20.9717 -17.7614 [Co(cdacacen)(PBu3)(amine)]+ Im 2-MeIm 2-EtIm BzIm -10.7277 -8.6364 -8.0012 -6.1713 -42.1615 -38.8050 -36.1209 -32.9109 -17.8417 -14.1618 -13.7893 -11.9817 Esmaielzadeh et al.: Experimental and Computational Study ... 360 Acta Chim. Slov. 2016, 63, 351-362 a) b) c) d) ted at B3LYP/6-311G** level. Table 7. The computed electronic properties of Co(III) complexes with B3LYP/6-311G** level. Co (III) complexes amine HOMO/eV LUMO/eV gap/eV Hardness [Co(cdacCF3en)(PBu3)(amine)]+ Im -0.264 -0.073 0.191 0.095 2-MeIm -0.238 -0.056 0.182 0.091 2-EtIm -0.221 -0.042 0.179 0.089 BzIm -0.206 -0.028 0.172 0.086 [Co(cdacPhen)(PBu3)(amine)]+ Im -0.198 -0.056 0.142 0.071 2-MeIm -0.183 -0.044 0.139 0.069 2-EtIm -0.176 -0.039 0.137 0.068 BzIm -0.170 -0.035 0.135 0.067 [Co(cdacacen)(PBu3)(amine)]+ Im -0.170 -0.038 0.132 0.066 2-MeIm -0.156 -0.029 0.127 0.063 2-EtIm -0.152 -0.029 0.123 0.061 BzIm -0.148 -0.027 0.121 0.060 Figure 5. Molecular orbital surfaces for the HOMO and LUMO of the [Co(cdacacen)(PBu3)] (a,b) and [Co(cdacacen)(PBu3)(Im)] (c,d) compu Esmaielzadeh et al.: Experimental and Computational Study ... Acta Chim. Slov. 2016, 63, 351-362 361 4. Conclusions In summary, the formation constants and the thermodynamic parameters for the complexation of five-coordinated cobalt(III) complexes as acceptors with imidazol and their derivatives as donors were determined experimentally based on spectrochemically and theoretically based on popular DFT methods including B3LYP and 6-311G** level of theory. The trend of the reactivity of titled cobalt(III) Schiff base complexes toward a given amine in experimental and computational studies is as follows: [Co(cdacacen)(PBu3)]+ > [Co(cdacPhen)(PBu3)]+ > [Co(cdacCF3en)(PBu3)]+ and [Co(cdacCF3en)(PBu3)]+ > [Co(cdacPhen)(PBu3)]+ > [Co(cdacacen)(PBu3)]+. This difference was due to molecular state. The following binding trend of the donors toward a given cobalt(III) complexes is sequences Im > 2-MeIm > 2-EtIm > BzIm. The five-coordinated cobat(III) complexes was found to be more stable in solvent with higher donor number, So the trend of the reactivity of studied complexes toward donor according to the different solvents is as follows: CH3CN > THF > DMF > EtOH. The thermodynamic parameters as important values for stability index revealed high chemical reactivity of synthesized compound in chemical reaction. A comparison between the calculated results and experimental results are used to validate the conclusion. 5. Acknowledgements We are grateful to Islamic Azad University, Darab branch Research Council for their financial support. 6. References 1. Y. Katayama, K. Hashimoto, H. Nakayama, H. Mino, M. No-jiri, T. Akiono, H. Nyunoya, M. Yohda, K. Takio, M. Odaka, J. Am. Chem. Soc. 2006, 128, 728-729. http://dx.doi.org/10.1021/ja057010q 2. B. Hu, Ch. Sun, Q. Deny, Z. Liu, J. Incl. Phenom. Ma-crocycl. Chem. 2013, 76, 345-352. http://dx.doi.org/10.1007/s10847-012-0205-x 3. M. Khorshidifar, H. Amiri Rudbari, B. Askari, M. Sahihi, M. Riahi Farsani, F. Jalilian, G. Bruno, Polyhedron 2015, 95, 1-13. http://dx.doi.org/10.1016Zj.poly.2015.03.041 4. C. M. da Silva, D. L. da Silva, L. V. Modolo, R. B. Alves, M. A. de Resende, C. V. B. Martins, A. de Fatima, J. Adv. Res. 2011, 2, 1-8. http://dx.doi.org/10.1016/jjare.2010.05.004 5. B. M. Alzoubi, G. Liehr, R. Eldik, Inorg. Chem. 2004, 43, 6093-6100. http://dx.doi.org/10.1021/ic049761j 6. Y. Zhang, W. Ruan, Y. Zhao, H. Wang, Z. Zhu, Polyhedron 2003, 22, 1535-1545. http://dx.doi.org/10.1016/S0277-5387(03)00261-4 7. N. K. Chaudhary, P. Mishra, Am. J. Appl. Chem. 2014, 2, 1926. http://dx.doi.org/10.11648/j.ajac.20140201.15 8. X. Rang, L. Wang, D. Cao, Y. Lin, J. Hao, Appl. Organomet. Chem. 2011, 25, 9-15. http://dx.doi.org/10.1002/aoc.1680 9. E. L. Chang, C. Simmers, D. A. Knight, Pharmaceuticals 2010, 3, 1711-1728. http://dx.doi.org/10.3390/ph3061711 10. T. C. Zeyrek. J. Korean. Chem. Soc. 2013, 57, 461-471. 11. R. Vafazadeh, S. Bidaki, Acta Chim. Slov. 2014, 61, 153- 160. 12. S. Esmaielzadeh, L. Azimian, K. Shekoohi, H. Esfandiari, M. Asadi, Z. Zare, A. R. Nejad, K. Mohammadi, Inorg. Chim. Acta 2013, 405, 155- 162. http://dx.doi.org/10.1016/j.ica.2013.05.001 13. J. K. Labanowski, J. W. Andzelm, Density Functional Methods in Chemistry, Springer Verlag, New York, 1991. http://dx.doi.org/10.1007/978-1-4612-3136-3 14. J. Baker, J. Comput. Chem. 1986, 7, 385-395. http://dx.doi.org/10.1002/jcc.540070402 15. M. M. Francl, W. J. Pietro, W. J. Hehre, J. S. Binkle, M. S. Gordon, J. Chem. Phys. 1972, 77, 3645-3665. 16. A. D. Becke, Phys. Rev. A 1988, 38, 3098-3100. http://dx.doi.org/10.1103/PhysRevA.38.3098 17. C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785-789. http://dx.doi.org/10.1103/PhysRevB.37.785 18. N. C. Handy, D. J. Tozer, G. J. Laming, C. W. Murrary, R. D. Amos, Isr. J. Chem. 1993, 33, 331-344. http://dx.doi.org/10.1002/ijch.199300040 19. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, J. T. Vre-ven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gom-perts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Ma-lick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J.V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Pittsburgh PA, 2003. 20. Z. Szafran, R. M. Pike, M. M. Singh, Microscale Inorganic Chemistry, Willey, New York, 1991. 21. R. Vafazadeh, M. Kashfi, Bull. Korean. Chem. Soc. 2007, 28, 1227-1230. http://dx.doi.org/10.5012/bkcs.2007.28J.1227 22. M. Asadi, Z. Asadi, Trans. Met. Chem. 2007, 32, 387-392. http://dx.doi.org/10.1007/s11243-007-0188-4 23. A. A. Emara, Spectrochim. Acta, Part A. Mol. Biomol. Spect. 2010, 77, 117-125. http://dx.doi.org/10.1016/j.saa.2010.04.036 24. M. A. Ali, A. H. Mirza, M. H. S. A. Hamid, N. Aminath, P. V. Bernhardt, Polyhedron 2012, 47, 79-86. Esmaielzadeh et al.: Experimental and Computational Study ... 362 Acta Chim. Slov. 2016, 63, 351-362 http://dx.doi.org/10.1016/j.poly.2012.08.024 25. D. Sakthialatha, R. Rajavel, J. Chem. Pharma. Res. 2013, J, 57-63. 26. P. Bhowmik, M. G. B. Drew, S. Chattopadhyay, Inorg. Chim. Acta 2011, 366, 62-67. http://dx.doi.org/10.1016Zj.ica.2010.10.010 27. M. A. Ali, A. H. Mirza, W. Y. Ting, M. H. S. A. Hamid, P. V. Bernhardt, R. J. Butcher, Polyhedron 2012, 48, 167-173. http://dx.doi.org/10.1016/j.poly.2012.08.069 28. M. Asadi, S. Esmaielzadeh, K. Mohammadi, Acta Chim. Slov. 2009, J6, 927-935. http://dx.doi.org/10.1002/recl.19520711108 29. J. A. A. Ketelaar, C. Van De Stolpe, A. Coulsit, W. Dz Cubes, Rec. Trav. Chim. 1952, 71, 1104-1114. 30. G. Tauzher, G. Mestroni, A. Puxeddu, R. Costanzo, G. Costa, J. Chem. Soc. A 1971, 2504-2507. http://dx.doi.org/10.1039/j19710002504 31. M. Asadi, A. H. Kianfar, S. Torabi, K. Mohammadi, J. Chem. Thermodynamics 2008, 40, 523-528. http://dx.doi.org/10.1016/jjct.2007.08.003 32. G. L Miessler, D. A.Tarr, Inorganic Chemistry, Prentice-Hall, New Jersy; 1991. 33. K. Hofmann, The Chemistry of Hetero Cyclic Compounds: Imidazole and Its Derivatives, Part I, Interscience Publisher, Inc., New York, 1953. http://dx.doi.org/10.1002/9780470186541 34. Y. Marcus, The Properties of Solvent, John Wiley & Sons, New York, 1999. 35. S. Abrland, Helv. Chim. Acta 1967, J0, 306-318. http://dx.doi.org/10.1002/hlca.19670500138 36. M. Najafi, D. Farmanzadeh, E. Klein, M. Zahedi, Acta Chim. Slov. 2013, 60, 43-55. 37. S. Esmaielzadeh, L. Azimian, K. Shekoohi, K. Mohammadi, Spectrochim. Acta, Part A. Mol. Biomol. Spect. 2014, 133, 579-590. http://dx.doi.org/10.1016/j.saa.2014.05.095 38. H. P. Ebrahimi, J. S. Hadi, Z. A. Abdulnabi, Z. Bolandnazar, Spectrochim. Acta, Part A. Mol. Biomol. Spect. 2014, 117, 485-492. http://dx.doi.org/10.1016/j.saa.2013.08.044 39. R. D. Chirico, W. V. Steele, A. F. Kazakov, J. Chem. Thermodynamics 2015, 86, 106-115. http://dx.doi.org/10.1016/jjct.2015.02.008 40. P. Mishra. Int. J. Pharma. Sci. Rev. Res. 2010, 2, 87-97. 41. M. Oftadeh, M. Moghadary, M. Soleimannejad, A. Semnani, Acta. Chim. Slov. 2013, 60, 95-104. 42. N. Özbek, G. Kavak, Y. Özcan, S. Ide, N. Karacan, J. Mol. Struct. 2009, 919, 154-159. http://dx.doi.org/10.1016/j.molstruc.2008.09.010 43. R. G. Pearson, J. Chem. Ed. 1987, 64, 561-567. http://dx.doi.org/10.1021/ed064p561 44. T. Koopmans, Polyhedron 1933, 1, 104-113. Povzetek Sintetizirali smo nekaj kobaltovih(III) kompleksov s potencialno štirivezno nesimetrično NNOS Schiffovo bazo kot li-gandom ter jih okarakterizirali z uporabo IR, *HNMR in UV-Vis spektroskopije ter elementne analize. Ravnotežne konstante so bile določene spektrofotometrično kot 1:1 adukt, ki nastane med kobaltovim(III) kompleksom z nekaterimi cikličnimi amini v acetonitrilu kot topilu pri konstantni ionski moči (I = 0.1 M NaClO4) ter pri različnih temperaturah. Nadalje, geometrije osnovnega stanja so bile izračunane z uporabo teorije gostotnostnega funkcionala (DFT) na B3LYP/6-311G** nivoju. Vezne energije, termodinamski parametri, strukturni parametri in elektronske strukture so bile raziskane. Teoretično proučevanje je bilo izvedeno za primerjavo z eksperimentalnimi podatki. Naša primerjava med računskimi in eksperimentalnimi rezultati razkriva, da je kompleksiranje kobaltovega(III) iona spontan, eksotermen proces, ki je entropijsko nezaželen. Esmaielzadeh et al.: Experimental and Computational Study ... DOI: I0.i7344/acsi.20i6.2337_Acta Chim. Slov. 2016, 63, 363-368_ 363 Scientific paper On Eccentric Connectivity Index of TiO2 Nanotubes Imran Nadeem and Hani Shaker* Department of Mathematics, COMSATS Institute of Information Technology, Defence Road, Off Raiwind Road, Lahore, Pakistan * Corresponding author: E-mail: hani.uet@gmail.com, imran7355@gmail.com Phone: +92-42-111001007, +92-321-4120429 Received: 12-02-2016 Abstract The eccentric connectivity index (ECI) is a distance based molecular structure descriptor that was recently used for mathematical modeling of biological activities of diverse nature. The ECI has been shown to give a high degree of predictability compare to Wiener index with regard to diuretic activity and anti-inflammatory activity. The prediction accuracy rate of ECI is better than the Zagreb indices in case of anticonvulsant activity. Titania nanotubular materials are of high interest metal oxide substances due to their widespread technological applications. The numerous studies on the use of this material also require theoretical studies on the other properties of such materials. Recently, the Zagreb indices were studied of an infinite class of titania (TiO2) nanotubes [32]. In this paper, we study the eccentric connectivity index of these nanotubes. Keywords: TiO2 nanotubes, Topological indices, Eccentric connectivity index 1. Introduction Cheminformatics is a new subject which is a combination of chemistry, mathematics and information science. It studies quantitative structure activity relationships (QSAR) and structure property relationships (QSPR) that are used to predict the biological activities and properties of chemical compounds. In the QSAR/QSPR study, physicochemical properties and topological indices are used to predict biological activity of the chemical compounds. A topological index is a numerical descriptor of the molecular structure based on certain topological features of the corresponding molecular graph. Topological indices are graph invariant and are a convenient means of translating chemical constitution into numerical values which can be used for correlation with physical properties in QSPR/QSAR studies.1-3 Topological indices are also used as a measure of structural similarity or diversity and thus they may give a measure of the diversity of chemical databases. There are two major classes of topological indices such as distance based topological indices and degree based topological indices. Among these classes, distance based topological indices are of great importance and play a vital role in chemical graph theory and particularly in chemistry. A graph G with vertex set V(G) and edge set E(G) is connected if there exists a path between any pair of vertices in G. The degree of a vertex u e V is the number of edges incident to u and denoted by deg(u). For two vertices u, v of a graph G their distance d (u, v) is defined as the length of any shortest path connecting u and v in G. For a given vertex u of G its eccentricity e(u) is the largest distance between u and any vertex v of G. Sharma et al.9 introduced a distance based topological index, the eccentric connectivity index (ECI) of G, defined as (1) It is reported in4-8 that ECI provides excellent correlations with regard to both physical and biological properties. The eccentric connectivity index is successfully used for mathematical models of biological activities of diverse nature. The simplicity amalgamated with high correlating ability of this index can easily be exploited in QSPR/QSAR studies.9-11 The prediction accuracy rate of ECI is better than the Wiener index with regard to diuretic activity12 and anti-inflammatory activity.13 Compare to Zagreb indices, the ECI has been shown to give a high degree of predictability in case of anticonvulsant activity.14 Recently, the eccentric connectivity index was studied for Imran Nadeem and Hani Shaker: On Eccentric Connectivity Index of TiO2 Nanotubes 364 Acta Chim. Slov. 2016, 63, 363-368 certain nanotubes15-19 and for various classes of graphs.20-22 The titanium nanotubular materials, called titania by a generic name, are of high interest metal oxide substances due to their widespread applications in production of catalytic, gas-sensing and corrosionresistance materials.23 As a well-known semiconductor with numerous technological applications, Titania (TiO2) nanotubes are comprehensively studied in materials science.24 The TiO2 nanotubes were systematically synthesized using different met-hods25 and carefully studied as prospective technological materials. Theoretical studies on the stability and electronic characteristics of titania nanostructures have extensively been studied.26-28 The numerous studies on the use of titania in technological applications also required theoretical studies on stability and other properties of such struc- tures 29-31 Recently, M. A. Malik et al.32 studied the Zagreb indices of an infinite class of TiO2 nanotubes. In this paper, we study eccentric connectivity index of these nanotubes. Figure 2: The labeled vertices of TiO2[m,n] nanotube. In the molecular graph, G, of TiO2 nanotubes, we can see that 2 p- \ and a is odd; ¡f n > p~ I and n is even. (5) Proof. Consider G = TiO2[m,n]. With respect to the eccentricity of vertices, we have the following cases. Case 1. When p = 2n In this case the eccentricity of the vertices uij, is 3p + 2n + 1 where i = l,2n + 2. The eccentricity of each vertex in the remaining 2n rows is 4p. Hence Case 3. When n > p -1 and n is odd In this case the eccentricity of vertices ui;, v„ is same as the eccentricity of vertices u(2n+3 i)j, v(2n+3 i)j where i = 1,2, •••, n + 1. The eccentricity of these vertices in ith row is given by e(uij) = s(vii) = 3p+2n+2-i where i-1,2,■■■,« +1 f'(G) = £ deg(v)£(v) ref(G) - 2(2/7}(2)(3/? + 2n + ]) + 2(2p)(4)0p + 2r7 + \) + (2p)(2n)(3)(4p) + (2p)(2n)(5)(,4p) + 2p(2n + 2){2)(4p) = 160 p-n + 48 pn + 104 p2 + 24 p. (10) (6) Case 2. when ^ < » < p -1 and p ^ 2n In this case the eccentricity of the vertices «,.,, v„ is v j same as the eccentricity of vertices u(2n+3 i)j, v(2n+3 ijj. where i = 1,2, •••, 2n - p + 1. The eccentricity of these vertices in ith row is given by Also, the eccentricity of the vertices xijt yijt x(i+1)J, y^j is same as the eccentricity of the vertices x(2n+3i)j, y(+n+3-iff X(2n+2-i)j , y(2n+2-i)j where i = 1,2 (n + 1)/2. The eccentricity of these vertices in ith row is given by e(xu) = £(yi/)=3p+2n+2-2i where / = 1,2,■ -(re +1)/2 (11) (7) The eccentricity of vertices uij, vij in remaining 2p - ij ij 2n rows is 4p. Also, the eccentricity of the vertices xij, yij, X(i+1)j, y(i+j j is same as the eccentricity of the vertices x(2n+3i)j, y (2n+3-ij X(2n+2-i)j, y(2n+2-i)j where i = 1,2, "', (2n - p)/2 The eccentricity of these vertices in ith row is given by The shortest paths having maximal length in Ti-O2[8,7] nanotube are shown in Figure 3. Hence = 2(2 pX2)(3 p +2n+1) + 2(2 />)(4}(3 p + 2n +1) + s(x:j ) = e{ys ) = 3p + 2n + 2 - 2/ where f = 1j2,--,(2b- p)/2 (8) The eccentricity of the vertices xij, yij in the remai- ij ij ning (2p - 2n + 2) rows is 4p. Hence ie(G)= £ deg(v)£(v) veK(G) = 2(2p)(2)(3p + 2n + l) + 2(2p)(4){3/;> + 2» + l) + 2(2p){3) £ (3p + 2n + 2-i) + 2(2/0(5) Z (3p + 2n + 2-i) + (2p)(2p~2„)0)(4p) + {2p)(2p-2n)(5)(4p) ¡-i {2a-pV2 + 4(2p)(2) X (3p + 2n + 2-2i) + (2p)(2p-2n + 2)(2)(4p) ¡=i = 28/>1+48paflf+l \2pn2 + )28pn + 64p2 +24p = 120 p2n + 68 pn2 +U2pn+96p2 + 52 p (12) (9) Imran Nadeem and Hani Shaker: On Eccentric Connectivity Index of TiO2 Nanotubes 366 Acta Chim. Slov. 2016, 63, 363-368 Figure 3: The shortest paths having maximal length in TiO2[8,7] nanotube. Case 4. When n > p - 1 and n is even In this case the eccentricity of vertices uij, v. is same v v as we discussed in case 3. Also, the eccentricity of the vertices xtj, yVj, x(i+1)j, y(i+1)j is same as the eccentricity of the vertices ^-j ydn+l-iff X(2n+2-i)j , y(2n+2-i)j where V = 1,2 •••, n/2. The eccentricity of these vertices in ith row is given by e(x,) = e{y,) = 3p + 2n + 2-2t where / = 1,2,-■ -,nj2 (13) The eccentricity of the vertices xij, yij in the remaining 2 rows is 4p. Hence = 2(2p)(2)Op + 2n + ]) + 2(2p)(4)(lp + 2n + \) + J^(3p+2n + 2-2i)+2(2p)(2)(4p) Theorem 2.3 Let TiO2[m,n] be the graph of titania nanotube, where m = 2p then for p odd we have In this case the eccentricity of the vertices uij, vij is ij ij "(2n+3-ij V(2n+3-i)j. where i = 1,2. The eccentricity of these vertices in ith row is gi- Case 1. When p = 2n - 1 In this case the ecc same as the eccentricity of vertices u re i = 1 ven by The eccentricity of vertices u., vij in remaining 2n rows is 4p. Also, the eccentricity of the vertices x1;, y1;. is same as the eccentricity of vertices x(2n+2)j X(2n+2j. The eccentricity of the vertices x., y1j is given by £(*i;) = «fry) = + 2n + 1 (17) The eccentricity of the vertices x.., y.. in the remai- ij ij ning 2n rows is 4p. The shortest paths having maximal length in TiO2[14,4] nanotube are shown in Figure 4. Figure 4: The shortest paths having maximal length in TiO2[14,4] nanotube. Hence ?{G) = X deg(vMv) + 2(2p)(3)(3p + 2 n) + 2(2p)(5)(3p + 2 n) (18) + 2(2p)(2)(3p + 2n + \) + (2p){2n){2)(4p) Case 2. when ^ < n < p - 1 and p^2n-l In this case the eccentricity of the vertices uijt v;. is same as we discussed in Case 2 of Theorem 2.2. The eccentricity of the vertices x., y1j, x(2n+2)j x(2n+2)j is same as we discussed in Case 1. (15) Proof. Consider G = TiO2[m,n]. With respect to the eccentricity of vertices, we have the following cases. Imran Nadeem and Hani Shaker: On Eccentric Connectivity Index of TiO2 Nanotubes Acta Chim. Slov. 2016, 63, 363-368 367 Also, the eccentricity of the vertices x(i+1);., y(i+1j, x(i+2)j y(i+2j is same as the eccentricity of the vertices x(2n.i)j> y(2n+2-ijj' X(2n+l-i)j, y^nyl-ij Where i = 1,2, '", 2 -P - 1)/2. The eccentricity of these vertices in (i y 1)th row is given by e(x{Mii ) = «(JV+Dj) = 3p + 2« +1 - 2i where / = 1,2,---,{2« - p—1)/ 2 (19) The eccentricity of the vertices x., y. in the remaining (2p - 2n + 2) rows is 4p. Hence p - 1 and n is odd In this case the eccentricity of the vertices ui., v..,x,., ij ij 1 j y1j., x(2ny2)j x(2ny2)j is same as we discussed in Case 2. Also, the eccyitritity of the vertices x(i+1)j, y(i+Dj, x(i+2)j, y(i+2)jis same as the eccentricity of the vertices x(2ny2_ijj, y(2ny2-i)j, x(2n+1-i)j, y(2n+1-i)j where i = 1,2 (n - 1)/2. The eccentricity of these vertices in (i y 1)th row is given by Hence ?{G) = £ deg(v)£(v) (21) 3. Conclusion The eccentric connectivity index provides excellent prediction accuracy rate compare to other indices in certain biological activities of diverse nature such as diuretic activity, anticonvulsant activity and anti-inflammatory activity. In this sense, this index is very useful in QSPR/QSAR studies. In this paper, we study eccentric connectivity index of an infinite class of TiO2 nanotubes. By using this index, we can find mathematical models of certain biological activities for this material. With the help of these models, we can predict about certain biological activities for this material. = 2{2p){2)Op + 2n + \) + 2{2p){A)Qp + 2n + \) + 2{2p)Q)Yj<^P+'in + 2-i) (U-IK2 (22) +2(2p){5)Ypp + 2n + 2~i) + 2{2p)(2)Qp + 2n + \) + 4(2p)(2) £ (3p +2« +1-2i) M M = \20 p2n +60 pn~ + 12pn + 12p2 + 28 p Case 4. When n > n - 1 and n is even. In this case the eccentricity of the vertices x^., y(i+1)j, x(iy2)j y(iy2j is same as the eccentricity of the vertices x(2n+2-i)r y^-j x(2n+1-i)j, y^n+l-ij where i = 1,2, "', n/2. The eccentricity of these vertices in (i y 1)th row is given by 4. References 1. J. V. de Julian-Ortiz, C. de Gregorio Alapont, I. Rios-Santa-marina, R. Garrcia-Domenech, J. Mol. Graphics Mod. 1998, 16, 14-18. http://dx.doi.org/10.1016/S1093-3263(98)00013-8 2. L. B. Kier, L. H. Hall, Res. Studies Press, Letchworth, 1986. 3. L. Pogliani, Croat. Chem. Acta. 1997, 3, 803-817. 4. A. K. Madan, H. Dureja, in: I. Gutman, B. Furtula (Eds.), Imran Nadeem and Hani Shaker: On Eccentric Connectivity Index of TiO2 Nanotubes 368 Acta Chim. Slov. 2016, 63, 363-368 Novel Molecular Structure Descriptors Theory and Applications II, University of Kragujevac, 2010, 91-138. 5. A. Ilic, I. Gutman, B. Furtula (Eds.), Novel Molecular Structure Descriptors-Theory and Applications II, University of Kragujevac, 2010, 139-168. 6. A. R. Ashrafi, M. Ghorbani, in: I. Gutman, B. Furtula (Eds.), Novel Molecular Structure Descriptors-Theory and Applications II, University of Kragujevac, 2010, 169-182. 7. T. Doslic, M. Saheli, in: I. Gutman, B. Furtula (Eds.), Novel Molecular Structure Descriptors Theory and Applications II, University of Kragujevac, 2010, 183-192. 8. A. K. Madan, H. Dureja, in: I. Gutman, B. Furtula (Eds.), Novel Molecular Structure Descriptors-Theory and Applications II, University of Kragujevac, 2010, 247-268. 9. V. Sharma, R. Goswami, A. K. Madan, J. Chem. Inf. Comput. Sci. 1997, 57, 273-282. http://dx.doi.org/10.1021/ci960049h 10. H. Dureja, A. K. Madan, Med. Chem. Res. 2007, 16, 331-341. http://dx.doi.org/10.1007/s00044-007-9032-9 11. V. Kumar, S. Sardana, A. K. Madan, J. Mol. Model. 2004, 10, 399-407. http://dx.doi.org/10.1007/s00894-004-0215-8 12. S. Sardana, A. K. Madan, MATCH Commun. Math. Comput. Chem. 2001, 43, 85-98. 13. S. Gupta, M. Singh, A. K. Madan, J. Math. Anal. Appl. 2002, 266, 259-268. http://dx.doi.org/10.1006/jmaa.2000.7243 14. S. Sardana, A. K. Madan, J. Comput.-Aided Mol. Des. 2002, 16, 545-550. http://dx.doi.org/10.1023/A:1021904803057 15. A. R. Ashrafi, M. Saheli, M. Ghorbani, J. Comput. Appl. Math. 2011, 235, 4561-4566. http://dx.doi.org/10.1016Zj.cam.2010.03.001 16. A. R. Ashrafi, T. Doslic, M. Saheli, MATCH Commun Math Comput Chem. 2011, 65(1), 221-230. 17. A. Iranmanesh, Y. Alizadeh, MATCH Commun Math Comput Chem. 2013, 69, 175-182. 18. M. Saheli, A. R. Ashrafi, Mace. J. of Chem and Chemical Eng. 2010, 29(1), 71-75. 19. N. P. Rao, K. L. Lakshmi, Digest J. of Nano. and Bio. 2010, 6(1), 81-87. 20. A. Ilic, I. Gutman, MATCH Commun. Math. Comput. Chem. 2011, 65, 731-744. 21. M. J. Morgan, S. Mukwembi, H. C. Swart, Discrete Math. 2011, 311, 1234-1299. http://dx.doi.org/10.1016/j.disc.2009.12.013 22. B. Zhou, Z. Du, MATCH Commun. Math. Comput. Chem. 2010, 63, 181-198. 23. J. Zhao, X. Wang, T. Sun, L. Li, Nanotechnology, 2005, 16(10), 2450-2454. http://dx.doi.org/10.1088/0957-4484/16/10/077 24. D. V. Bavykin, J. M. Friedrich, F. C. Walsh, Adv. Mater. 2006, 18(21), 2807-2824. http://dx.doi.org/10.1002/adma.200502696 25. W. Wang, O. K. Varghese, M. Paulose, C. A. Grimes, J. Mater. Res. 2004, 19, 417-422. http://dx.doi.org/10.1557/jmr.2004.19.2.417 26. R. A. Evarestov, Y. F. Zhukovskii, A. V. Bandura, S. Pisku-nov, Cent. Eur. J. Phys. 2011, 9(2), 492-501. 27. V. V. Ivanovskaya, A. N. Enyashin, A. L. Ivanovskii, Russ. J. Inorg. Chem. 2004, 49, 244-251. 28. A. N. Enyashin, G. Seifert, Phys. Stat. Sol. 2005, 242(7), 1361-1370. http://dx.doi.org/10.1002/pssb.200540026 29. A. E. Vizitiu, M. V. Diudea, Studia Univ. Babes- Bolyai, 2009, 54(1), 173-180. 30. Y. Q. Wang, G. Q. Hu, X. F. Duan, H. L. Sun, Q. K. Xue, Chem. Phys. Lett. 2002, 365, 427-431. http://dx.doi.org/10.1016/S0009-2614(02)01502-6 31. Y. Zhu, H. Li, Y. Koltypin, Y. R. Hacohen, A. Gedanken, Chem. Commun. 2001, 24, 2616-2617. http://dx.doi.org/10.1039/b108968b 32. M. A. Malik, M. Imran, Acta Chim. Slov. 2015, 62, 973-976. http://dx.doi.org/10.17344/acsi.2015.1746 Povzetek Med molekulske strukturne deskriptorje spada tudi »eccentric connectivity« indeks (ECI), ki je bil pred kratkim uporabljen za matematično modeliranje raznovrstnih bioloških aktivnosti. V primerjavi z Wienerjevim indeksom, daje ECI visoko stopnjo predvidljivosti v primeru diuretične in protivnetne aktivnosti. Stopnja natančnosti napovedi indeksa ECI je boljša od zagebškega indeksa v primeru antikonvulzivne aktivnosti. Med kovinskimi oksidi predstavljajo nanocevke Ti-O2 material, ki ima veliko tehnološko uporabnost. Številne študije tega materiala zahtevajo tudi teoretične študije njegovih lastnosti. Nedavno je bil za nanocevke TiO2 določen zagrebški indeks, v tem prispevku pa preučujemo indeks ECI. Imran Nadeem and Hani Shaker: On Eccentric Connectivity Index of TiO2 Nanotubes DOI: I0.i7344/acsi.20i6.2373_Acta Chim. Slov. 2016, 63, 369-375_ 359 Scientific paper Oxidation of Ruthenium and Iridium Metal by XeF2 and Crystal Structure Determination of [Xe2F3][RuF6]-XeF2 and [Xe2F3][MF6] (M = Ru, Ir) Melita Tramšek*, Evgeny Goreshnik and Gašper Tavčar Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia * Corresponding author: E-mail: melita.tramsek@ijs.si Received: 23-03-2016 Abstract Salts containing [Xe2F3]+ cations and [MF6]- anions (M = Ru, Ir) were synthesized by the oxidation of metal with excess of XeF2 in anhydrous hydrogen fluoride (aHF) as a solvent. Single crystals of [Xe2F3][RuF6]-XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6] were grown by slow evaporation of the solvent. [Xe2F3][RuF6]-XeF2 crystallizes in a triclinic P-1 space group (a = 8.3362(1) À, b = 8.8197(2) À, c = 9.3026(4) À; a= 68.27(1)°, /J = 63.45(1)°, y= 82.02°, V = 568.09(9) Â3 (Z = 2)). Discrete [Xe2F3]+, XeF2 and [RuF6]- units are found in the asymmetric unit. [Xe^][RuF6] and [Xe2F3][IrF6] compounds are isostructural and crystallize in a monoclinic Cc space group (a = 14.481(3) À (Ru); 14.544(3) À (Ir); b = 8.0837(8) À (Ru), 8.0808(7) À (Ir), c = 10.952(2) À (Ru), 11.014(2) À (Ir); P = 136.825(6)° (Ru), 139.954(7)°, V = 877.2(3) À3 (Ru), 883.6(3) À3 (Ir); Z = 4). The asymmetric unit in the [Xe2F3][MF6] (M = Ru, Ir) consists of one [Xe2F3]+ and one [MF6]- unit. Keywords: Noble gas fluorides, ruthenium, iridium, crystal structure 1. Introduction acterized. The compounds with composition 1:1 XeF2 is the most stable and easily handled noble gas (XeF+MF6) and 1:2 (XeF+M2F11 ) were obtained for the fluoride and therefore its chemistry is very extensive. Basic information about XeF2, its properties and the possibilities that it offers can be found in review paper and book and the references listed therein.12 One of its unexpected and interesting abilities is also binding to metal centres in order to form coordination compounds. A large variety of such compounds has been found in previous years.3 The formation of XeF2 adducts with main-group and transition-metal Lewis acidic pentafluoridometalates - MF5 is known for decades. So far three types of such compounds were found: 2XeF2 MF5, XeF2 MF5 and XeF2 (MF5)2. The degree of ionic character in these compounds varies depending on the Lewis acidity of the respective pentafluoride. Compounds were mainly characterized by vibrational spectroscopy and can be written as salts [Xe2F3][MF6], [XeF][MF6] and [XeF][M2F11], especially in the case of reactions with strong Lewis acids (for example AsF5, SbF5, BiF5 ...). The formation of 2:1 compounds was found in the cases where M was As, Sb, Bi, Ta, Ru, Os and Ir.4,5,6,7 From this type of compounds (2:1 composition) [Xe2F3][MF6] (M = As, Sb)8,9 were also structurally char- most of the MF5 mentioned above. Some of them were structurally characterized: [XeF][MF6] (M = As, Sb, Bi, Ru and Ir)10111213 and [XeF][M2F11] (M = Sb, Bi).11 One of the latest structurally characterized examples is also and [XeF][IrSbF11] with two different metals in the anion.13 [Xe2F3]+ and [XeF]+ cations were recently found with nonoctahedral anion in the xenon(II) polyfluoridoti-tanates(IV): [Xe2F3][Ti8F33] and [XeF]2[Ti9F38].14 The present study reports about the synthesis and structural characterization of three noble gas salts containing [Xe2F3]+ cation: [Xe2F3][RuF6]XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6]. 2. Experimental 2. 1. General Experimental Procedure and Reagents Volatile materials (anhydrous HF, F2) were handled in an all PTFE vacuum line equipped with PTFE (polyte- Tramsek et al.: Oxidation of Ruthenium and Iridium Metal 370 Acta Chim. Slov. 2016, 63, 369-375 trafluoroethylene) valves. The manipulations of the nonvolatile materials were carried out in a glove-box (M. Braun). The residual water in the atmosphere within the glove-box never exceeded 1 ppm. The reactions were carried out in FEP (tetrafluoroethylene-hexafluoropropylene; Polytetra GmbH, Germany) reaction vessels (height 250-300 mm with inner diameter 16 mm and outer diameter 19 mm) equipped with PTFE valves and PTFE coated stirring bars. T-shaped reaction vessels from PTFE, which were constructed as described earlier, were used for the crystallization process.15 Prior to their use all reaction vessels were passivated with elemental fluorine. Fluorine was used as supplied (Solvay Fluor and Derivate GmbH, Germany). Anhydrous HF (Linde, 99.995%) was treated with K2NiF6 (Advance Research Chemicals, Inc.) for several hours prior to use. XeF2 was synthesized by photochemical reaction between Xe and F2.16 Caution: aHF, F2 and XeF2 must be handled with great care in a well-ventilated fume hood, and protective gear must be worn at all times. 2. 2. Synthesis and Characterization Procedures Synthetic procedures for the ruthenium and iridium compounds were the same. Metal powder (Ru: 0.215 g, 2.13 mmol, Ir: 0.430 g, 2.20 mmol) was added into a reaction vessel inside the glove-box. The aHF was condensed into the reaction vessel at -196 °C at the vacuum line. Large excess of XeF2 (mole ratio M : XeF2 was approximately 1:10) was weighed into another reaction vessel inside the glove-box. Anhydrous HF was added to the XeF2 and the reaction vessel was warmed up to room temperature. These two reaction vessels (one with the suspension of the metal, and another with dissolved XeF2) were attached in a T-shape manner and additional valve was used in order to provide completely closed system. The XeF2 solution was then poured into cold reaction vessel (-196 °C) with suspension of the metal powder (Ru, Ir). The reaction vessel was left to slowly warm up to room temperature. The solution turned immediately green in the case of ruthenium but the reaction with iridium proceeded at room temperature for several days (light gray solid product). Products of the oxidation were isolated by removal of aHF and excessive XeF2 under dynamic vacuum at room temperature. Several crystallization experiments were performed. In some cases the product of the oxidation of the metal with XeF2 was dissolved in aHF in a wider arm of the T-shaped crystallization vessel, while in the other additional XeF2 was added. Solution was then poured into narrow arm of the crystallization vessel and left to crystallize by a small temperature gradient used for slow evaporation of aHF. The Raman spectra were recorded at room temperature with a Horiba Jobin Yvon LabRam-HR spectrometer equipped with an Olympus BXFM-ILHS microscope and CCD detector. The samples were excited by the 632.8 nm emission line of a He-Ne laser. Samples for measurement were transferred into the quartz capillary inside glove-box. The crystallographic parameters and summaries of data collection for all compounds are presented in Table 1. Single-crystal data were collected on a Rigaku AFC7 dif-fractometer using graphite monochromatized MoKa radiation at 200 K. Crystals were immersed into perfuorinated oil in glove-box and further on selected under the microscope. An empirical multi-scan absorption correction was applied. All structures were solved by direct methods using SIR-9217 and SHELXS-97 programs (teXan crystallo-graphic software package of Molecular Structure Corporation)18 and refined with SHELXL-97 software,19 implemented in program package WinGX.20 Full-matrix least-squares refinements based on F2 were carried out for the positional and thermal parameters for all non-hydrogen atoms. The figures were prepared using DIAMOND 3.1 software.21 Further details of the crystal-structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany, on quoting the depository number: CSD-430805 for [Xe2F3][RuF6], CSD-430806 for [Xe2F3][IrF6] and CSD-430807 for [Xe2F3][RuF6]XeF2, respectively. 3. Results and Discussion The oxidation power of XeF2 was used in order to prepare previously mentioned Ru(V) and Ir(V) compounds. XeF2 dissolved in anhydrous hydrogen fluoride (aHF) was also used as selective inorganic fluorinating reagent for oxidation and fluorination of Ir and RuF3 almost three decades ago with final products being IrF5 and RuF5.22 Ruthenium metal was oxidized rapidly with vigorous reaction being observed during the warming of the reaction vessel from -196 °C to room temperature. A clear, slightly green solution was obtained. We used a slightly modified procedure for the preparation of the ruthenium compound ([Xe2F3][MF6]XeF2). The product was further used for the synthesis of [Ba(XeF2)5][RuF6]2.23 The same reaction with iridium proceeded for several weeks. The colour of the solution was red-brown at the beginning and after several days became slightly yellow with some grey precipitate -same as the solid product after its isolation. The grey solid obtained by the oxidation of Ir metal with XeF2 was re-dissolved in aHF and a clear, slightly green solution was obtained. Products of the reactions were also monitored by Raman spectroscopy, which shows (Figure 1) that in both cases the compound with composition [Xe2F3][MF6] nXeF2 (M = Ru, Ir, n is approx. 1 according to the mass balance of the reaction) were obtained. An alternative method used for the preparation of related compounds with Ru(V) (KRuF6, LiRuF6 ) and Ir(V) (KIrF6, LiIrF6) with al- Tramšek et al.: Oxidation of Ruthenium and Iridium Metal Acta Chim. Slov. 2016, 63, 369-371 375 kaline metals is the room temperature oxidation with elemental fluorine in the presence of Lewis base (KF) in aHF.24,25 One of the recently published ways to prepare soluble iridium compounds, which seems to be important for modern "urban mining", is the reaction of the metal with tetrafluorobromates (MBrF4; M = K, Rb, Cs).26 a) b) Figure 1. Raman spectra of [Xe2F3][RuF6]-XeF2 (a) and ^FJPrFJ^ (b) For solid XeF2 the band at 497 cm-1 is characteristic.27 The bands at 506 cm-1, 515 cm-1 in ruthenium compound and 506 cm-1 and 516 cm-1 in iridium compound can be attributed to the XeF2 weakly associated with [Xe2F3]+ cations and [MF6]- anions in the [Xe2F3] [MF6] XeF2 product. Similar positions and assignment of these bands were observed in some other cases in the system XeF2-MF5 (M = Sb, Ta, Nb). The weakly associated XeF2 was found in the melt of the compounds.28 "Free" XeF2 was also found in the compounds XeF2XeF6AsF5 and XeF22(XeF6)2(AsF5), where the Raman bands depend on the interaction of the so called "free" XeF2 molecule with cations and anions and consequential distortion of its shape. "Free" XeF2 in XeF2-2(XeF6)-2(AsF5) is probably in a completely symmetric environment, therefore the band assigned to it coincides with the symmetric stretching frequency in molecular XeF2 (497 cm-1). On the other hand Raman spectrum of XeF2XeF6AsF5 doesn't show a symmetric vibration of molecular XeF2 but two bands at 557 cm-1 and 429 cm-1 which represent a distorted XeF2 molecule meaning that XeF2 in this compound can be far from "free".29 Linear distortion of XeF2 was found also in the Raman spectrum of XeF2 • [XeF5] [RuF6].30 Bands at 578 cm-1 and 586 cm-1 in the ruthenium compound and bands at 578 cm-1 and 587 cm-1 in iridium compound can be confidently assigned to the Xe-Ft stretch vibrations of the [Xe2F3]+ cation. They are in the region that is characteristic for such vibrations (from ca. 575 cm-1 to 600 cm-1). The bands at 646 cm-1, 667 cm-1 and 265 cm-1 for the ruthenium compound and 662 cm-1 and 243 cm-1 for the iridium can be assigned to the vibration of the [MF6]- anions. Products with additional XeR are not stable under Figure 2: Raman spectra of the reaction mixture during the isolation of ruthenium compound on the vacuum system: a.) mixture of [Xe2F3][RuF6] •XeFj, [Xe2F3][RuF6] and [XeF][RuF6]; b.) mixture of [Xe2F3][RuF6] and [XeF] [RuF6]; c.) [XeF][RuF6]. Tramsek et al.: Oxidation of Ruthenium and Iridium Metal 372 Acta Chim. Slov. 2016, 63, 369-375 dynamic vacuum at room temperature. They release XeF2, which leads to the formation of the [Xe2F3][MF6] and further on to the [XeF][MF6] (M = Ru, Ir) compounds. According to the mass balance of the reactions and Raman spectra, the [XeF][MF6] (M = Ru, Ir) salts seem to be stable at room temperature under dynamic vacuum. Raman analysis of the slow removal of XeF2 under dynamic vacuum in the case of ruthenium is shown in Figure 2. In the spectrum shown on the Figure 2a (black colour) all three phases can be found: [Xe2F3][RuF6]XeF2, [Xe2F3][RuF6] and [XeF][RuF6]. With the release of the XeF2, phases [Xe2F3][RuF6] and [XeF][RuF6] are found (Figure 2b (blue colour)). Prolonged pumping on the vacuum system (overnight) ended up with [XeF][RuF6] as the only product. Position and the intensities of the bands for [Xe2F3][RuF6] and [XeF][RuF6] are in the agreement with those published previously.4 3. 1. Crystal Structure Determination of [Xe2F3][RuF6]-XeF2 and [Xe2F3][MF6] (M = Ru, Ir) Three compounds in this system were structurally characterized. Summary of crystal data and refinement re- sults for [Xe2F3][RuF6] XeF2 and [Xe2F3][MF6] (M = Ru, Ir) are presented in Table 1 and selected distances and angles are found in Table 2. Several unsuccessful attempts were made in order to prepare suitable single crystals of the [Xe2F3][IrF6]XeF2. So far we were only able to resolve the structure of [Xe2F3][IrF6]. The structure of [Xe2F3][RuF6] XeF2 consists of discrete [Xe2F3]+, XeF2 and [RuF6]- units (Figure 3). XeF2 molecules and [Xe2F3]+ cations are oriented roughly perpendicularly to each other. When viewed along (-3 -4 3) direction alternating cationic and anionic layers could be seen. Anions are separated by XeF2 molecules (Figure 4). The compound is structurally related to [Kr2F3][SbF6]KrF2 in which the crystal packing consists of alternating cation and equally populated anion/KrF2 layers.31 XeF2 molecules are nearly linear with distances being 1.980(7) and 1.992(7) A and angle F10-Xe-F11 of 178.9(4)°. [Xe2F3]+ cation exhibit a planar, V shape configuration with nearly symmetrical Xe-Ft bonds (2.139(7) and 2.152(7) A) and a Xe-Fb-Xe angle of 154.3(4)°. The [RuF6]- anions are slightly distorted octa-hedra with Ru-F bond distances in the range from 1.834(8) to 1.861(7) A. Table 1. Crystal data and structure refinement for [Xe2F3][RuF6]-XeF2 and Xe2F3MF6 (M = Ru, Ir) [Xe2F3][RuF6]XeF2 [Xe2F3][RuF6] [Xe2F3][IrF6] Empirical formula RuXe3Fjj RuXe2F9 IrXe2F9 Formula weight 703.94 534.67 625.8 Wavelength, MoKa 0.71069 À 0.71069 À 0.71069 À Crystal system, Space group triclinic monoclinic monoclinic P-1 Cc Cc Temperature, K 200 200 200 Unit cell dimensions a, Ä 8.3362(1) 14.481(3) 14.544(3) b, Ä 8.8197(2) 8.0837(8) 8.0808(7) c, Ä 9.3026(4) 10.952(2) 11.014(2) a, ° 68.27(1) 90 90 ß,° 63.45(1) 136.825(6) 136.954(7) Y, ° 82.02(2) 90 90 V, Ä3 568.09(9) 877.2(3) 883.6(3) Z 2 4 4 Calculated density, g/cm3 4.115 4.048 4.704 Absorption coeff., mm-1 10.289 9.477 22.745 F(000) 610 932 1064 Crystal size, mm 0.08x0.06x0.04 0.10x0.10x0.08 0.10x0.07x0.05 Colour colourless colourless colourless Theta range for data collection, deg 2.487-28.6986 3.2522-28.5637 3.1256-27.9323 Limiting indices -8 < h < 11, -10 < k -18 < h < 16, -10 < k -18 < h < 17, -6 < 11, -11 < l < 12 < 10, -8 < l < 14 < k < 10, -6 < l < 14 Measured reflections 2259 1174 1129 Used in refinement 1837 890 1074 Free parameters 137 111 111 Goodness-of-fit on F2 1.134 1.134 1.067 R indices R1 = 0.0608 R1 = 0.0371 R1 = 0.0382 wR1 = 0.1775 wR1 = 0.0849 wR1 = 0.0963 Largest diff. peak and hole, e Ä-3 1.758 and -3.063 1.579 and -1.236 1.699 and -2.329 Tramšek et al.: Oxidation of Ruthenium and Iridium Metal Acta Chim. Slov. 2016, 63, 369-373 375 Table 2. Selected distances (Â) and angles (°) in [Xe2F3][RuF6] XeF2, [Xe2F3][MF6] (M = Ru, Ir) [Xe2F3][RuF6] [Xe2Fj] ^FJ • XeF2 [RuF6] [IrF6] Xe1-F1 2.139(7) 2.09(1) 2.12(2) Xe2-F1 2.152(7) 2.17(1) 2.15(2) Xe1-F2 1.913(8) 1.90(2) 1.88(2) Xe2-F3 1.919(6) 1.92(2) 1.96(2) Xe3-F10 1.980(7) Xe3-F11 1.992(7) Xe1-F1-Xe2 154.3(4) 161.5(5) 161.3(8) F10-Xe3-F11 178.9(4) Figure 3. Asymmetric unit in [Xe2F3][RuF6]-XeF2 with thermal ellipsoids drawn at 50 % probability level. The Xe centres from both XeF2 and [Xe2F3]+ moieties interact with fluorine atoms from another structural units. The shortest F9 - Xe2in and F9 - Xe1 distances of 3.190(7) and 3.216(7) A respectively correspond to slightly elongated Ru1-F9 bond (1.861(7) A). There are four XeF2 molecules bound to one anion via Xe-F contacts of 3.301(7)-3.373(7) A. Terminal F2 and F3 atoms from each [Xe2F3]+ also form longer contacts with Xe centres from other cations. These contacts are slightly longer (from 3.219(7) to 3.278(8) A, correspondingly) than those in the case of XeF2 molecules. Weak Xe-F(Xe) and Xe-F(Ru) interactions connect above mentioned units into three-dimensional network (Figure 4) if contacts shorter than 3.4 A are taken into consideration. The sum of the van der Waals radius for xenon (2.16 A) and fluorine (1.35 A) is 3.51 A.32 eral Xe-F contacts in the range above 3 A can be found. A packing diagram along the b-axis is presented in Figure 6. A less bent structure of the [Xe2F3]+ cation is found in the case of [Xe2F3][MF6] (M = Ru, Ir) compared to the [Xe2F3][RuF6]XeF2. The Xe-Fb-Xe angle is 161.5(5)° in the ruthenium compound and 161.3(8)° in the iridium compound. These angles are in agreement with those in isostructural monoclinic [Xe2F3][SbF6] (Xe -Fb -Xe = 160.3 °). Bridging angle of Xe-Fb-Xe in [Xe2F3]+ cations vary from 139.8° as observed in trigonal [Xe2F3] [AsF6]9 to the widest one being 164.3° as observed in [Xe^irT^J.14 Strong dependence of the Xe-Fb-Xe bridge angle on the crystal packing and on the nature of the counter anion was demonstrated in a previous study. Calculation (Christiansen-Ermler ECP) in the same study also predicted non-linear structure of the [Xe2F3]+ cation with a bridging angle of 168°.9 Figure 5. Asymmetric units in [Xe2F3][RuF6] and [Xe2F3][IrF6] with thermal ellipsoids drawn at 50 % probability level. Figure 6. Packing diagram of [Xe2F3][RuF6] along b-axis. Figure 4. Packing diagram of [Xe2F3][RuF6]-XeF2. The [Xe2F3][MF6] (M = Ru, Ir) salts are both isostructural with monoclinic [Xe2F3][SbF6].9 Asymmetrical unit in both cases consists of one [Xe2F3]+ cation and one [MF6]- anion (Figure 5). In both cases sev- 4. Conclusions The oxidizing power of XeF2 was demonstrated by oxidation of ruthenium and iridium metal in aHF as a solvent. Products of the oxidation belong to the family of no- Tramsek et al.: Oxidation of Ruthenium and Iridium Metal 374 Acta Chim. Slov. 2016, 63, 369-375 ble gas compounds with [Xe2F3]+ cations. Salt with composition [Xe2F3][RuF6] ■ XeF2 was structurally characterized. The synthesis and characterization with Raman spectroscopy of the new salt [Xe2F3][IrF6]XeF2 are also reported. Single crystal structures of [Xe2F3][RuF6] and [Xe2F3][IrF6] were determined. 5. Acknowledgement The authors gratefully acknowledge the Slovenian Research Agency (ARRS) for financial support of the Research Program P1-0045 (Inorganic Chemistry and Technology). 6. References 1. M. Tramšek, B. Žemva, Acta Chim. Slov. 2006, 53, 105-116. 2. J. Reedjik, K. Poeppelmeier (Ed.): Comperhensive Inorganic Chemistry II, Elsevier, Oxford, 2013, D. S. Brock, G. J. Schrobilgen, B. Žemva, Vol. 1, pp755-822 3. M. Tramšek, G. Tavčar, J. Fluorine Chem. 2015, 174, 14-21. http://dx.doi.org/10.10167j.jfluchem.2014.08.009 4. F. O. Sladky, P. A. Bulliner, N. Bartlett, J. Chem. Soc. 1969, 2179-2188. http://dx.doi.org/10.1039/J19690002179 5. B. Frlec, J. H. Holloway, J. Chem. Soc. 1975, 535-540. 6. J. Gillespie, D. Martin, G. J. Schrobilgen, J. Chem. Soc. Dalton 1980, 1898-1903. 7. J. H. Holloway, J. G, Knowles, J. Chem. Soc. 1969, 756-761. http://dx.doi.org/10.1039/j19690000756 8. N. Bartlett, B. G. DeBoer, F. J. Hollander, F. O. Sladky, D. H. Templeton, A. Zalkin, Inorg. Chem. 1974, 13, 780-785. http://dx.doi.org/10.1021/ic50134a004 9. B. A. Fir, M. Gerken, B. E. Pointner, H. P. A. Mercier, D. A. Dixon, G. J. Schrobilgen, J. Fluorine Chem. 2000, 105, 159-167. http://dx.doi.org/10.1016/S0022-1139(00)00306-7 10. A. Zalkin, D. L. Ward, R. N. Biagoni, D. H. Tempelton, N. Bartlett, Inorg. Chem. 1978, 17, 1318-1322. http://dx.doi.org/10.1021/ic50183a044 11. H. St. A. Elliot, J. F. Lehman, H. P. A. Mercier, H. D. B. Jenkins, G. J. Schrobilgen, Inorg. Chem. 2010, 49, 8504-8523. 12. N. Bartlett, M. Gennis, D. D. Gibler, B. K. Morrell, A. Zalkin, Inorg. Chem. 1973, 12, 1717-1721. http://dx.doi.org/10.1021/ic50126a002 13. F. Tamadon, S. Seidel, K. Seppelt, Acta Chim. Slov. 2013, 60, 491-494. 14. K. Radan, E. Goreshnik, B. Žemva, Agew. Chem. Int. Ed. 2014, 53, 13715-13719. 15. M. Lozinšek, E. Goreshnik, B. Žemva, Acta Chim. Slov. 2014, 61, 542-547. 16. R. N. Grimes (Ed.). Inorganic Syntheses, John Wiley, New York, 1992, A. Šmalc, K. Lutar, Vol. 29, pp. 1-4. 17. A. Altomare, M. Cascarano, M., C. Giacovazzo, A. Guagliardi, J. Appl. Cryst. 1993, 26, 343-350. http://dx.doi.org/10.1107/S0021889892010331 18. Molecular Structure Corporation. (1997-1999), teXsan for Windows, Single Crystal Structure Analysis Software. Version 1.06, MSC, 9009 New Trails Drive, The Woodlands, TX 77381, USA. 19. G. M. Sheldrick, Acta Cryst. 2008, A64, 112-122. http://dx.doi.org/10.1107/S0108767307043930 20. L. J. Farrugia, J. Appl. Cryst. 1999, 32, 837-838. http://dx.doi.org/10.1107/S0021889899006020 21. DIAMOND v3.1, Crystal Impact GbR, Bonn, Germany, 2004-2005 22. R. C. Burns, I. D. MacLeod, T. A. O'Donnell, T. E. Peel, K. A. Philips, A. B. Waugh, J. Inorg. Nucl. Chem. 1977, 39, 1737-1739. http://dx.doi.org/10.1016/0022-1902(77)80193-0 23. T. Bunič, M. Tramšek, E. Goreshnik, B. Žemva, Collect. Czech. Chem. Commun. 2008, 73, 1645-1654. http://dx.doi.org/10.1135/cccc20081645 24. G. Lucier, S. H. Elder, L. Chacon, N Bartlett, Eur. J. Solid State Inorg. Chem. 1996, 33, 809-820. 25. G. Tavčar, B. Žemva, Inorg. Chem. 2013, 52, 4139-4323. http://dx.doi.org/10.1021/ic302323j 26. S. Ivlev, P. Woidy, F. Kraus, I. Gerin, R. Ostvald, Eur. J. Inorg. Chem. 2013, 4984-4987. http://onlinelibrary.wiley.com/doi/10.1002/ejic.201300618/ abstract 27. P. A. Agron, G. M. Begun, H. A. Levy, A. A. Mason, C. G. Jones, D. F. Smith, Science 1963, 139, 842-844. http://dx.doi.org/10.1126/science.139.3557.842 28. B. Frlec, J. H. Holloway, J. Inorg. Nucl. Chem. Supplement 1 1976, 28, 167-171. 29. N. Bartlett, M. Wechsberg, Z. anorg. Allg. Chem. 1971, 385, 5-17. http://dx.doi.org/10.1002/zaac.19713850103 30. B. Žemva, L. Golič, J. Slivnik, Vestn. Slov. Kem. Drus. 1983, 30, 365-376. 31. J. F. Lehman, D. A. Dixon, G. J. Schrobilgen, Inorg. Chem. 2001, 40, 3002-3017. http://dx.doi.org/10.1021/ic001167w 32. A. Bondi, J. Phys. Chem. 1964, 68, 441-451. http://dx.doi.org/10.1021/j100785a001 Tramšek et al.: Oxidation of Ruthenium and Iridium Metal Acta Chim. Slov. 2016, 63, 369-375 375 Povzetek Z oksidacijo kovine (Ru, Ir) s presežnim XeF2 v brezvodnem vodikovem fluoridu (aHF) kot topilu smo pripravili spojine s kationi [Xe2F3]+ in anioni [MF6]- (M = Ru, Ir). Kristale [Xe2F3][RuF6] • XeF2, [Xe2F3][RuF6] in [Xe2F3][IrF6], ki so bili primerni za rentgensko strukturno analizo, smo pripravili s počasnim izhlapevanjem topila. [Xe2F3][RuF6] • XeF2 kristalizira v triklinskem kristalnem sistemu; prostorska skupina P-1 (a = 8,3362(1) A, b = 8,8197(2) A, c = 9,3026(4) A; a= 68,27(1)°, P= 63,45(1)°, Y = 82,02°, V = 568,09(9) A3 (Z = 2)). V asimetrični enoti spojine se nahajajo [Xe2F3]+, XeF2 in [RuF6]-. Spojini [Xe2F3][RuF6] in [Xe2F3][IrF6] sta izostrukturni in kristalizirata v monoklinskem kristalnem sistemu; prostorska skupina Cc (a = 14,481(3) A (Ru); 14,544(3) A (Ir); b = 8,0837(8) A (Ru), 8,0808(7) A (Ir), c = 10,952(2) A (Ru), 11,014(2) A (Ir); P = 136,825(6)° (Ru), 139,954(7)°, V = 877,2(3) A3 (Ru), 883,6(3) A3 (Ir); Z = 4). Asimetrični enota [Xe2F3][MF6] (M = Ru, Ir) je sestavljena iz [Xe2F3]+ in [MF6]- ionov. Tramsek et al.: Oxidation of Ruthenium and Iridium Metal 376 _Acta Chim. Slov. 2016, 63, 376-379_doi: I0.i7344/acsi.20i6.2378 Scientific paper The Eccentricity Version of Atom-Bond Connectivity Index of Linear Polycene Parallelogram Benzenoid ABC5(P(n,n)) Wei Gao,1 Mohammad Reza Farahani2 and Muhammad Kamran Jamil3 * 1 School of Information Science and Technology, Yunnan Normal University, Kunming 650500, China. 2 Department of Applied Mathematics of Iran University of Science and Technology (IUST), Narmak, Tehran 16844, Iran. 3 Department of Mathematics, Riphah Institute of Computing and Applied Sciences (RICAS), Riphah International University, 14 Ali Road, Lahore, Pakistan. * Corresponding author: E-mail: m.kamran.sms@gmail.com Phone: +923464105447 Received: 23-02-2016 Abstract Among topological descriptors, connectivity indices are very important and they have a prominent role in chemistry. The atom-bond connectivity index of a connected graph G is defined as ABC(G) = y J1' '' where dv denotes the degree of vertex v of G and the eccentric connectivity index of the molecular graph G is defined as £(G) = x e(v ), where efv) is the largest distance between v and any other vertex u of G. Also, the eccentric atombond connectivity index of a connected graph G is equal to ABC5(G) = v In this present paper, we compute this new Eccentric Connectivity index for an infinite family of Linear Polycene Parallelogram Benzenoid. Keywords: Molecular graph, Atom-bond connectivity index; Eccentricity connectivity index, Linear Polycene Parallelogram Benzenoid 1. Introduction Let G = (V E) be a graph, where V(G) is a non-empty set of vertices and E(G) is a set of edges. In chemical graph theory, there are many molecular descriptors (or Topological Index) for a connected graph, that have very useful properties to study of chemical molecules.1-4 This theory had an important effect on the development of the chemical sciences. A topological index of a graph is a number related to a graph which is invariant under graph automorphisms. Among topological descriptors, connectivity indices are very important and they have a prominent role in chemistry. One of them is Atom-Bond Connectivity (ABC) index of a connected graph G = (V,E) and defined as (1) where dv denotes the degree of vertex v of G, that introduced by Furtula et.al.5'6 On the other hands, Sharma, Goswami and Madan7 (in 1997) introduced the eccentric connectivity index of the molecular graph G as i(G)=Yß, xs(v), (2) Gao et al.: The Eccentricity Version of Atom-Bond Connectivity Acta Chim. Slov. 2016, 63, 376-379 377 where e(u) is the largest distance between u and any other vertex v of G. If x,yeV(G), then the distance d(x,y) between x and y is defined as the length of any shortest path in G connecting x and y. In other words, is maximum distance with first-point v in G. e(v) = Max{d(v, u) | VveV(G)} (3) The Eccentric Connectivity polynomial of a graph G, was defined by Alaeiyan, Mojarad and Asadpour as follows:8,9 ECP(G,x)= Yj vef(G) ,ecc( V') (4) Alternatively, the eccentric connectivity index is the first derivative of ECP(G;x) evaluated at x = 1. Now, by combine these above topological indexes, we now define a new version of ABC index as:10 (5) cal index for an infinite family of Linear Polycene Parallelogram Benzenoid. 2. Main Results and Discussion In this section, we computed the Eccentric atombond connectivity index ABC5 of an infinite family of Linear Polycene Parallelogram of Benzenoid graph,19 by continuing the results from.8,9,18,19 This Molecular graph has 2n(n + 2) vertices and 3n2 + 4n -1 edges. For further study and more detail representation of Linear Polycene Parallelogram of Benzenoid P(n,n), see.8,9,18,19 Also, reader can see the general case of this Benzenoid molecular graph in Figure 1. The general representation of Linear Polycene Parallelogram of Benzenoid P(n,n) is shown in Figure1. Theorem 1. Let P(n,n) (VneN) be the Linear Polycene Parallelogram of benzenoid. Then the Eccentric atom-bond Connectivity index ABC5 of P(n,n) is equal to: ABCs{P(n, n))=4 I Sn-4i-l I Sjj—4r"-3 ^4r-2(4ii + ])i+4«(4« + l} +J4r-2(4n-l)i t4h(4h- Sn -4/ -S i_ I «»^¥-7__ 2(Kn-3)i + + : y4/!-2(Rn +!)/ +2(s«--lOil +3) MJJL+fa-ij^El-2(k-n1 4n*' (2)i+1) n Un -KJI + 5 (6) We denote this new index of a connected graph G (Eccentric atom-bond connectivity index) by ABC5(G) (Since it is fifth definition of ABC index). For more details about the Atom-Bond Connectivity and Eccentricity connectivity indices see paper series.11-18 The aim of this paper is to exhibit this new topologi- Proof: Let (Vn>1) P(n,n) depicted in Figure 1 be the general representation of Linear Polycene Parallelogram Benzenoid graph with 2n(n+2) vertices, such that 4n + 2 of them have degree two and 2n2-2 have degree three (V(P(n,n) = V2UV3). Thus there are 3n2+4n-1 (=V2[2(4n + 2) + 3(4n2-2)]) edges. Table 1. Eccentric connectivity index for all vertices of Linear Polycene Parallelogram Benzenoid graph P(n,n).8,9 2n+l 2n+l 2n+2 4n-5 4n-4 4n-3 4n-2 4n-l 2n 2n+l 2n+2 4n-5 4n-4 4n-3 4n-2 2n 2n+l 2n+2 ... 4n-5 4)1-4 2n 2n+l 2)i+2 2n 2n+l 2)i+2 2n+I Gao et al.: The Eccentricity Version of Atom-Bond Connectivity ... 378 Acta Chim. Slov. 2016, 63, 376-379 Figure 1. WneN the general representation of Linear Polycene Parallelogram of Benzenoid P(n,n) and the eccentric connectivity of its vertices. Now by refer to,8'9'16 we have the maximum eccentric connectivity and minimum eccentric connectivity for a veV(P(n,n)) as Max£(vj = 4n-1 andMine(vj=2n. Now by according to Figure 1 and Table 1, it is easy see that: • For all vertices with degree two in P(n,n), the ec- centricity are equal to 4n-1, 4n-2, 4n-4, 4n-6,..., 2n + 2, 2n + 1 . • For all other vertices with degree three P(n,n) (dv = 3), the eccentricity are equal to 4n-3 until 2n. Thus, we have following computations by using Figure 1 and results in Table 1 as: ABCs(P(n,n))= £ lfW+4')-2 y ßBH+ T pQH+ v M1') -•£('("»11 4'MV) «i'st|f(-j||) 40E(V) = I(4n-2i )+(4pi -2/ t l)-2 +4™-i (4)t-2(')+(4n-2t-l)-2 + (2h + f)+(2n +l)-2 (4n-2i )(4n -2i tI) ] (4,/-2i )(4«-2/-l) y (2m + 1)(2n +1) + y..,f , |(4»-2;-2)+(4,l-2/-lH+ , 12»)+(h). ^ ^ (4/t—2f —2){4«—2f—1) ^ 'if (4a-2/-2)(4n-2i-3) (2*)(2(i] (4a —2i —2){4n—2i -2 -2i -1J-2 (4n -2l )(4h-2; +1) L>~ l(4ii-2iX4«-2i-l)-2++ 8i/h (4a-2Ä-2i-l) (2m+1) +4Y-'ti) . n |(4»-2/)+(4n-2i -l)-2 + , fr (4«-2/ -2)(4ij-2i -1) ^ ^ (4m-2i)(4«-2i-l) 1 ' n l^y.-i ( 8«-4/ -3 + 8VB ^4/! -2(4w +l)/ +4M (4B +l) ^i"^4I:-2(4«-1}/ + 4«(4H-1) (2M+1) (7) $n-4i-5 4f i-2(8d -3)f+2(8i?-+l) 811-4/-1 n-1) -2(8i( + l)t+2(8H:-I0«+3) 1 Gao et al.: The Eccentricity Version of Atom-Bond Connectivity Acta Chim. Slov. 2016, 63, 376- 379 379 Finally, VneN, the fifth ABC index of Linear Polycene Parallelogram Benzenoid P(n,n) is equal to: (8) Here, we complete the proof of Theorem 1. ■ 3. Conclusions In this paper, we consider a family of Linear Polycene Parallelogram Benzenoid and compute the Eccentric atom-bond Connectivity index ABC5. The Eccentric atombond Connectivity index ABC5 was defined as ABCS(G) = £ JEEE^Hp, such that e(v) (Max{d(v, u)NVveV(G)}) is the largest distance between v and any other vertex u of G. 4. References 1. I. Gutman, N. Trinajsti}, Chem. Phys. Lett. 1972, 17, 535-538. http://dx.doi.org/10.1016/0009-2614(72)85099-1 2. D. A. Klarner, Polyominoes, In: J. E. Goodman, J. O'Rour-ke, (eds.) Handbook of Discrete and Computational Geometry, CRC Press, Boca Raton, 1997, 12, 225-242. 3. M. Randi}, J. Am. Chem. Soc. 1975, 97, 6609-6615. http://dx.doi.org/10.1021/ja00856a001 4. N. Trinajsti}, Chemical Graph Theory. CRC Press, Boca Raton, FL., 1992. http://dx.doi.org/10.1007/s10910-009-9520-x 5. D. Vukicevic, B. Furtula, J. Math. Chem. 2009, 46, 13691376. 6. E. Estrada, L. Torres, L. Rodriguez, I. Gutman, Indian J. Chem. 1998, 37A, 849-855. 7. V. Sharma, R. Goswami, A. K. Madan, J. Chem. Inf. Com-put. Sci. 1997, 37, 273-282. http://dx.doi.org/10.1021/ci960049h 8. M. Alaeiyan, R. Mojarad, J. Asadpour, Optoelectron. Adv. Mater.-Rapid Commun. 2011, 5, 761-763. 9. M. Alaeiyan, J. Asadpour, Optoelectron. Adv. Mater.-Rapid Commun. 2012, 6, 191-193. 10. M. R. Farahani, WorldAppl. Sci. J., 2013, 21, 1260-1265. 11. A. R. Ashrafi, M. Ghorbani, M. Hemmasi, Digest. J. Nano-mater. Bios., 2009, 4, 483-486. 12. S. Alikhani, M. A. Iranmanesh, Digest. J. Nanomater. Bios. 2011, 6, 253-257. 13. I. Gutman, O. E. Polansky, Mathematical Concepts in Organic Chemistry, Springer-Verlag, New York, 1986. http://dx.doi.org/10.1007/978-3-642-70982-1 14. M. A. Johnson, G. M. Maggiora, Concepts and Applications of Molecular Similarity, Wiley Interscience, New York, 1990. 15. M. R. Farahani, Acta Chim. Slov. 2012, 59, 779-783. 16. M. R. Farahani, Acta Chim. Slov. 2013, 60, 429-432. 17. M. R. Farahani, An. Univ. Vest Timis. Ser. Mat.-Inform. 2013, 51, 29-37. 18. M. R. Farahani, Int. Lett. Chem. Phys. Astron. 2014, 18, 57-62. 19. P. V. Khadikar, Iran. J. Math. Chem. 2010, 1, 7-42. Povzetek Med topološkimi deskriptorji so indeksi povezanosti izredno pomembni in imajo vidno vlogo v kemiji. Indeks atomske povezanosti grafa G je definiran kot ABC(G )= £ pli \ kjer je dv stopnja vozlišča (točke) v od G ter je ecentrični h. . h. ■. ■. V indeks povezanosti grafa G definiran kot Š(G)= *£(v). kjer je £(v) najdaljša razdalja med v in katerim koli voz- ■. j liščem u od G. Poleg tega je ecentrični indeks atomske povezanosti povezanega grafa G enak ABC5(G) = = y k") + *(> )-2 . V tem članku smo izračunali novi ecentrični indeks povezanosti za neskončno družino linearnih policenskih paralelo-gramskih benzenoidov. Gao et al.: The Eccentricity Version of Atom-Bond Connectivity ... 380 _Acta Chim. Slov. 2016, 63, 380-391_DOI: I0.i7344/acsi.20i6.2385 Scientific paper Comparative Photocatalytic Degradation of Monoazo and Diazo Dyes Under Simulated Visible Light Using »2 Fe3+/C/S doped-TiO2 Nanoparticles William Wilson Anku,* Samuel Osei-Bonsu Oppong, Sudheesh Kumar Shukla and Poomani Penny Govender* Department of Applied Chemistry, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, Johannesburg, South Africa. * Corresponding author: E-mail: pennyg@uj.ac.za, williamanku85@gamil.com Tel:+275596555 Received: 26-02-2016 Abstract This research work delved into the photocatalytic degradation of monoazo dye (methyl orange) and diazo dye (congo red) in aqueous solution using Fe3+/C/S-doped TiO2 nanocomposites. The nanocomposites were synthesised through sol-gel method and characterized using XRD, FTIR, SEM, TEM, EDX, BET and UV-Vis. Photocatalytic degradation of the dyes was monitored under simulated visible light using pristine TiO2, C/S/doped-TiO2 and Fe3+/C/S doped-TiO2 with varying concentrations of Fe3+. The influence of catalyst doping, solution pH, and light intensity were also examined. Doping TiO2 with Fe3+/C/S caused reduction in its band gap value with the resultant improvement in its visible light activity. The photocatalytic efficiency of the catalysts is given as follows: TiO2 < C/S/TiO2 < Fe3+/C/S-TiO2 with Fe3+/C/S-TiO2 (0.3% Fe3+) as the best performing photocatalyst. The monoazo dye experienced higher degradation efficiency than the diazo dye. Degradation of the azo dyes was observed to decrease with increasing pH from 2 to 12. Increased visible light intensity enhanced the photodegradation efficiency of the dye. Dye decolourization was observed to be faster than its mineralization. Keywords: TiO2, metals, non-metals, azo dyes, photocatalytic degradation, sol-gel method. 1. Introduction The release of dye polluted wastewater by textile industries into surface water is causing serious environmental challenges. These challenges are not only limited to the aesthetic impact on the water bodies, the negative effect on aquatic plants and death of fish but also the health effects posed to humans, as many of these dyes are toxic and carcinogenic.1,2 A large number of dyes with varied chemical structures are used in the textile industries for dyeing purposes. Based on their chemical structures in terms of chromop-hore groups, dyes can be classified as azo dyes, anthraqui-none dyes, and reactive dyes and so on. Azo dyes are the most abundant group of dyes used in the textile industries. The main characteristics of these dyes are the presence of one or more azo (N=N) bonds and bonds between aromatic rings.3'4 Certain characteristics of dyes such as toxicity, resistance to degradation and photodegradation rates are believed to be dependent on the chemical structure of each dye.4 5 For example, Giwa et al,6 investigated the photodegradation of Reactive Yellow 81 and Reactive Violet 1 in aqueous solution with TiO2-P25 (Degussa) and observed that structural variation between the dyes molecules may have influenced their degradation rates. With regards to aromatic compounds, the number, position and the electronic nature of the substituents determine the efficiency of the photocatalytic degradation process.7 In their studies to determine the structural effect on photocatalytic degradation of substituted phenols through the use of TiO2 na-noparticles, Parra et al,8 observed that photoreactivity of substituted phenol depend on the electronic nature of the substitutes and their positions in the aromatic ring. The photocatalytic degradation process is more effective with greater electronic density on the aromatic ring.8 Therefore, it necessary to design technologies capable of photode- Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380-391_ 381 grading these dyes with their structural differences in mind. There has recently been considerable interest in the use of semiconductor photocatalysts for degradation of dyes in wastewater. There has been several reports on the use of TiO2 to degrade organic compounds in wastewater,910 due to its numerous advantages including high optical, electronic and photocatalytic properties, chemical stability, non-toxicity and low cost.11 In spite of these advantages, the practical application of TiO2 as an efficient photocatalyst for complete photodegradation of organic pollutants in wastewater is hampered by some inherent problems associated with TiO2 as a photocatalyst. These problems include its relatively high band gap of 3.2 eV which limits its ability to work in the visible light range, and its sensitivity to recombination of photogenerated electrons and hole, which decrease its photocatalytic acti-vity.12 In order to enhance the photocatalytic activity of TiO2, its band gap must be reduced, and the recombination rate of the photogenerated electrons and holes minimized. Lots ofeffort has been made into achieving these goals through various modification techniques. One common and most effective method to minimize the electron-hole recombination rate, and extend the absorption edge of TiO2 from the ultraviolet to visible light region is by doping TiO2 with transition metal cations.13,14 Out of many transition metals, iron has been regarded as a suitable dopant. Fe3+ has a radius of 0.69 A which is very similar to that of Ti4+ (0.75 A). This makes it easier for Fe3+ to be easily incorporated into TiO2 lattice. Furthermore, Fe3+ has the potential for trapping photogenerated electrons and holes since the energy level of Fe2+/Fe3+ lies close to that of Ti3+/ Ti4+.15 This subsequently results in improved separation of electron-hole pairs leading to improvement in quantum yield.16 Extensive studies have also been undertaken to improve the efficiency of TiO2 as a photocatalyst through the use of nonmetal dopants such as nitrogen,17 carbon,18 sulphur19 and fluorine.20 Band gap narrowing has been reported in C, S, and N doped TiO2,2122 with C-doped TiO2 exhibiting the best band gap narrowing ability.23 When doped together in TiO2, the combined effect of charge separation ability of Fe3+ and band gap narrowing potential of C and S is envisaged to result in modified TiO2 with excellent optical and photocatalytic properties. This work therefore involved the synthesis of pristine TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying weight percent of Fe3+ (0.3%, 0.6% and 1.0%) through the sol-gel method of preparation. The photoca-talytic degradation potential of these catalysts was assessed by their degradation of a monoazo dye (methyl orange) and diazo dye (congo red) as a function of time in aqueous solution under simulated visible light. The degradation of these two dyes by the catalysts were compared with regards to their structural differences. The influence of factors such as catalyst modification, pH and visible light intensity on the photocatalytic degradation of the dyes, as well as the degree of mineralization of the dyes was also studied using the catalyst with the best photodegradation potential. 2. Experimental 2. 1. Chemicals and Reagents Thiourea (CS(NH2)2), 99% was procured from Hopkin and Williams Ltd., England. Iron (III) chloride hexahydrate (FeCl3.6H2O), 99% was purchased from Merck, South Africa.The two azo dyes, Congo red and Methyl orange, absolute ethanol and titanium (IV) iso-propoxideTi (OC3H7)4, 97% were purchased from Sigma Aldrich, Germany.All chemicals used in this work were of analytical grade and were used without any further purification. Double distilled water was used throughout the experiment. The dye standard solutions were prepared by dissolving the appropriate masses of both congo red and methyl orange in 1000 mL. The standard solutions were then diluted to obtain the desired 20 ppm solution of each dye. The structures of the two azo dyes are shown in Figure 1. 2. 2. Synthesis of Fe3+/C/S-doped TiO2 Titanium (IV) isopropoxide (12.5 mL) was added to 50 mL absolute ethanol, followed by the dropwise addition of 1 mL polyethylene glycol. The mixture was stirred for 30 min. Calculated amounts of iron (III) chloride he-xahydrate representing Ti: Fe ratios of 0.3%, 0.6% and 1.0% were dissolved in 2 mL deionized water and added to the mixture. The mixture was stirred for another 1 h. Methyl orange Figure 1. Structure of methyl orange and congo red Anku et al.: Comparative Photocatalytic Degradation of Monoazo 382 Acta Chim. Slov. 2016, 63, 380-391 Thereafter, 3. 0 g of thiourea, which served as the source of C and S, was dissolved in 10 mL deionized water and added to the mixture slowly with further stirring for another 2 h. Finally, the mixture was dried in an oven at 100 °C for 12 h and calcined at 500 °C for 3 h. The pristine TiO2 and C/S-TiO2 were also synthesized following the same procedure but without the addition of both iron (III) chloride hexahydrate and thiourea (in the case of TiO2), and iron (III) chloride hexahydrate (for C/S-TiO2). 2. 3. Characterizations The X-ray diffraction (XRD) pattern was recorded on Philips PANalytical X'pert PRO X-ray diffractometer operating at 40kV using Cu-Ka radiation (X = 0.1541 nm). The measurement was performed over a diffraction angle range of 28 = 10°-100°. Fourier transform infrared (FTIR) spectroscopy for the nanocomposites was recorded on PerkinEl-mer spectrometer (Spectrum 100) in the wavelength range of 400 to 4000 cm1. The FTIR study was performed by using potassium bromide (KBr) pellet. Scanning electron microscopy (SEM) images were taken with a TESCAN (Vega 3 XMU) instrument. The elemental composition was studied using energy dispersed x-ray (EDX) attached to SEM. Transmission electron microscopy (TEM) images were taken using the TEM microscope (JEOL, JEM-2100F) with a working voltage of 120kV. Investigation of the optical absorption properties was carried out using a UV-Vis spectrophotometer (Shimadzu UV-2450). Barium sulphate (BaSO4) was used as the reflectance standard. 2. 4. Photodegradation Studies of the dye Solutions The photocatalytic degradation ability of the as synthesized nanoparticles on the two dye solutions was determined by measuring the absorbance of the dye solutions before and after their photodegradation, and the determination of the total organic carbon (TOC) of the dyes solutions before and after their degradation. The simulated visible light intensity was varied using Oriel PV reference cell system model 9115 V to produce a beam power equivalent to 0.5 sun, 0.7 sun, 1.0 sun and 1.3 sun intensities. This was achieved by setting the distance between the solar simulator (equipped with 150W ozone free xenon lamp) and the experimental set up to distances of 15 cm, 13 cm, 10 cm and 0.7 cm respectively. The pHs of the solutions were varied by adding 2M HCl and 2M NaOH solutions and monitored using Orion Per Hect pH meter. A Teledyne Tekmar TOC fusion meter, USA, was used for the total organic carbon analysis. 2. 5. Evaluation of Photocatalytic Activity The photocatalytic activities of the as-synthesized pristine TiO2, C/S-TiO2 and Fe3+/C/S-TiO2 were probed by their application in the degradation of 20 ppm aqueous solutions of methyl orange and congo red under simulated visible light. In this experiment, 20 mL (20 ppm) solution of each dye was placed in seven 50 mL beakers labelled 0-6. The photocatalysts (0.02 g) were mixed with each of the 7 dye solutions and the mixtures stirred magnetically in the dark for 30 min to establish adsorption equilibrium between the dyes and the catalysts. As a control, the beakers labelled zero (0) were removed after the 30 min stirring without visible light illumination. Then, 5 mL aliquot of this solution was withdrawn using disposable syringes fitted with 0.45 pm PVDF membranes. The remaining solutions labelled 1-6 were then illuminated using a Newport solar simulator, port 9600 full spectrum equipped with 150W ozone free xenon lamp, and fitted with a dichroic UV filter with a wavelength of 420 nm. The illumination was carried out for 180 min. The visible light illuminated solutions were chronologically removed from 1-6 after every 30 min interval and 5 mL aliquot of each was taken. The degradation was performed at the solution pH and 1 sun intensity. The concentrations of the dyes in the withdrawn solution after illumination (5 mL) were determined using Shimadzu UV-2450 spectrophotometer at wavelengths of 497 nm and 462 nm for congo red and methyl orange respectively. The same procedure was followed for the degradation experiments at pHs 3, 7, 9 and 12, and visible light intensities of 0.7 sun, 1.0 sun and 1.3 sun. 3. Results and Discussions 3. 1. FTIR Analysis The FTIR spectra of the as-synthesized undoped Ti-O2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying contents of Fe3+ are presented in Figure 2. In all the spectra, the strong and broad band below 1000 cm1 is assigned to the combined bands of Ti-O-Ti, Fe-O-Ti, S-O-Ti and O-Ti-C crystal vibrations,24 and the absorption bands at 1628 cm-1 and around 3500 cm-1 are due to -OH bending and stretching vibrations respectively as a result of absorbed water molecules. For the C/S-doped Ti-O2 and Fe3+/C/S-doped TiO2 photocatalysts (Figure 2b, 2c, 2d and 2e), the peak located at 1065 cm-1 may be attributed to bidentate sulphate ions (SO42-) co-ordinated to metal ions such as t4+.25 In addition, the peak at 1130 cm-1 can be ascribed to the S=O stretching vibration.26 The small peak at 2048 cm-1 may be a consequence of an out-of-phase stretching band of -N=C=O.27 The spectra for Fe3+/C/S-doped TiO2 (with varying Fe content) is similar to that of C/S-doped TiO2 but with changes in relative intensities and peak positions with increasing Fe content. The intensities of the absorption bands for Fe3+/C/S-do-ped TiO2 (0.3% Fe3+), (Figure 2c), are comparatively higher than those of the other nanocomposites. This observation is a possible confirmation that the Ti4+ is perfectly substituted by Fe3+ at this concentration. Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380-391 383 Figure 2. FT-IR spectra of pristine TiO2, C/S-TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe^+. 3. 2. Powder XRD Analysis The powder X-Ray diffraction patterns of undoped TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 are shown in Figure 3. All the diffractions are peaks characteristic of Anatase crystalline phase of TiO2. These peaks occur at 29 values of 25.3o, 37.9o, 48.1o, 53.9o, 55.0o, 62.9o, 68.9o, 70.4o, 75.8o and correspond to diffraction planes of 101, 004, 200, 105, 211, 204, 116, 200 and 215 respectively. This diffraction pattern is comparable to JCPDS no_ 21-1272. No Fe containing crystalline phase was observed in the XRD pattern. For a coordinated number of 6, Fe3+ and Ti4+ have similar ionic radii of 0.65 A and 0.75 Arespectively. Fe3+ can therefore easily substitute Ti4+ in the TiO2 lattice.28 The result of this analysis therefore means that there was a uniform substitution of Ti4+ with Fe3+ dopant. It is also evident that the catalysts are small in size due to the broad nature of the peaks. Crystallite sizes of catalysts were calculated using the Debye-Scherrer's equation:29 (1) where, D is the crystallite size, K is a shape factor with a value of 0.9, X is the wavelength of the X-ray (0.1541 nm), ¡3 is the value of full width at half maximum (FWHM) in the radiation of (101) plane in 26 scale, and 9 is the Bragg's diffraction angle at the maximum. The crystallite sizes were found to be 23.0 nm, 19.4 nm, 15.7 nm, 12.3 nm and 7.2 nm for TiO2, C/S-doped TiO2, Fe3+/C/S-doped TiO2(0.3% Fe3+), Fe3+/C/S-doped TiO2 (0.6% Fe3+) and Fe3+/C/S-doped TiO2 (1.0% Fe3+) respectively. It is evident that doping led to a decrease in the crystallite size of TiO2 and the size decreased consistently with increasing Fe3+ content. This decreased particle size may result in well-defined nanocrystalline powders with high surface area.30 Figure 3 XRD patterns of pristine TiO2, C/S-TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe3+. 3. 3. Brunauer-Emmett-Teller (BET) Surface Area Analysis The surface area analysis was intended to provide specific surface area assessment of the nanoparticles. Nitrogen adsorption-desorption isotherm was used to establish the effect of Fe doping on the BET surface, pore volumes and pore sizes of the nanoparticles. The results of the BET surface area, pore volume, and pore size analysis are presented in Table 1. The result shows that the nanocom-posites exhibited increased surface area with decreased crystallite size. Thus the undoped TiO2 had the least surface area of 32.7 m2/g while the Fe3+/C/S-doped TiO2 (0.3% Fe3+) had the largest specific surface area of 74.6 m2/g. Larger surface area can result in improved photocatalytic Anku et al.: Comparative Photocatalytic Degradation of Monoazo ... 384 Acta Chim. Slov. 2016, 63, 380-391 Table 1 Surface area, pore volume, pore size, indirect band gap, and percent degradation based on catalyst doping at solution pH and visible light irradiation with 1 sun intensity Sample Surface area (m2/g) Pore volume (cmg-1) Pore size (nm) Indirect band gap (eV) % Degradation Methyl Orange Congo Red TiO2 32.7 0.137 3.825 3.20 32.5 15.2 C/S-TiO2 32.5 0.180 3.794 2.42 69.4 61.9 Fe3+/C/S-TiO2 (0.3% Fe3+ ) 74.3 0.212 3.775 2.00 93.5 87.9 Fe3+/C/S-TiO2 (0.6% Fe3+ ) 56.1 0.224 3.719 2.14 90.7 83.0 Fe3+/C/S-TiO2 (1.0% Fe3+ ) 44.6 0.233 3.667 2.26 86.4 80.0 property as a result of availability of more active surface sites for improved adsorption of dye molecules.31 In addition, the pore volumes increase while the pore sizes decrease with increasing Fe concentration. Thus doping Ti-O2 with Fe ensured nanoparticles with larger surface area and pore volumes, and reduced pore sizes. 3. 4. SEM, TEM and EDX Analysis The surface morphology, microstructure and elemental compositions of the as-synthesized nanoparticles were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dis- Figure 4 (a) SEM image TiO2 (b) SEM image C/S-TiO2 (c) SEM image of Fe3+/C/S-doped TiO2 (1.0% Fe3+) (d) TEM image of TiO2 (e) TEM image of C/S-TiO2 (f) TEM image of Fe3+/C/S-doped TiO2 (1.0% Fe3+) and (g) EDX spectrum of Fe3+/C/S-doped TiO2 (1.0% Fe3+) Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380-391 385 persive X-ray (EDX) respectively. The SEM images of Ti-O2, C/S-TiO2, Fe3+/C/S-doped TiO2 (1.0% Fe3+) (Figure 4a, 4b and 4c) respectively, and the TEM images of TiO2, C/S-TiO2 and Fe3+/C/S-TiO2 (1.0% Fe3+) (Figure 4d, 4e and 4f) respectively revealed the crystalline and small-sized nature of the catalysts with distinct boundaries. Some aggregation of the nanoparticles was however observed. The EDX spectrum of Fe3+/C/S-doped TiO2 (1.0% Fe3+) nano-particle is shown in (Figure 4g). The EDX spectrum confirmed Ti, O, Fe, C and S as the components of the synthesized catalyst. The result shows strong peaks for Ti, O, and C. 3. 5. UV-Vis Analysis The UV-Vis absorption spectra of pure TiO2, C/S-TiO2 and Fe3+/C/S-TiO2 with varying wt% of Fe3+ is displayed in Figure 5. A significant red shift in the absorption spectrum of the pure TiO2 with the introduction of Fe, C and S can be observed. The absorption edge of the pure TiO2 occurred below 400 nm, meaning that its light absorption is limited only to the UV light range. However, the absorption edge significantly shifted to around 500 nm with the addition of the dopants. This is an indication that doping of pure TiO2 with C, S, and Fe improved its visible light absorption ability. This occurrence can be explained in terms of quantum confinement effect. It is observable that Fe3+/C/S-TiO2 (0.3% Fe3+), (Figure 5c) showed the highest absorption in the visible light region. The characteristic absorption band around 300 nm is a phenome- 035- 030- 0.25- 0.20- 3 a 0.15- ZJ v c 0.10- s J2 O an 0.05- — < 0.00- 41.05- -010- a (a)TiO; {b)C/S-H0, (t) F^'/C/S-TiO; (0.3% Fe^' ) 1/1 e 11 id) FeJ7C/S-TiO_, (0.6% F^" ) (e) Fe^'/C/S-TiO; (1.0% Fe^' ) —■—i—<— —i-'-1-1-1-'-1-1- 200 300 4(1(1 500 600 700 MOO Wavelength (nm) Figure 5. UV-Vis spectra of TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe3+. non attributed to inter band (valence and conduction band) and excitonic transition.27 3. 6. Band Gap Analysis The band gap values of the photocatalysts were obtained from a plot of Kubelka-Munk function through the Figure 6 Tauc plot for pure TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe3+. Anku et al.: Comparative Photocatalytic Degradation of Monoazo ... 386 Acta Chim. Slov. 2016, 63, 380-391 use of reflectance data. The Kubelka-Munk function is given in equation 4 below: Where, the reflectance (R) = Rsample/Rreference. The TauC plots for the pure and modified TiO2 which were obtained by plotting Tauc function (S(F(R)*hiCn against photo energy (hi) with n = 2, are depicted in Figure 6. The band gap values of the various catalysts are presented in Table 1. According to the results, the Fe3+/C/S-TiO2 (0.3% Fe3+) has the smallest band gap value of 2.00 eV while pure Ti-O2 has the highest value of 3.20 eV. This observation clearly verifies that doping of TiO2 with Fe/C and S successfully reduced its band gap. The band gap values decrease in the following order: Fe3+/C/S-TiO2 (0.3% Fe3+) < Fe3+/C/S-TiO2 (0.6% Fe3+) < Fe3+/C/S-TiO2 (1.0% Fe3+) < C/S-TiO2 < TiO2. Band gap narrowing can allow more absorption of visible light, and narrower band gap leads to more visible light absorption.32,33 It is however important to note that after the 0.3% Fe3+ dopant concentration the band gap values increase consistently with an increase in Fe3+ concentration. Such observation has been attributed to the steady movement of the conduction band of TiO2 above the first excited state of the dopant ion due to the increased dopant concentration. The dopant ions at the first excited state interact with the conduction band electrons of TiO2 causing higher energy transfer from the TiO2 to the metal dopant ions34 In addition, increase in band gap value with increased dopant concentration could be ascribed to increase in n-type carrier concentration as the absorption edge shifts to higher energy level.35 3. 7. Photodegradation Analysis According to Harikumar et al.36 it is necessary to understand the reaction rate and the manner in which the rate is affected by different factors in in order to design an optimized photodegradation system. Photocatalytic degradation process depends on many factors such as such as pH, light intensity, type of catalyst, oxygen concentration, concentration of the pollutant and the presence of inorganic ions. In this study, the degradation efficiencies of the dyes were studied based on catalyst type (effect of doping), light intensity and pH. 3. 7. 1. Effect of Doping The photodegradation ability of the as-synthesized photocatalysts (TiO2, C/S-TiO2, Fe3+/C/S-TiO2 (0.3% Fe3+), Fe3+/C/S-TiO2 (0.6% Fe3+) and Fe3+/C/S-TiO2 (1.0% Fe3+) was tested by applying them in the degradation of 20 mL (20 ppm) solution of methyl orange (mo-noazo dye) and congo red (diazo dye) with 0.02g of each catalyst. This experiment was carried out under simulated visible light intensity of 1 sun for 180 min. In addition, the degradation experiment was performed using bare TiO2 in the absence of UV filter. This was intended to find out the influence of UV filter on photocatalytic performance of TiO2. Bank experiment (without catalyst) was also performed. The result for methyl orange degradation is shown in Figure 7 (A) while that of congo red is presented in Figure 7 (B). It is apparent that the photodegradation efficiency of all the catalysts against both methyl orange and congo red exhibited the same trend where Fe3+/C/S-TiO2 (0.3% Fe3+) exhibited the best degradation efficiency against both dyes while TiO2 displayed the least degradation efficiency for both dyes. The rest of the catalysts degraded both dyes in the following order: C/S-TiO2 < Fe3+/C/S-TiO2 (1.0% Fe3+) < Fe3+/C/S-TiO2 (0.6% Fe3+). Compared to the use of UV filter, the bare TiO2 demonstrated higher photocatalytic degradation efficiency against both dyes in the absence of UV filter. This means that, though not to an appreciable extent, the unmodified TiO2 is relatively efficient in the UV range compared to the visible light range. However, the presence of the dopants extent it's activity to the visible light range, resulting in higher degradation efficiency of the modified TiO2 samples. The bank test indicated that photolysis of both dyes was very slow. The percentage degradation of both dyes by each catalyst is presented in Table 1. The enhanced photocatalytic activity of Fe3+/C/S-TiO2 (0.3% Fe3+) compared to other catalysts can be attributed to its improved visible light absorption (Figure 5), larger surface area, and reduced bad gap (Table 1). These factors possibly resulted in improved utilization of visible light instead of UV light, charge carrier transfer efficiency, enhanced adsorption of dye molecules and subsequent photodegradation due to large surface area and retardation of electron-hole recombination emanating from acceptance of electrons from the conduction band by the dopant ions. It is obvious, by comparing Figure 7 (A and B); that the monoazo dye was degraded faster than the diazo dye. All the catalysts demonstrated higher photodegradation of the monoazo dye compared to the diazo dye. For example, the best photocatalyst, Fe3+/C/S-TiO2 (0.3% Fe3+), degraded about 93% of methyl orange within 180 min (Figure 7A) while about 87% of congo red was degraded by the same catalyst within the same time frame (Figure 7B). This difference in photodegradation efficiency of the two azo dyes can be ascribed to structural differences. According to Figure 1, methyl orange contains one azo bond and one sulphonic group while congo red contain two azo bonds and two sulphonic groups. Meanwhile, the degradation of azo dyes is initiated by the electrophilic cleavage of its chromophoric azo bond (-N=N-) attached to the naphthalene ring.37 Thus the more azo bonds there are in the structure of the dye the longer time it will take to degrade the dye. In addition, azo dyes colour removal and degradation rates have been observed to be proportional to the number of azo and sulphonic groups present in their Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380-391 387 molecules.9 It can therefore be proposed that there exist a direct relationship between the dyes degradation efficiency and the number of azo bonds and sulphonic groups available in the dye molecules. In order to confirm the proposition that degradation efficiencies of the dyes were influenced by the azo bonds and sulphonic groups present in their molecules, photo-catalytic degradation of a 20 mL (20 ppm) triazo dye (Direct blue 71) was further performed using 0.02 g of Fe3+/C/S-TiO2 (0.3% Fe3+ ) for 180 min. This compound has three azo bonds and four sulphonic groups. The result (Figure 8) show that the dye experienced 62.8% degradation efficiency. Compared to the degradation efficiencies of methyl orange (93.5%) and Congo red (87.9%), direct blue 71 was degraded at a comparatively lower rate. This observation confirms the proposed direct relationship between the dyes degradation efficiency and the number of azo bonds and sulphonic groups available in dye molecules. 60- 50- 0 20 40 60 80 1 IK) 120 140 160 180 200 Time (min) Figure 8. Degradation efficiency of direct blue 71 by of Fe3+/C/S-TiO2 (0.3% Fe3+ Pseudo-first-order kinetics (Eqn 5) was used to determine the rate of degradation of the dyes by the various catalysts. where Co is the initial concentration, Ct is the time t and k is the rate constant. The results are presented in Figure 9 (A and B) for methyl orange and Congo red degradation rates respectively. The result show that the two dyes were degraded at different rates by all the catalysts. Fe3+/C/S-TiO2 (0.3% Fe3+ (the best photocatalyst) degraded both methyl orange and Congo red at faster rates of 16.28 x 10-3 and 15.33 x 10-3 while the bare TiO2 degraded both dyes at the lowest rates of 2.66 x 10-3 and 1.80 x 10-3 respectively. Comparatively, methyl orange experienced faster rate of degradation than Congo red. Because of its higher photocatalytic degradation efficiency against the two azo dyes, Fe3+/C/S-TiO2 (0.3% Fe3+) was the catalyst used to study the effects of light intensity and pH on the degradation efficiency of azo dyes. In addition, because methyl orange was degraded faster, it was chosen as a representative azo dye to study the effect of light intensity and pH on photodegradation of azo dyes. a) 120- * TiO, mitlul UVfilla-) Ti(l,(v.i[li IVfilial OS-TiO, Ft3+«S-T10,(&3%R;>fi ^ fiSTrCl, (().«« K/V 0 2(1 -10 60 80 100 120 140 160 ISO 200 Tinr(irin) b) KywMUV litter)-*- 11(^|™iKilUV litter) - ISank CSTO, ■ A- R^OSTOj(fty/ofc34) Rs^fOS-TiQ, (1 MTe3^) 0 20 40 60 Ml 1(10 120 140 160 ISO 200 Tine (ttiii) Figure 7. Effect of catalyst doping on degradation efficiency of (A) methyl orange and (B) Congo red by TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe3+. Anku et al.: Comparative Photocatalytic Degradation of Monoazo ... 388 Acta Chim. Slov. 2016, 63, 380-391 b) 15- ■ TiQj • CWiO, T ft /GS-TiQ,-0.6%Fe ffe^OS-TiCt,-1 m R: ■ ,, r-| -r r T-| -r T -r T t ., , -r .,. t—r I) 20 40 60 «I 100 120 140 160 ISO 2(H) Irradiation time (nin) a) ! 15 2.0- y L5 y = to 05- oo- ■ tiq, * FeîliDS-TiCyUHR?t T l^iUVIiCli-O«-;^ < ft^itJS-TiOj-l.Wtft A À63MÔ nin ' ïlHMO"3 nin ' / X ▼ -3 11.(0x1(1 I / XÀ -3 -, 6^0x10 nin ■ -3 -I 1««10 nin —I-,--1-,-1 i—|-r—i-r—i-1-r—i-i—i-r 0 20 40 60 NO 100 120 140 160 ISO 200 I rnirfhrtioti tine (nin) Figure 9. Kinetics of (A) methyl orange degradation and (B) Congo red degradation by TiO2, C/S-doped TiO2 and Fe3+/C/S-doped TiO2 with varying concentrations of Fe3+ under visible light irradiation. 3. 7. 2. Effect of pH One of the major factors that affect the degradation of pollutants by semiconductor photocatalyst is the solution pH since the catalyst surface charge and isoelectric point depend on pH. In addition, the solution pH is also a factor that determines the charge on the dye molecule. The study of the effect of pH on the photocatalytic degradation of organic pollutant is therefore an important consideration. In this study, the effect of pH on azo dye degradation was performed in the range of 2 to 12 with 0.02g of Fe3+/C/S-TiO2 (0.3% Fe3+) photocatalyst dispersed in 20 mL (20 ppm) solution of methyl orange. The results are displayed in Figure 10. The result showed that the photo- degradation efficiency of methyl orange decreased consistently with increasing pH from pH 2 to 12. There are many factors that determine the effect of pH on dye pho-tocatalytic degradation process, amongst which is the acid-base property of the photocatalyst which can be explained in terms of zero point charge,38 and the fact that the ionization state of the dye molecule depends on the solution pH. TiO2 has a zero point charge (pH pzc) at pH 6.8. This means that at pH < 6.8 (acidic medium) the surface of TiO2 becomes positively charged, and negatively charged in alkaline medium (pH > 6.8).36,39 On the other hand, due to its sulfonic group (SO3), methyl organge is negatively charged in solution. Hence there exist electrostatic force of attraction between the positively charged TiO2 surface and the negatively charged sulfonic groups of methyl orange in acidic medium. Consequently, the dye molecules were strongly adsorbed onto the TiO2 surface resulting in efficient degradation of the dye in acidic medium. In the alkaline medium however, both the TiO2 surface and the dye molecules are negatively charged resulting in electrostatic repulsion of the dye molecules. This caused the dye molecules to be sparingly adsorbed on the TiO2 surface resulting in diminished degradation efficiency of the dye in alkaline medium. The result therefore indicates that the degradation efficiency of the dye depends on the amount of dye molecule adsorbed onto the TiO2 surface. Figure 10. Effect of pH on degradation efficiency of methyl orange by Fe^/C/S-doped TiO2 (0.3% Fe3+) nanoparticle. 3. 7. 3. Effect of Light Intensity Photodegradation of methyl orange solutions under varied visible light intensities, 0.5 sun, 0.7 sun, 1.0 sun and 1.3 sun intensities, was performed to determine the influence of light intensity on the degradation efficiencies of the dye. Oriel PV reference cell system, model 91150 V, was used to measure the irradiance of the simulated sun. This experiment was performed with the same catalyst Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380-391_ 339 and dye solution specifications of 0.02 g catalyst suspended in 20 mL (20 ppm) solutions within an irradiation time of 180 min. Figure 11 represents the outcome of this analysis. There was a direct relationship between visible light intensity and degradation efficiency of the dye with respect to 0.5 sun, 0.7 sun and 1.0 sun. There was minimal degradation of the dye at 0.5 sun and 0.7 sun intensity while higher degradation was observed at 1.0 sun intensity to the point that about 93% of the dye was degraded within 120 min. Meanwhile, about 36% and 55% of the dye were degraded within the same 120 min at 0.5 sun and 0.7 sun intensities respectively. This occurrence may be related to the increase in light intensity resulting in an increase of the number of photons that reach the surface of the catalyst. As a result, the number of exited catalyst molecules increase causing an increase in the number of hy- Figure 11. Effect of light intensity on degradation efficiency of methyl orange by Fe3+/C/S-doped TiO2 (0.3% Fe3+) nanoparticle. droxyl and superoxide radicals responsible for the photodegradation process. On the other hand, an increase in light intensity to 1.3 sun did not result in any significant corresponding increase in the degradation efficiency. This probably means that the optimum number of photons required for an effective photocatalytic degradation was attained at 1.0 sun. Therefore, an increase in photon number at 1.3 sun did not produce any major change in the degradation efficiency. 3. 7. 4. Total Organic Carbon Analysis Total organic carbon (TOC) analysis was performed in order to determine the extent of mineralization of the methyl orange attained during the photodegradation process. This analysis is necessary because the disappearance of dye colour alone cannot be used as a measure to determine complete mineralization of the dye. Furthermore, the photodegradation process can result in the formation of colourless dye intermediates resulting in the disappearance of colour but may actually be more toxic than the dye itself. The analysis was done on the sample irradiated with 1 sun intensity with Fe3+/C/S-TiO2 (0.3% Fe3+) nanoparticle. The result of this analysis (Figure 12) revealed that the colour disappearance of the dye was faster than the degree of mineralization. The highest TOC removal was around 65%. The quick disappearance of colour could arise from the cleavage of the azo bond while the high TOC value may be due to difficulty in converting the N atom of the dye into oxidized nitrogen compounds since the hydroxyl radicals are short-lived and aliphatic chain interaction with hydroxyl radicals is minimal.40 This could mean that the dye molecules were converted to other intermediate forms which still exist in the solution irrespective of the dye decolourization, and signifies that degradation of the dye beyond 180 min may lead to complete mineralization. M 12 3 4 Irradiation tinr (hr) Figure 12. Percent TOC removal by Fe3+/C/S-TiO2 (0.3% Fe3+) nanoparticle. 4. Conclusion The visible light active hetero-elements doped TiO2 was successfully synthesized through sol-gel method, confirmed by FTIR, XRD, EDX AND UV-Vis analyses. Fe3+/C/S-TiO2 (0.3% Fe3+) was observed to be the best photocatalyst for the degradation of the azo dyes. The enhanced photocatalytic activity of Fe3+/C/S-TiO2 (0.3% Anku et al.: Comparative Photocatalytic Degradation of Monoazo 390 Acta Chim. Slov. 2016, 63, 380-391 Fe3+) compared to other catalysts can be attributed to its improved visible light absorption, larger surface area, and reduced bad gap. These factors possibly resulted in improved utilization of visible light, enhanced charge carrier transfer efficiency, greater adsorption of dye molecules and subsequent effective photodegradation of the dye. The monoazo dye experienced higher degradation efficiency over the diazo dye. The fast photodegradation of the mo-noazo dye compared to the diazo dye indicates that the number of azo bonds and sulphonic groups present in the azo dyes determined their photodegradation rate. The result of pH analysis showed that the photodegradation efficiency of methyl orange decreased consistently with increasing pH from 2 to 12 indicating that the degradation efficiency of the dye depend on the amount of dye molecule adsorbed on the TiO2 surface. There was a direct relationship between visible light intensity and degradation efficiency of the dye. TOC analysis revealed incomplete mineralization of the dye molecules within 180 min irrespective of the dye decolourization thus signifying that degradation of the dye beyond 180 min may lead to complete mineralization. 5. Reference 1. B. Manu, S. Chaudhari, Bioresour. Technol. 2002, 82, 225231. http://dx.doi.org/10.1016/S0960-8524(01)00190-0 2. N. D. Lourengo, J. M. Novais, H. M. Pinheiro, Environ technol. 2003, 24, 679-686. http://dx.doi.org/10.1080/09593330309385603 3. H. Zollinger. Color chemistry - Synthesis, properties, and applications of organic dyes and pigments, Willey-VCH: New York, 2003, pp. 219-243. 4. M. C. Costa, F. S. B. Mota, A. B. D. Santos, G. L. F. Men-donga, R. F. D. Nascimento, Quím. Nova, 2012, 35, 482486. http://dx.doi.org/10.1590/S0100-40422012000300008 5. Y. H. Lee, S. G. Pavlostathis, Water Res. 2004, 38, 18381852. http://dx.doi.org/10.1016Zj.watres.2003.12.028 6. A. Giwa, P. O. Nkeonye, K. A. Bello, E. G. Kolawole, A. O. Campos, Int. J. App, 2012, 2. 7. S. Parra, J. Olivero, C. Pulgarin, Appl. Catal. Part B: Environ. 2002, 36, 75-85. http://dx.doi.org/10.1016/S0926-3373(01)00283-1 8. S. Parra, J. Olivero, L. Pacheco, C. Pulgarin. Catal. Part B: Environ. 2003 43, 293-301. 9. S. A. Abo-Farha, J.Am. Sci, 2010, 6, 130-142. 10. U. G. Akpan, B. H. Hameed, J. Hazard. Mater, 2009,170, 520-529. http://dx.doi.org/10.1016/jjhazmat.2009.05.039 11. X. Zhang, Y. Wang, G. Li, J Mol. Catal A-Chem. 2005, 237, 199-205. http://dx.doi.org/10.1016/j.molcata.2005.03.043 12. B. Tryba, Int. J. Photoenergy, 2008, 2008. 13. C. Adán, A. Bahamonde, M. Fernández-García, A. Martínez-Arias, Appl. Catal B: Environ. 2007, 72, 11-17. http://dx.doi.org/10.1016/j.apcatb.2006.09.018 14. A. K. Ghosh, H. P. Maruska, J. Electrochem. Soc. 1977, 124, 1516-1522. http://dx.doi.org/10.1149/L2133104 15. W. Choi, A. Termin, M. R. Hoffmann, J. Phys. Chem, 1994, 98, 13669-13679. http://dx.doi.org/10.1021/j100102a038 16. N. Riaz, B. K. Mohamad Azmi, A. M. Shariff, Adv. Mat. Res. 2014, 925, 689-693. http://dx.doi.org/10.4028/www.scientific.net/AMR.925.689 17. R. Y. O. J. I. Asahi, T. A. K. E. S. H. I.Morikawa, T. Ohwaki, K. Aoki, Y. Taga, Science, 2001, 293, 269-271. http://dx.doi.org/10.1126/science.1061051 18. S. Sakthivel, H. Kisch, Angew. Chem. Int. Ed. 2003, 42, 4908-4911. http://dx.doi.org/10.1002/anie.200351577 19. T. Umebayashi, T. Yamaki, H. Itoh, K. Asai, Appl. Phys. Lett. 2002, 81, 454-456. http://dx.doi.org/10.1063/L1493647 20. J. C. Yu, J. Yu, W. Ho, Z. Jiang, L. Zhang, Chem. Mater. 2002, 14, 3808-3816. http://dx.doi.org/10.1021/cm020027c 21. D. E. De Vos, M. Dams, B. F. Sels, P. A. Jacobs, Chem Rev, 2002, 102, 3615-3640. http://dx.doi.org/10.1021/cr010368u 22. E. Barborini, A. M. Conti, I. Kholmanov, P. Piseri, A. Po-desta, P. Milani, M. Sancrotti, Adv. Mater, 2005, 17, 18421846. http://dx.doi.org/10.1002/adma.200401169 23. J. C. Yu, W. Ho, J. Yu, H. Yip, P. K. Wong, J. Zhao, Environ. Sci. Technol, 2005, 39, 1175-1179. http://dx.doi.org/10.1021/es035374h 24. V. Etacheri, M. K. Seery, S. J. Hinder, S. C. Pillai, Chem. Mater, 2010, 22, 3843-3853. http://dx.doi.org/10.1021/cm903260f 25. F. Wei, L. Ni, P. Cui, J. Hazard. Mater. 2008, 156, 135-140. http://dx.doi.org/10.1016/jjhazmat.2007.12.018 26. B. Liang, L Andrews, J. Phys. Chem A, 2002, 106, 69456951. http://dx.doi.org/10.1021/jp025915+ 27. L. Ren, X. Huang, F. Sun, X. He, Mater lett, 2007, 61, 427-431. http://dx.doi.org/10.1016Zj.matlet.2006.04.097 28. J. Zhu, W. Zheng, B. He, J. Zhang, M. Anpo, J. Mol. Catal A: Chem. 2004, 216, 35-43. http://dx.doi.org/10.1016/j.molcata.2004.01.008 29. A. K. Singh, U. T. Nakate, Sci. World J. 2014, 2014. 30. J. Moon, H. Takagi, Y. Fujishiro, M. Awano, J. Mater. Sci. 2001, 36, 949-955. http://dx.doi.org/10.1023/A:1004819706292 31. J. Moon, H. Takagi, Y. Fujishiro, M. Awano, J. Mater. Sci, 2001, 36, 949-955. http://dx.doi.org/10.1023/A:1004819706292 32. M. Xing, X. Li, J. Zhang. Sci. Rep. 2014, 4, 1-7. 33. K. Maeda, K. Domen. J. Phys. Chem. Lett. 2010, 1, 26552661. http://dx.doi.org/10.1021/jz1007966 34. S. Kumar, Z. Jindal, N. Kumari, N. K. Verma. J Nanopart. Res. 2011, 13, 5465-5471. http://dx.doi.org/10.1007/s11051-011-0534-5 35. S. A. Yousaf, S. Ali. Coden. Jnsmac. 2008, 48, 43-50. 36. P. S. Harikumar, L. Joseph, A. Dhanya, J. Environ. Eng. Ecol. Sci. 2013, 2, 2. http://dx.doi.org/10.7243/2050-1323-2-2 37. M. Muruganandham, M. Swaminathan, Dyes Pigm. 2004, 62, 269-275. http://dx.doi.org/10.1016/j.dyepig.2003.12.006 Anku et al.: Comparative Photocatalytic Degradation of Monoazo Acta Chim. Slov. 2016, 63, 380- 391 391 38. H. R. Pouretedal, M. Hosseini, Acta Chim. Slov, 2010, 57, 415-423. 39. N. Wang, J. Li, L. Zhu, Y. Dong, H. Tang, H. J. Photochem. Photobiol A: Chem. 2008, 198, 282-287. 40. I. K. Konstantinou, T. A. Albanis, Appl. Catal. B: Environ. 2004, 49, 1-14. http://dx.doi.org/10.1016/j.apcatb.2003.11.010 http://dx.doi.org/10.1016/j.jphotochem.2008.03.021 Povzetek Tekom raziskav smo preučevali fotokatalitičen razpad monoazo (metiloranž) in diazo (kongo rdeče) barvil v vodnih raztopinah nanokompozitov Fe3+/C/S dopiranega TiO2. Nanokompozite smo sintetizirali s sol-gel metodo in karakterizira-li z naslednjimi tehnikami: XRD, FTIR, SEM, TEM, EDX, BET in UV-Vis. Fotokatalitični razpad barvil smo spremljali pod simulirano vidno svetlobo, uporabili pa smo TiO2, C/S dopiran TiO2 in Fe3+/C/S dopiran TiO2 z različnimi koncentracijami ionov Fe3+. Preučevali smo vpliv katalizatorja, pH-ja raztopine in intenzitete svetlobe. V primeru Fe3+/C/S dopiranega TiO2 smo opazili zmanjšano vrednost energijske špranje (band gap) in izboljšano aktivnost vidne svetlobe. Glede na fotokatalitično učinkovitost lahko preučevane materiale zapišemo v naslednjem vrstnem redu: TiO2 < C/S/ dopiran TiO2 < Fe3+/C/S dopiran TiO2. Fe3+/C/S dopiran TiO2 (0.3% Fe3+) je izkazoval najboljše fotokatalitične lastnosti. V primeru monoazo barvila smo opazili višjo stopnjo razpada kot v primeru diazu barvila. Razpad azo barvil se je zmanjšal s povečanjem pH vrednosti od 2 do 12. Zvišanje intenzitete vidne svetlobe je povečalo učinkovitost razpada barvil pod vplivom svetlobe. Opazili smo, da se je barvilo hitreje razbarvalo, kot pa mineraliziralo. Anku et al.: Comparative Photocatalytic Degradation of Monoazo ... 392 Acta Chim. Slov. 2016, 63, 392-398 DOI: 10.17344/acsi.2016.2431 Scientific paper A 2:2:2 Complex of Vanadium(V) with 4-(2-Thiazolylazo)orcinol and 2,3,5-Triphenyl-2#-Tetrazolium Chloride Kiril Blazhev Gavazov,* Vassil Borisov Delchev, Kremena Tomova Mileva, Teodora Stefcheva Stefanova and Galya Kostadinova Toncheva Faculty of Chemistry, University of Plovdiv "Paissii Hilendarski", 4000, Plovdiv, Bulgaria * Corresponding author: E-mail: kgavazov@abv.bg Tel.:+35932261425 Received: 15-03-2016 Abstract Abstract. The complex formation in the vanadium(V) / 4-(2-thiazolylazo)orcinol (TAO) / 2,3,5-triphenyl-2H-tetrazo-lium chloride (TTC) liquid-liquid extraction-chromogenic system was studied. The chloroform-extracted complex has a composition of 2:2:2 under the optimum conditions (pH 4.8-5.2, extraction time 3 min, concentration of TAO 3.4 x 10-4 mol dm-3, and concentration of TTC 9.4 x 10-4 mol dm-3) and could be regarded as a dimer (D) of two 1:1:1 species (S) presented by the formula (TT+)[VO2(TAO)]. The constant of extraction was calculated by two methods and some analytical characteristics were determined. The wavelength of maximum absorption (A ), molar absorptivity (£A) and fraction extracted (E) were found to be A = 545 nm, £545 = 1.97 x 104 dm3 mol-1 cm-1, and E = 97.9 %. The ground-state equilibrium geometries of the complexes S and D were optimized by quantum chemical Hartree-Fock calculations using 3-21G* basis functions. The bonding and interaction energies were calculated as well. Keywords: liquid-liquid extraction; spectrophotometry; tetrazolium salt; 5-methyl-4-(2-thiazolylazo)resorcinol; 2:2:2 complex; HF calculations. 1. Introduction Vanadium is a trace element with many industrial applications.1 The recent interest in this element is also related to the observed beneficial role of its compounds for different aspects of human health.2-4 Complexes with various reagents have been proposed for determination of vanadium.5-7 However, the concentration of its species in environmental and biological samples is often lower than the corresponding limits of determination. A classical approach to solve this problem and improve the method's characteristics is to combine the instrumental method (e.g. spectrophotometry) with liquid-liquid extraction (LLE) - a simple technique for separation and preconcentration which does not require expensive equipment.8 Among the complexes applied for vanadium LLE-spectrophotometric determination and speciation of particular interest are these with participation of azocom-pounds (AC) and tetrazolium cations (TZ+).5,6,9,10 The fol- lowing ACs were investigated as components of ternary V(V)-AC-TZ complexes: 4-(2-pyridylazo)resorcinol10-12, 4-(2-thiazolylazo)resorcinol,13,14 and 4-(2-thiazolyla-zo)orcinol (TAO).15 The obtained results show that the V(V):AC molar ratio in these complexes differs,11-15 as a rule, from the typical 1:1 ratio established in the presence of other ion-association reagents (Table S1). However, the reason for this peculiarity is unclear and quantum-chemical calculations on V-AC-TZ ternary complexes have never been conducted. In the light of this, the purpose of the current work is experimental (LLE-spectrophotometric) and theoretical (calculations at the HF/3-21G* level) study on the complexes formed between V(V), 2,3,5-triphenyl-2H-te-trazolium chloride (TTC) and TAO. Scarce information about the binary V(V)-TAO complex in water-ethanol medium has been provided by Shalamova.16 TTC was selected for the present study because of its high application potential17-20 and recent interest to its ion-associa- tes.21-26 Gavazov et al.: A 2:2:2 Complex of Vanadium(V) Acta Chim. Slov. 2016, 63, 392-398 393 2. Experimental 2. 1. Reagents and Apparatus • NH4VO3 (puriss. p.a., VEB Laborchemie Apolda) dissolved in doubly distilled water, 2 x 10-4 mol dm-3. • TAO (95%, Sigma-Aldrich Chemie GmbH) dissolved in slightly alkalized (KOH) distilled water, 3 x 10-3 mol dm-3. • TTC (p.a., Loba Feinchemie GMBH), 4.7 x 10-3 mol dm-3 aqueous solutions. • Ethanol (96%). • Chloroform (p.a.), additionally distilled. • Acetate buffer solution prepared from 2 mol dm-3 aqueous solutions of CH3COOH and NH4OH. The resulting pH was checked by Hl-83140 pH meter. • A Camspec M508 spectrophotometer (United Kingdom), equipped with 10 mm path-length cells. 2. 2. Procedure for Establishing the Optimum LLE-Spectrophotometric Conditions Aliquots of V(V) solution (1 cm3), TAO solution, buffer solution (2 cm3) and TTC solution were pipetted into 100 cm3 separatory funnels. The resulting solutions were diluted with distilled water to a total volume of 10 cm3. Then 10 cm3 of chloroform were added. The funnels were closed with stoppers and shaken for extraction. After separation of the layers, portions of the organic extracts were transferred through filter papers into cells. The absor-bances were read against respective blank samples. re A1 and A3 are the absorbances (measured against blanks), obtained after a single and triple extractions, respectively. The single extraction and the first stage of the triple extraction were performed with 10 cm3 of chloroform under the optimum extraction-spectrophotometric conditions (Table 1). The organic layers were transferred into 25 cm3 calibrated flasks and the flask for the single extraction was brought to volume with chloroform. The second stage of the triple extraction was performed by adding a 7 cm3 portion of chloroform to the aqueous phase, which remained after the first stage. The third stage was performed in the same manner. The two successive organic layers were transferred to the flask containing the organic layer obtained after the first stage. The volume was brought to the mark with chloroform and shaken for homogenization.15,27,28 3. Theoretical The ground-state equilibrium geometries of the single and dimeric complexes were optimized at the HF level using 3-21G* basis functions. Their vibration spectra were calculated in order to check for imaginary frequencies (no such vibrational eigenvalues were calculated). The stability of the complexes S and D was evaluated by the bonding and interaction energies found by the equations 1 and 2:29-31 ¿Eh = Ess (1) 2. 3. Procedure for Determining the Complex Composition in Water-ethanol Medium 1 cm3 of V(V) solution, i cm3 of TAO solution (i varies from 0.2 to 4 cm3), 2 cm3 of buffer solution (pH 5.4) and 3 cm3 of ethanol were added into test tubes with ground stoppers. The volumes were made up to 10 cm3 with distilled water. Then the tubes were closed and shaken for homogenization. Portions of the obtained solutions were transferred into cells. The absorbances were read against respective blank samples. 2. 4. Procedure for Determining the Distribution Coefficients The distribution coefficients D = Xc(V(V)org)/ Xc(V(V)) were found from the ratio D = A1/(A3-A1), whe- AE = ESS-^E?P (2) where ESS is the energy of the given complex, whereas E; and ESi P are the energies of the fragments found with 'ghost' orbitals and single-point calculations respectively with geometries as obtained by the optimizations. Thus, the basis-set superposition error (BSSE) was estimated by the equation 3: BSSE =£(^-4) (3) The theoretical calculations were performed with the GAUSSIAN 03 program package. The results were visualized with the ChemCraft program. Table 1. Extraction-spectrophotometric optimization of the V(V)-TAO-TTC-water-chloroform system Parameter Optimization range Optimal value Figure Wavelength, nm Visible range 545 Fig. 1 pH of the aqueous phase 3.7-6.7 4.8-5.2 Fig. 2 Extraction time, min 0.25-6 3 Fig. S1 Concentration of TAO, mol dm-3 (0.15-6.0) x 10-4 3.4 x 10-4 Fig. 3 Concentration of TTC, mol dm-3 (0.24-14.1) x 10-4 9.4 x 10-4 Fig. 3 Gavazov et al.: A 2:2:2 Complex of Vanadium(V) 394 Acta Chim. Slov. 2016, 63, 392-398 4. Results and Discussion 4. 1. Optimum LLE-spectrophotometric Conditions Absorption spectrum of the chloroform-extracted ternary complex is shown in Figure 1. The maximum is at X = 545 nm. It is shifted to 5 nm as compared to the maximum of the binary V(V)-TAO complex in water-ethanol medium (X = 550 nm)16 and practically coincides with that of other complexes of the type V(V)-TAO-TZ in chloroform studied in our previous paper.15 It should be mentioned that the position of this maximum is constant independently of changes in pH and concentrations of the reagents. The optimum LLE-spectrophotometric conditions are given in Table 1. The optimization experiments included varying the pH (Figure 2), time of the extraction, and concentration of the reagents (Figure 3). The concentration of V(V) in the aque- Figure 3. Absorbance of extracted complex vs concentration of the reagents (R): 1. R = TAO, c = 2 X 10-5 mol dm-3, c___= 9.4 X 10-4 mol dm-3, pH 5.0, X = 5S nm; 2. R = TTC, c mol dm-3, c = 4.0 x 10-4 mol dm-3, pH 5.1, X = 545^ T=C2 x 10-5 nm Figure 1. Absorption spectra of the ternary complex (curve 1) and blank (curve 2) in chloroform. c x 10-4 mol dm-3, c -- 2 x 10 mol dm-3, c 9.4 x 10W)nol dm-3, pH 5.0. = 4.2 ous phase was kept constant during the experiments (2 x 10-5 mol dm-3); the temperature was ca. 22 °C. 4. 2. Composition, Formula and Equation The molar ratios of the components of the ternary complex, TAO:V(V) and TTC:V(V), were determined by the mobile equilibrium method (Figure 4) which is applicable for compounds of the type AnBm, where n = m (n > 1).32 The slopes a ± SD of the obtained straight lines for n = m = 2 (Figure 4) are close to 2:1.95 ± 0.05 (straight line 1; R = TAO) and 1.96 ± 0.09 (straight line 2; R = TTC). At the same time, the corresponding slopes for n = m = 1 {1.21 ± 0.05 (R = TAO) and 1.20 ± 0.04 (R = TTC)} and n = m = 3 {2.69 ± 0.10 (R = TAO) and 2.72 ± 0.15 (R = TTC)} are far from 1 and 3. The TTC:V(V) molar ratio was determined by an independent method33 based on the effect of dilution on the 0 i-1-1-1 ■ i- 3.7 4.2 4.7 5.2 5.7 6.2 6.7 PH Figure 2. Absorbance of the complex (curve 1) and blank (curve 2) in chloroform vs pH of aqueous phase. c = 2 X 10-5 mol dm-3, c = 4.0 X 10-4 mol dm-3, c = 8.0 X 1(Fmol dm-3, X = 545 nm. TAO TTC -0.5 -I-r-*-,-.-----i-,- ■6 -5 -1 -3 -2 -1 0 Log c'R, mol dm 3 Figure 4. Determination of R-to-V(V) molar ratios by the mobile equilibrium method. The data are derived from the experimental points shown in Fig. 3. Straight line equations: (1) y = 1.95* + 9.75 (R = TAO, r2 = 0.9974); (2) y = 1.96* + 8.98 (R = TTC, r2 = 0.9824) Gavazov et al.: A 2:2:2 Complex of Vanadium(V) Acta Chim. Slov. 2016, 63, 392-398 395 degree of dissociation. The experimental points (Figure 5) determine a straight line for TTC:V(V) = 2:2 (y = -3433x + 2587; r2 = 0.9978) and a curve for TTC:V(V) = 1:1. Therefore, the results of both methods agree well. They show that the complex has a composition of 2:2:2. Its formation and extraction can be represented with equation 4, which is consistent with the state of V(V)7 and TAO34 at the working conditions (pHopt and c ). We believe that V(V) does not change its oxidation sta^auring the complex formation.9-15 2H2VO4-(aq) + 2H2TAO(aq) + 2 TT^ ^ (TT+)2[VO2(TAO)]2 (o) + 4H2O(aq) (4) Figure 5. A straight line (1; molar ratio of 2:2, left ordinate) and a curve (2; molar ratio of 1:1, right ordinate) obtained by the dilution method. c = c , c = 3.4 X 10-4 mol dm-3, pH 5.2, X = 545 nm V(V) TTC TAO r 4. 3. Constant of Extraction and Fraction Extracted sar-Boltz method35 (Figure 6), extended by the equation 5, proposed in our previous paper15 for this kind of complexes. Kex = 0.0625 x (4/k)3 x ym x (1-y )- l v J max7 (5) The corresponding values agree very well: Log Kex = 13.47 ± 0.02 and Log Kex = 13.53 ± 0.05. The fraction extracted was calculated by the formula E% = 100 x D /(D +1), were D is the distribution coefficient foP theVoptimum extraction conditions. The following value was obtained: E = (97.9 ± 0.1)%. D was found by comparison of the absorbance values v(v) obtained after single and triple extractions: DVW = 46 ± 2 (4 replicate experiments). 4. 4. Analytical Characteristics The dependence between the concentration of V(V) and the absorbance of the extracted complex was studied under the optimum conditions (Table 1). A very good linearity was obtained in the concentration range of 0.2-4.6 |g cm-3 (r2 = 0.9998, N = 8) (Figure S2). The linear regression equation was A = 0.399 y- 0.0076, where A is the absorbance and y is the concentration of V(V) (|g cm-3). The standard deviations of the slope and intercept were 0.002 and 0.005, respectively. The limits of detection (LOD) and quantitation (LOQ), calculated as 3 and 10 times standard deviation of the intercept divided by the slope, were LOD = 0.04 |g cm-3 and LOQ = 0.14 |g cm-3. The molar absorptivity (e) and Sandell's sensitivity (SS) were e^ = 1.97 x 104 dm3 mol1 cm-1 and SS545 = 2.6 x 545 10-3 cm-2, respectively. The constant of extraction was calculated by two methods: the dilution method33 (Figure 5) and the Likus- Figure 6. Determination of the constant of extraction (K ) by the Likussar-Boltz method at k = c +c = 1 X 10-4mol dm-3. c = o . , , , 3 tt ^ „ V(V) TAO TTC 9.4 X 10-4 mol dm-3, pH 5.2. 4. 5. Composition of the Binary V-TAO Complex in Water-ethanol Medium Shalamova16 provides the following scarce information about the binary V(V)-TAO complex in water-ethanol medium: pHopt = 5.0-5.5, Amax = 540 nm, and emax = 1.3 x 104 dm3 mol-1 cm-1. There is no information about the composition of the complex. In order to fill this gap we used the method of As-mus36 (Figure S3) and the mobile equilibrium method32 (Figure S4). The results show that the molar ratio between the reacting TAO and V(V) is 1:1 (not 2:2). 4. 6. Optimized Ground-state Equilibrium Geometries The ternary complex has a composition of 2:2:2 and can be regarded as obtained by dimerization of two 1:1:1 (V:PAR:TT) single complexes (see Table S1 and Refs. S10-S18). Single complexes. The optimized ground-state equilibrium geometries of two possible single complexes S1 Gavazov et al.: A 2:2:2 Complex of Vanadium(V) 396 Acta Chim. Slov. 2016, 63, 392-398 and S2 are illustrated in Figure 7. For the optimization of the first structure (S1) we started from a T-shaped structure between the anionic and cationic parts, [VO2(TAO)]-and TT+, respectively. The tetrazolium ring was initially located over the deprotonated O(8) atom. The T-shape was changed during the fully-relaxed optimization but the close distance between O(8) and the tetrazolium ring was kept: e.g. the distance O(8)-N(28) = 3.501 A. Two close interactions are observed between the fragments 1 and 2 in the complex S1. They are two weak H-bonds between the benzene ring hydrogens and the oxygen atoms of the fragment 1: H(64)-O(7) = 2.460 A and H(63)-O(18) = 2.189 A. These bonds cause a interring twist between the tetrazolium and benzene residues: 2a(I)) 2219 2679 Rint 0.028 0.026 Data/restraints/parameters 2472/0/176 3088/6/228 R[F2 > 2o(F2)] 0.087 0.056 wR(F2 ) 0.168 0.184 GooF = S 1.06 1.10 Ap /Ap (e À3) rmax rmin 1 1 / 0.77 and -0.64 e À-3 1.20 and -0.82 e À-3 Slyvka et al.: Two Related Copper(I) n-Complexes Based Acta Chim. Slov. 2016, 63, 399-401 405 2. 2. 1 Preparation of [Cu(2-apyt)NO3] (1) To 4.5 mL of ethanol/benzene solution (3.6 mL of C2H5OH and 0.9 mL of C6H6) of Cu(NO3)2 ■ 3H2O (0.90 mmol, 0.217 g) 0.170 g (0.91 mmol) of 1-apyt/2-apyt mixture was added dropwise with stirring. The prepared suspension was placed into a 5 mL test-tube and then copper-wire electrodes in cork were inserted. By the application of alternating-current tension (frequency 50 Hz) of 0.48 V for 15 days a very small amount of colorless crystals of 1 appeared on copper electrodes. non-hydrogen atoms were refined using an anisotropic model; the only exception is Cu2B (with s.o.f. 10%) atomic displacement in 1 that was refined in the isotropic mode. Hydrogen atoms were placed in ideal positions and refined as riding atoms with relative isotropic displacement parameters. The crystal data parameters, data collection and the refinement details are summarized in Table 1. 3. Results and Discussion 2. 2. 2 Preparation of [Cu(2-apyt)(H2O)](BF4) (2) To 4.5 mL of ethanol/benzene solution (3.2 mL of C2H5OH and 1.3 mL of C6H6) of Cu(BF4)26H2O (0.90 mmol, 0.311 g) 0.170 g (0.91 mmol) of 1-apyt/2-apyt mixture was added dropwise with stirring. The prepared light-blue suspension immediately was prone to the alternating-current reduction (frequency 50 Hz) of 0.43 V. After 16 days a few suitable for single X-ray studying crystals of 2 were found on the electrode surface. 2. 4. Single Crystal X-ray Diffraction Studies The collected diffraction data for 1 and 2 were processed with the Rigaku CrystalClear software suite program package.19 The structures were solved by direct methods using SHELXS-97 and refined by least squares method on F2 by SHELXL-2014 with the following graphical user interfaces of OLEX2.20,21 Metal atom in 1 is split into two positions (s.o.f. 90% and 10%). Fluorine atoms of BF4- anion in 2 were refined over two disordered positions (s.o.f. 59% and 41%) applying the same geometry restraints for disordered units. Atomic displacements for The structures 1 and 2 demonstrate the first examples of N-allyltetrazoles allyl derivatives n-complexes with ionic copper(I) salts. In both compounds 2-apyt molecule acts as chelate-bridging n, o-ligand being attached to the metal center by C=C bond of allyl group, pyridyl N atom and the most nucleophilic N atom of tetrazole ring (Figs. 1 and 2). Copper(I) atom adopts distorted tetrahe-dral (t4 = 0.71 for 1, t4 = 0.67 for 2) surrounding (t4 -four-coordinate geometry index)22, including two mentioned N atoms of the same 2-apyt moiety, C=C bond of the neighbouring organic molecule and one O atom of the anion in 1 and water molecule in 2 (Table 2). Taking into account that the sum of van der Waals radii of Cu and O according to the recent results reported by Batsanov23 and Alvarez24 is much higher than Cu1A-O3 distance value of 2.918(5) A, copper(I) surrounding in 1 may be completed to five including one more O atom of the same nitrate anion. It is interesting to note that [Cu(2-apyt)NO3] (1) is to-pologically reminiscent {[Cu(1-abtr)NO3]}n n-complex with 1-allylbenzotriazole (1-abtr),25 in which 1-abtr molecule connects two Cu+ ions through p2-C3N4- bridge into an infinite {[Cu(1-abtr)]+}n chain, while the last ones are coupled by two bridging NO3- anions in the geminated chain. An additional coordination of pyridyl N atom to Figure 1. Centrosymmetric [Cu(2-apyt)NO3]2 dimer in 1 (a) and double {[Cu(1-abtr)NO3]2}n chain (è).25 (a) One of the disordered copper(I) positions with s.o.f. 10% in 1 is shown in semidashed mode. Symmetry codes: (i) 2 - x, -y, 1 - z. Slyvka et al.: Two Related Copper(I) n-Complexes Based 402 Acta Chim. Slov. 2016, 63, 399-405 Cu+ in 1 prevents the second nitrate ion binding to the metal, resulting in the finite macrocyclic [Cu(2-apyt)NO3]2 fragment with two five-membered {CuN2C2} rings (Fig. 1). Due to a coordination to Cu(I), pyridyl ring of the 2-apyt in the structure of complex 1 is tilted by nearly 5° with respect to tetrazole ring. Both the above angle value and the distance of 1.437(5) A for C5-C6 between carbon atoms of tetrazole and pyridyl rings indicate the noticeable contribution of n-component of the bond. Marked hardness of fluorine in BF4- anion is not conducive for its coordination to such "soft acid" as Cu+, therefore in 2 water O atom completes metal surrounding. In general, Cu+-F(BF4) contacts in the structures of substituted olefins n-complexes occur rarely and, in particu- Table 2. Selected bond distances and angles for complex 1 and 2. Distance (A) Angle (deg) 1 Cu1A-N4 2.071(5) N4-Cu1A-O1 100.6(2) Cu1A-O1 2.120(5) N4-Cu1A-N5 80.3(2) Cu1A-N5 2.072(6) N5-Cu1A-O1 93.0(2) Cu1A-m! 1.938(6) m-Cu1A-N4 134.6(2) Cu1B-m! 1.929(7) m-Cu1A-O1 113.0(2) C2-C1 1.349(10) m-Cu1A-N5 125.3(3) C5-C6 1.437(9) C1!-Cu1A-C2! 38.4(3) 2 Cu1-N4 2.021(3) N4-Cu1-O1 95.6(1) Cu1-N5 2.060(3) N4-Cu1-N5 81.8(1) Cu1-O1 2.236(3) N5-Cu1-O1 100.6(1) Cu1-m!! 1.921(4) m!!-Cu1-N4 139.1(1) C1-C2 1.360(5) m!!-Cu1-O1 105.1(1) C5-C6 1.462(4) m!!-Cu1-N5 126.8(1) Symmetry codes: (i) 2 - x, -y, 1 - z; (ii) 1.5 - x, -0.5 + y, 1.5 - z. m -middle point of C1=C2 double bond. lar, they were previously found in Cu(I) n-complexes with diallylsulfide,26 diallylamine or ethylene in co-presence of 3,6-bis(byridin-2-yl)-4,5-dihydropyridazine.27 28 Thus, Cu+ ions in 2 connect 2-apyt molecules in the infinite undulated {[Cu(2-apyt)(H2O)]+}n chain while tetrafluorobo-rate anion is bound with the metal center only through water bridge by O-H-F contacts (Table 3). As a result complex 2 is constructed in such a way, that BF4- becomes a specific H-bonded linker between two neighbouring {[Cu(2-apyt)(H2O)]+}n chains, binding them together into double chain. Pyridyl ring of the 2-apyt in complex 2 is tilted by 6° with respect to tetrazole ring. The presence of N-allylic group in 2-apyt with more "softer" C=C bond brings a considerable difficulties to neighbouring N atoms (possessing border line basicity) to be bound with "soft" Cu+ center. Instead, pyridyl N atom of 2-apyt in 1 and 2 becomes more favourable to compete with tetrazole moiety in metal coordination for two reasons: due to greater nucleophility of pyridyl N atom and due to a formation of a five-membered {Cu-N2C2} ring. It is well known, that chelate effect strongly increases complex stability. In comparison to 1 and 2, there are a number of Cu(II) complexes with 2-substitu-ted 5-(2-pyridyl)tetrazoles in which organic ligand, being attached to the metal center in the same way, produces similar five-membered rings.29,30 Most likely an appearance of {CuN2C2} ring is the main reason of selective com-plexation of 2-apyt from starting mixture of 1-apyt and 2-apyt under electrochemical condition to form thermody-namically stable 1 and 2 in crystalline form. Otherwise, the presence of three nitrogen atoms with decreasing nuc-leophilicity in the order N4>N3>N2 and possessing higher spatial accessibility in 1-apyt should promote a considerable increase of tetrazole moiety participation in metal coordination, thus significantly reducing the contribution of chelating {CuN2C2} function. Similar isomer-selective a) b) Figure 2. Coordination environment of copper (a) and H-bonded array (b) of double chain in 2. One of the two disordered positions of BF4 with s.o.f. 41% is shown in semidashed mode. Symmetry codes: (i) 1 - x, -y, 1 - z; (ii) 1.5 - x, -0.5 + y, 1.5 - z. Slyvka et al.: Two Related Copper(I) n-Complexes Based Acta Chim. Slov. 2016, 63, 399-403 405 Table 3. Geometry of selected hydrogen bonds in 1 and 2. Atoms involved Symmetry Distances, A Angle, deg D-H-A D-H H-A D-A D-H-A 1 C7-H7-O1 1 - x, -y, 1 - z 0.95 2.37 3.160(8) 140 C9-H9-O2 1 - x, -0.5 + y, 1.5 - z 0.95 2.40 3.280(10) 154 C10-H10-03 x, 0.5 - y, 0.5 + z 0.95 2.49 3.434(10) 179 2 O1-H1C-F2A 1 - x, -y, 1 - z 0.87 2.07 2.76(2) 137 O1-H1D-F1A 0.87 1.99 2.84(2) 166 O1-H1C-F2B 1 - x, -y, 1 - z 0.87 2.32 2.97(2) 132 O1-H1D-F1B 0.87 2.05 2.85(1) 152 C7-H7-F4A -0.5 + x, -0.5 - y, -0.5 + z 0.95 2.53 3.320(11) 141 a) Figure 3. Diverse crystal packing of 1 (a) and 2 (b) along [100] direction. b) a) H...0 (18.6%) 0.6 OS l.o 1.3 14 IK 2 0 2.2 14 b) H...H (21.8%) (A) 0.6 OS 1.0 IJ 1.4 1.6 I.S 20 2.2 2.4 c) Figure 4. Hirshfeld surface analysis of [Cu(2-apyt)NO3]2 dimer in 1 structure. (a) Hirshfeld surface mapped with dnorm which highlights both donor and acceptor ability. (b) Fingerprint plots of crystal fragments resolved into H-O contacts. (c) Fingerprint plots of crystal fragments resolved into H---H contacts. The full fingerprint appears beneath each decomposed plot in grey. complexation of copper(I) ionic salts towards 1- and 2-allylbenzotriazoles was described few years ago.31'32 The chelating effect of 2-allylbenzotriazole was found to be a crucial factor in the construction of the n-compounds with copper(I) tetrafluoroborate, perchlorate and hydrosulfate. One may compare [Ag2(1-apyt)2](ClO4)2 n-com- Slyvka et al.: Two Related Copper(I) n-Complexes Based 404 Acta Chim. Slov. 2G16, 63, 399-405 plex (prepared also from a mixture of 1-apyt and 2-apyt), in which 1-apyt molecule is attached to one silver(I) atom by means of C=C bond and pyridyl N atom, forming less stable eight-member {CuN2C5} ring, while two tetrazole N atoms are ^2-bonded to crystallographically another Ag(I) atoms.33 To analyze interactions between the particles the Hirshfeld surface was built for [Cu(2-apyt)NO3]2 dimer in 1. The most prominent C-H—O interactions between the dimers can be seen in the Hirshfeld surface plot as the red areas (Fig. 4). Fingerprint plots were produced to show the intermolecular surface bond distances with the regions highlighted for (C)H-O(N) and residual H-H interactions. The C—C contacts belong to n - n-interactions between heterocyclic nuclei and contribute only 3.6% to the surface area. The contribution to the surface area for H-H contacts is 21.8%. 4. Conclusion The synthesis and crystal structures of the two new n-compounds [Cu(2-apyt)NO3] (1) and [Cu(2-apyt)(H2O)](BF4) (2) with 2-allyl-5-(2-pyridyl)-2#-tetra-zole (2-apyt) have been performed. Due to significant li-gand chelating effect the isomer-selective complexation of 2-apyt with Cu+ under ac-electrochemical condition was found. The ligand 2-apyt acts in 1 and 2 as a chelate-bridging n,o-ligand, being attached to the Cu(I) by means of allylic C=C bond, by pyridyl N atom and one tetrazole N atom. In complex 1 a centrosymmetric [Cu(2-apyt)NO3]2 dimer is formed due to a bridging organic li-gand. Participation of H2O in metal coordination in 2 leads to linking of organometallic fragment into infinite {[Cu(2-apyt)(H2O)]+}n chain, interconnected by O-H-F hydrogen bonds among water and tetrafluoroborate anions into double chain. To depict interactions between the particles in 1 Hirshfeld surface analysis has been performed. 5. Supplementary Material CCDC number contains the supplementary crystal-lographic data for this paper. Copies of the data can be obtained free of charge on applications to the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: int. code +(1223)336-033; e-mail for inquiry: fileserv-@ ccdc.cam.ac.uk). 6. Acknowledgments We would like to acknowledge the financial support by Slovenian Research Agency (ARRS). 7. References 1. P. N. Gaponik, S. V. Voitekhovich, O. A. Ivashkevich, Russ. Chem. Rev. 2006, 75, 507-539. http://dx.doi.org/10.1070/RC2006v075n06ABEH003601 2. G. Aromi, L. A. Barrios, O. Roubeau, P. Gamez, Coord. Chem. Rev. 2011, 255, 485-546. http://dx.doi.org/10.1016Zj.ccr.2010.10.038 3. E. Lodyga-Chruscinska, Coord. Chem. Rev. 2011, 255, 1824-1833. http://dx.doi.org/10.1016/j.ccr.2011.02.023 4. Y. Hu, C.-Y. Li, X.-M. Wang, Y.-H. Yang, H.-L. Zhu., Chem. Rev. 2014, 114, 5572-5610. http://dx.doi.org/10.1021/cr400131u 5. G. Karabanovich, J. Roh, T. Smutny, J. Nemecek, P. Viche-rek, J. Stolarikovâ, M. Vejsovâ, I. Dufkovâ, K. Vâvrovâ, P. Pâvek, V. Klimesovâ, A. Hrabâlek, Eur. J. Med. Chem. 2014, 82, 324-340. http://dx.doi.org/10.1016/j.ejmech.2014.05.069 6. C. Elschenbroich, Organometallics (2006) Wiley-VCH: Weinheim. 7. F. H. Allen, Acta Cryst. B. 2002, B58, 380-388. http://dx.doi.org/10.1107/S0108768102003890 8. Y. Slyvka, E. Goreshnik, O. Pavlyuk, M. Mys'kiv, Cent. Eur. J. Chem. 2013, 11, 1875-1901. 9. Yu. Slyvka, N. Pokhodylo, R. Savka, E. Goreshnik, M. Mys'kiv, Chem. Met. Alloys 2009, 2, 130-137. 10. Yu. Slyvka, N. Pokhodylo, R. Savka, Z. Mazej, E. Goresh-nic, M.Mys'kiv, Chem. Met. Alloys 2010, 3, 201-207. 11. W. Wang, Acta Cryst. E. 2008, E.64, m900. 12. W. Wang, Acta Cryst. E. 2008, E.64, m930. 13. W. Wang, Acta Cryst. E. 2008, E.64, m759. 14. W. Wang, Acta Cryst. E. 2008, E.64, m902. 15. S. K. Wolff, D. J. Grimwood, J. J. McKinnon, M. J. Turner, D. Jayatilaka, M. A. Spackman, University of Western Australia, 2012. 16. M. A. Spackman, D. Jayatilaka, CrystEngComm 2009, 11, 19-32. http://dx.doi.org/10.1039/B818330A 17. N. T. Pokhodylo, O. Ya. Shiyka, V. S. Matiychuk, N. D. Obushak, Zh. Org. Khim. 2010, 46, 423. 18. B. M. Mykhalichko, M. G. Mys'kiv. Ukraine Patent UA 25450A, Bull. No 6, 1998. 19. Rigaku Corporation, The Woodlands, Texas, USA. (1999) CrystalClear. 20. G. M. Sheldrick. Acta Cryst. C. 2015, C71, 3-8. http://dx.doi.org/10.1107/S2053229614024218 21. O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H. Puschmann, J. Appl. Cryst. 2009, 42, 339- 341. http://dx.doi.org/10.1107/S0021889808042726 22. L. Yang, D. R. Powell, R. P. Houser, Dalton Trans. 2007, 955-964. http://dx.doi.org/10.1039/B617136B 23. S. S. Batsanov, Inorg. Mater. 2001, 37, 871-885. http://dx.doi.org/10.1023/A:1011625728803 24. S. Alvarez, Dalton Trans. 2013, 42, 8617-8636. http://dx.doi.org/10.1039/c3dt50599e 25. E. A. Goreshnik, M. G. Mys'kiv, Acta Chim. Slov. 2011, 58, 772-775. Slyvka et al.: Two Related Copper(I) n-Complexes Based Acta Chim. Slov. 2016, 63, 399-405 405 26. E. A. Goreshnik, D. Schollmayer, V. V. Olijnik, Russ. Coord. Chem. 1997, 23, 773-776. 27. E. A. Goreshnik, M. G. Mys'kiv, Yu. A. Simonov, M. D. Mazus, L. I. Budarin, Kristallographia 1992, 37, 100-103. 28. M. Maekawa, T. Miyazaki, K. Sugimoto, T. Okubo, T. Kuro-da-Sowa, M. Munakata, S. Kitagawa, Inorg. Chim. Acta. 2014, 410, 46-53. http://dx.doi.org/10.10167j.ica.2013.10.015 29. S. Mustafa, B. U. Rao, M. S. Surendrababu, K. K. Raju, G. N. Rao, Chem. Biodiver. 2015, 12, 1516-1534. http://dx.doi.org/10.1002/cbdv.201400369 30. A. P. Mosalkova, S. V. Voitekhovich, A. S. Lyakhov, L. S. Ivashkevich, J. Lach, B. Kersting, P. N. Gaponik, O. A. Ivashkevich, Dalton Trans. 2013, 42, 2985-2997. http://dx.doi.org/10.1039/C2DT32512H 31. E. A. Goreshnik, A. A. Vakulka, Yu. I. Slyvka, M. G. Mys'kiv, J. Organomet. Chem. 2012, 710, 1-5. http://dx.doi.org/10.1016/jjorganchem.2012.02.024 32. E. A. Goreshnik, Yu. I. Slyvka , M. G. Mys'kiv, Inorg. Chim. Acta 2011, 377, 177-180. http://dx.doi.org/10.1016Zj.ica.2011.08.008 33. Yu. I. Slyvka, N. T. Pokhodylo, E. A. Goreshnik, M. G. Mys'kiv, J. Struct. Chem. 2014, 55, 368-369. http://dx.doi.org/10.1134/S0022476614020279 Povzetek Dva nova bakrova(I) n-kompleksa [Cu(2-apyt)NO3] (1) in [Cu(2-apyt)(H2O)](BF4) (2) sta bila sintetizirana iz mešanice izomerov 1-alil-5-(2-piridil)-2.ff-tetrazola (1-apyt) in 2-alil-5-(2-piridil)-2.ff-tetrazola (2-apyt) ter ustreznih bakrovih soli z elektrokemijskim postopkom in sta bila strukturno okarakterizirana. Selektivno kompleksiranje omogoča tvorbo kompleksov, ki vsebujejo 2-apyt izomer. V obeh spojinah je bakrov kation koordiniran z C=C vezjo alilne skupine, dušikovem atomom piridilnega obroča ter dušikovem atomom tetrazolnega obroča. V obeh spojinah ima Cu+ center te-traedrično koordinacijsko sfero, ki vsebuje tudi kisikov atom NO3- aniona v 1 ter koordinirano molekulo vode v 2. Struktura 1 vsebuje [Cu(2-apyt)NO3]2 dimer. Prisotnost molekule vode v koordinacijskem okolju bakrovega iona v 2 omogoča tvorbo neskončnih {[Cu(2-apyt)(H2O)]2+}n verig. Interakcije med gradniki so bile proučevane s pomočjo Hirshfeldove analize. Slyvka et al.: Two Related Copper(I) n-Complexes Based 406 Acta Chim. Slov. 2016, 63, 406-410 DOI: 10.17344/acsi.2016.2520 Short communication Synthesis, Crystal Structure and Catalytic Property of a Cobalt(II) Compound Derived From 2-Bromo-W-(2-Hydroxy-5-Methylbenzylidene)Benzohydrazide Fu-Ming Wang Key Laboratory of Coordination Chemistry and Functional Materials in Universities of Shandong, Department of Chemistry, Dezhou University, Dezhou Shandong 253023, P. R. China * Corresponding author: E-mail: wfm99999@ 126.com Received: 18-04-2016 Abstract With a tridentate Schiff base ligand 2-bromo-N'-(2-hydroxy-5-methylbenzylidene)benzohydrazide (HL) and cobalt nitrate, a cobalt(II) compound [Co(L)2]NO3 • %H2O (1) was prepared and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. The compound crystallizes in the monoclinic space group P21/c. Single crystal X-ray diffraction analysis reveals that the Co atom is coordinated by the NOO donor atoms of the Schiff base li-gands, in an octahedral coordination. The compound show effective catalytic oxidation property on some olefins. In general, oxidation of the substrates gave the corresponding epoxides in over 80% yields for various styrene and 71% for cyclohexene. Keywords: Schiff base; Cobalt complex; Crystal structure; Catalytic property. 1. Introduction In recent years, the catalytic oxidation of olefins has aroused much attention in the production of chemicals and fine chemicals since epoxides are key starting materials for a wide variety of oily products.1 Because of the environment friendly nature H2O2 has been regarded as the first selected oxidant in the oxidation of olefins. Transition metal complexes with various ligands have presented interesting catalytic properties.2 Among the complexes, cobalt species show efficient catalytic oxidation pro-perties.3 Hydrazones are versatile ligands in coordination chemistry.4 Recently, we have reported the catalytic property of a molybdenum complex with hydrazone ligand.5 As an extension of the work on the exploration of new catalytic material, in this paper, a new cobalt(II) compound H L derived from the Schiff base ligand 2-bromo-N'-(2-hy-droxy-5-methylbenzylidene)benzohydrazide (HL) was prepared and its catalytic oxidation property was performed. 2. Experimental 2. 1. Materials and Methods 5-Methylsalicylaldehyde and 2-bromobenzohydra-zide were purchased from Alfa Aesar. Cobalt nitrate he-xahydrate and solvents are commercially available and were used without further purification. Elemental analyses for carbon, hydrogen, and nitrogen were carried out with an Elementar Vario EL. Infrared spectra were measured on KBr disks with a Hitachi I-5040 FT-IR spectropho-tometer. Molar conductivity was determined in methanol with a concentration of 10-3 M at room temperature on a DDS-11A conductometer. 2. 2. Synthesis of the Compound 5-Methylsalicylaldehyde (0.136 g, 1.00 mmol) and 2-bromobenzohydrazide (0.215 g, 1.00 mmol) were mixed and stirred in methanol (20 mL) for 30 min. Then, Wang et al.: Synthesis, Crystal Structure and Catalytic Property Acta Chim. Slov. 2016, 63, 406-410 407 cobalt nitrate hexahydrate (0.291 g, 1.00 mmol) dissolved in methanol (20 mL) was added, and stirred for another 30 min. The solution was kept still in air for a few days to slowly evaporate in order to give brown block-shaped single crystals of 1. Yield: 32%. Analysis: Found: C 45.27, H 3.13, N 8.97%. Calculated for C60H50Br4Co2N10O15: C 45.36, H 3.17, N 8.82%. IR (KB-r, cm-1): v(O-H), 3451; v(N-H), 3217; v(C=N), 1605; v(NO3), 1377 and 835. geometrically and refined with a riding model, with isotropic displacement coefficients U(H) = 1.2 U(C) or 1.5 U(Cmethyl). Br1 atom is disordered over two sites, with occupancies of 0.727 and 0.273 and Br2 atom is disordered over two sites, with occupancies of 0.534 and 0.466. Atoms C12, C13, C14, C15, Br4, N9, O9, 010 and O11 were restrained using ISOR instruction.. Crystallographic data are summarized in Table 1. Selected bond lengths and angles are listed in Table 2. 2. 3. Catalytic Oxidation Experiment Catalytic experiment was carried out in a 50 mL glass round-bottom flask fitted with a reflux condenser and placed in an oil bath at prearranged temperature under continuous stirring. The oxidation was carried out as follows: the compound 1 (0.032 mmol) was dissolved in 10 mL 1,2-dichloroethane. Then 10 mmol alkene was added to the reaction mixture and 30 mmol TBHP was added. The reaction mixture was refluxed for 1 h. The reaction products were monitored at periodic time intervals using gas chromatography. The oxidation products were identified by comparison with authentic samples (retention times in GC). 2. 4. X-Ray Structure Determination Data collection was performed with a Bruker Apex II CCD diffractometer at 298 K. The structure was solved by direct methods with SHELXS-97 and refined by full-matrix least squares (SHELXL-97) on F2.6 All non-hydrogens were refined anisotropically. Hydrogens were placed Table 2. Selected bond lengths (Â) and bond angles (deg) for 1 Co(1)-N(3 1.994(7) Co(1)-N(1 2.002(7) Co(1)-O(3 2.034(6) Co(1)-O(1 2.036(6) Co(1)-O(4 2.042(6) Co(1)-O(2 2.083(6) Co(2)-N(7 1.987(7) Co(2)-N(5) 2.011(7) Co(2)-O(5 2.029(6) Co(2)-O(7) 2.049(5) Co(2)-O(6) 2.068(6) Co(2)-O(8) 2.120(6) N(3)-Co(1) -N(1) 166.0(3) N(3)-Co(1) -O(3) 88.0(3) N(1)-Co(1 -O(3) 101.8(3) N(3)-Co(1) -O(1) 102.9(3) N(1)-Co(1 -O(1) 87.2(3) O(3)-Co(1 -O(1) 89.2(2) N(3)-Co(1) -O(4) 80.1(3) N(1)-Co(1 -O(4) 90.3(3) O(3)-Co(1) -O(4) 167.9(2) O(1)-Co(1 -O(4) 90.9(2) N(3)-Co(1) -O(2) 90.7(3) N(1)-Co(1 -O(2) 79.4(3) O(3)-Co(1) -O(2) 91.3(2) O(1)-Co(1 -O(2) 166.4(2) O(4)-Co(1) -O(2) 91.5(3) N(7)-Co(2) -N(5) 166.7(3) N(7)-Co(2) -O(5) 98.4(2) N(5)-Co(2) -O(5) 88.7(3) N(7)-Co(2) -O(7) 87.0(2) N(5)-Co(2) -O(7) 104.3(2) O(5)-Co(2) -O(7) 89.2(2) N(7)-Co(2) -O(6) 94.8(3) N(5)-Co(2) -O(6) 78.7(3) O(5)-Co(2) -O(6) 166.7(2) O(7)-Co(2) -O(6) 90.2(2) N(7)-Co(2) -O(8) 78.8(3) N(5)-Co(2) -O(8) 89.8(2) O(5)-Co(2) -O(8) 91.9(2) O(7)-Co(2) -O(8) 165.8(2) O(6)-Co(2) -O(8) 92.0(2) Table 1. Crystal data, data collection and structure refinement for 1 Molecular Formula Formula weight Crystal system Space group a (Ä) b (Ä) c (Ä) ß (deg) V (Ä3) Z Dc (g cm-3) F(000) ^ (mm-1) Measured reflections Unique reflection Observed reflections [I > 2a(I)\ R t int Parameters Restraints Final R index [I > 2o(I)\ R index (all data) Goodness-of-fit on F2 C60H50Br4Co2N10O15 1588.6 Monoclinic P21/c 13.406(1) 27.443(2) 18.142(2) 101.147(8) 6548.5(10) 4 1.611 3176 3.019 40016 11962 4969 0.1238 831 59 0.0793, 0.1678 0.2081, 0.2315 0.978 3. Results and Discussion 3. 1. Chemistry The compound 1 was prepared by the reaction of equimolar quantities of the Schiff base ligand with cobalt nitrate hexahydrate in methanol. Crystals of 1 are stable in air and soluble in methanol, ethanol, DMF and DMSO, but are insoluble in water. The molar conductance measured in methanol with a concentration of 10-3 M is 115 Q-1 cm2 mol-1, indicating the compound is a 1:1 electrolyte.7 3. 2. Infrared Spectra The compound has been characterized by infrared spectroscopy. The broad band centered at 3451 cm-1 is assigned to the O-H vibrations. The sharp band at 3217 cm-1 is assigned to the N-H vibration of the amino groups. The strong band indicative of the C=N group is observed at 1605 cm-1.8 The bands indicative of the nitrate anions are located at 1377 and 835 cm-1. Wang et al.: Synthesis, Crystal Structure and Catalytic Property 408 Acta Chim. Slov. 2016, 63, 406-410 3. 3. Crystal Structure Description of 1 The asymmetric unit of 1 contains two mononuclear cobalt(II) complex cations, two nitrate anions and one water molecule of crystallization. The Co(1) complex cation of the compound is shown in Figure 1. Since the geometries of both complex cations are very similar, the Co(2) complex cation of the compound is shown in Figure S1 as a supplementary material. The Co atoms are coordinated by two phenolate O, two imine N and two carbonyl O atoms from two Schiff base ligands, forming octahedral coordination. The distortion of the octahedral coordination can be observed from the cis and trans coordinate bond angles, viz. 79.4(3)-102.9(3)° and 166.0(3)-167.9(2)° for Co(1), 78.8(3)-104.3(2)° and 165.8(2)-166.7(3)° for Co(2). The bond lengths related to the Co atoms are similar to each other, and also comparable to those observed in cobalt complexes with Schiff base ligands.9 The dihedral angles between the two benzene rings of the Schiff base ligands C(1)-C(6) and C(10)-C(15), C(16)-C(21) and C(25)-C(30), C(31)-C(36) and C(40)-C(45), C(46)-C(51) and C(55)-C(60) are 105.4(5), 74.8(5), 35.9(5), and 62.4(5)°, respectively. Figure 1. The molecular structure of the Col complex cation with 30% probability thermal ellipsoids. In the crystal structure of 1, two adjacent complex cations are linked by O(7)-H(7D)-O(3) and O(1)-H(1A)-O(5) hydrogen bonds (Table 3), to form a di-mer. The dimers are further linked by nitrate anions through N(4)-H(4A)-O(13), O(15)-H(15B)-O(9), O(15)-H(15B) -O(11), N(8)-H(8A)-O(12), N(6)-H(6A) -O(15) and N(2)-H(2A)-O(10) hydrogen bonds (Table 3), to form chains, as shown in Figure 2. 3. 4. Catalytic Property The catalytic results are given in Table 3. As seen from the results, the products of the reactions are epoxi-des and the selectivities for these products are 100%. High TONs (turn over numbers = moles of substrate converted per mole of 1) obtained for the substrates suggest a very high catalytic efficiency for 1. In general, oxidation of the substrates gave the corresponding epo-xides in over 80% yields for various styrene and 71% for cyclohexene. The catalytic property of the compound is comparable to the oxidovanadium(V) complex.10 Figure 2. Molecular packing structure of 1, viewed along the a axis. Hydrogen bonds are shown as dashed lines. Table 3. Distances (Â) and angles (°) involving hydrogen bonding in 1 D-H-A d(D-H) d(H-A) d(D-A) Angle D-H-A) O(7)-H(7D)—O(3) 0.93 1.65 2.442(7) 141 O(1)-H(1A)—O(5) 0.93 1.63 2.463(7) 146 N(4)-H(4A)-O(13)i 0.86 2.00 2.85(1) 170 O(15)-H(15B)-O(9)U 0.85 2.38 3.20(2) 163 O(15)-H(15B)-O(11)U 0.85 2.23 2.88(1) 133 N(8)-H(8A)-O(12)U 0.86 1.96 2.79(1) 163 N(6)-H(6A)—O(15) 0.86 1.98 2.80(1) 159 N(2)-H(2A)—O(10) 0.86 1.94 2.78(1) 168 Symmetry codes: i: 1 + x, V - y, -V + z; ii: x, V - y, -V + z. Wang et al.: Synthesis, Crystal Structure and Catalytic Property Acta Chim. Slov. 2016, 63, 406-410 409 Table 3. Catalytic oxidation results3 Substrate Product Conversion (%)b TONc a The molar ratio of catalyst:substrate:TBHP is 1:300:1000. The reactions were performed in mixture of CH3OH/CH2Cl2 (V:V = 6:4; 1.5 mL). b The GC conversion (%) was measured relative to the starting substrate after 1 h. c TON: turn over number = moles of substrate converted per mole of 1. 4. Conclusions In summary, a new mononuclear cobalt(II) compound with a tridentate Schiff base ligand 2-bromo-N'-(2-hydroxy-5-methylbenzylidene)benzohydrazide has been prepared and characterized. Single crystal structure of the compound was determined. The Co atom in the complex cation is in an octahedral coordination. Single crystal of the compound is stabilized by hydrogen bonds. The compound show effective catalytic oxidation property on some olefins. In general, oxidation of the substrates gave the corresponding epoxides in over 80% yields for various styrene and 71% for cyclohexene. 5. Supplementary Material CCDC-1448088 contains the supplementary cry-stallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif. 6. Acknowledgments The Department of Chemistry of Dezhou University is acknowledged for financial support. 7. References 1. (a) S. Shit, D. Saha, D. Saha, T. N. G. Row, C. Rizzoli. Inorg. Chim. Acta 2014, 415, 103-110; http://dx.doi.Org/10.1016/j.ica.2014.02.036 (b) T. R. Amarante, P. Neves, A. C. Gomes, M. M. Nolasco, P. Ribeiro-Claro, A. C. Coelho, A. A. Valente, F. A. A. Paz, S. Smeets, L. B. McCusker, M. Pillinger, I. S. Goncalves. Inorg. Chem. 2014, 53, 2652-2665; http://dx.doi.org/10.1021/ic403033j (c) A. C. Gomes, S. M. Bruno, M. Abrantes, C. I. R. Magal-haes, I. S. Goncalves, A. A. Valente, M. Pillinger. J. Organo-met. Chem. 2014, 760, 205-211; http://dx.doi.org/10.1016/jjorganchem.2013.10.037 (d) B. Terfassa, J. A. Schachner, P. Traar, F. Belaj, N. C. M. Zanetti. Polyhedron 2014, 75, 141-145; http://dx.doi.org/10.1016Zj.poly.2014.03.024 (e) A. J. Musacchio, L. Q. Nguyen, G. H. Beard, R. R. Knowles. J. Am. Chem. Soc. 2014, 136, 12217-12220. http://dx.doi.org/10.1021/ja5056774 2. (a) F. Wang, C.-H. Lu, I. Willner. Chem. Rev. 2014, 114, 2881-2941; http://dx.doi.org/10.1021/cr400354z (b) L. M. D. R. S. Martins, A. J. L. Pombeiro. Coord. Chem. Rev. 2014, 265, 74-88; http://dx.doi.org/10.1016/jxcr.2014.01.013 (c) A. Quintard, J. Rodriguez. Angew. Chem. Int. Ed. 2014, 53, 4044-4055; http://dx.doi.org/10.1002/anie.201310788 (d) K. Riener, S. Haslinger, A. Raba, M. P. Hogerl, M. Coko-ja, W. A. Herrmann, F. E. Kuhn. Chem. Rev. 2014, 114, 5215-5272; http://dx.doi.org/10.1021/cr4006439 (e) M. Amini, M. M. Haghdoost, M. Bagherzadeh. Coord. Chem. Rev. 2014, 268, 83-100. http://dx.doi.org/10.1016/jxcr.2014.01.035 3. (a) Y. K. Zhao, J. Q. Lin, Y. D. Liu, B. C. Ma, Y. Ding, M. D. Chen. Chem. Commun. 2015, 51, 17309-17312; http://dx.doi.org/10.1039/C5CC07448G (b) M. Khorshidifard, H. A. Rudbari, B. Askari, M. Sahihi, M. R. Farsani, F. Jalilian, G. Bruno. Polyhedron 2015, 95, 1-13; http://dx.doi.org/10.1016/j.poly.2015.03.041 (c) K. Sarma, N. Devi, M. Kalita, B. Sarma, P. Barman. J. Coord. Chem. 2015, 68, 3685-3700; http://dx.doi.org/10.1080/00958972.2015.1075241 (d) T. Baskaran, R. Kumaravel, J. Christopher, S. Radha-krishnan, A. Sakthivel. Catal. Lett. 2015, 145, 851-859; http://dx.doi.org/10.1007/s10562-015-1492-9 (e) S. M. Islam, K. Ghosh, R. A. Molla, A. S. Roy, N. Salam, M. A. Iqubal. J. Organomet. Chem. 2014, 774, 61-69; http://dx.doi.org/10.1016/jjorganchem.2014.10.010 (f) T. Kurahashi, H. Fujii. Inorg. Chem. 2013, 52, 39083919. http://dx.doi.org/10.1021/ic302677f 4. (a) S.-S. Qian, X. Zhao, J. Wang, Z. You. Acta Chim. Slov. 2015, 62, 828-833; (b) R. Vafazadeh, M. Alinaghi, A. C. Willis, A. Benvidi. Acta Chim. Slov. 2014, 61, 121-125. 5. F. M. Wang. Russ. J. Coord. Chem. 2014, 40, 268-272. http://dx.doi.org/10.1134/S1070328414040101 6. G. M. Sheldrick. SHELXL-97, Program for the Refinement of Crystal Structures, Göttingen (Germany): University of Göttingen, 1997. 7. W. J. Geary. Coord. Chem. Rev. 1971, 7, 81-122. http://dx.doi.org/10.1016/S0010-8545(00)80009-0 Wang et al.: Synthesis, Crystal Structure and Catalytic Property 410 Acta Chim. Slov. 2016, 63, 406-410 8. R. Pagadala, P. Ali, J. S. Meshram. J. Coord. Chem. 2009, 62, 4009-4017. http://dx.doi.org/10.1080/00958970903208284 9. (a) C. Jing, C. Wang, K. Yan, K. Zhao, G. Sheng, D. Qu, F. Niu, H. Zhu, Z. You. Bioorg. Med. Chem. 2016, 24, 270276; http://dx.doi.org/10.1016/j.bmc.2015.12.013 (b) H. A. R. Pramanik, P. C. Paul, P. Mondal, C. R. Bhattac-harjee. J. Mol. Struct. 2015, 1100, 496-505; http://dx.doi.org/10.1016/j.molstruc.2015.07.076 (c) S. Roy, A. K. Maji, D. Sutradhar, S. Choubey, R. Ghosh, B. K. Ghosh. J. Indian Chem. Soc. 2015, 92, 1387-1393; (d) X.-M. Hu, L. W. Xue, G.-Q. Zhao, W. C. Yang. Russ. J. Coord. Chem. 2015, 41, 197-201; http://dx.doi.org/10.1134/S1070328415030045 (e) M. Ghosh, M. Layek, M. Fleck, R. Saha, D. Bandyo-padhyay. Polyhedron 2015, 85, 312-319. http://dx.doi.org/10.1016Zj.poly.2014.08.014 10. K.-H. Yang. Acta Chim. Slov. 2014, 61, 629-636. Povzetek Kobaltovo(II) spojino [Co(L)2]NO3 • 1H2O (1) smo pripravili iz trovezne Schiffove baze 2-bromo-W-(2-hidroksi-5-me-tilbenziliden)benzohidrazidom (HL) in kobaltovim nitratom ter jo okarakterizirali z elementno analizo, IR spektroskopijo in rentgensko strukturno analizo. Spojina kristalizira v monoklinski prostorski skupini P21/c. Monokristalna rentgenska difrakcija je razkrila, da je Co atom oktaedrično koordiniran z NOO donorskimi atomi Schiffove baze. Spojina ima učinkovite katalitične lastnosti za oksidacijo nekaterih olefinov. Na splošno, oksidacije substratov dajo ustrezne epokside z več kot 80% izkoristkom pri različnih stirenih in 71% pri cikloheksenu. Wang et al.: Synthesis, Crystal Structure and Catalytic Property DOI: 10.17344/acsi.2016.2361 Acta Chim. Slov. 2016, 63, 411-415 411 Short communication Introduction of Branching Degrees of Octane Isomers Anton Perdih Faculty of Chemistry and Chemical Technology, University of Ljubljana (retired) Vecna pot 113, 1000 Ljubljana, Slovenia * Corresponding author: E-mail: a.perdih@gmail.com Received: 17-02-2016 Abstract The concept of branching degrees is introduced. In the case of octane isomers it is derived from the values of a set of their physicochemical properties, calculating for each isomer the average of the normalized values and these averages are defined as branching degrees of octane isomers. The sequence of these branching degrees of octane isomers does not differ much from the »regular« one defined earlier. 2,2-Dimethylhexane appears to be less branched than 3,4-dimethyl-hexane and 3-ethyl, 2-methylpentane, whereas 2,3,4-trimethylpentane appears to be less branched than 3-ethyl, 3-methylpentane. While the increasing number of branches gives rise to increasing branching degrees, the peripheral position of branches and the separation between branches decreases the value of the branching degree. The central position of branches increases it. A bigger branch increases it more than a smaller one. The quantification of these structural features and their correlations with few indices is given as well. Keywords: Branching degree, Distance number, Number of branches, Octanes, Peripheral number, Size of the largest branch 1. Introduction Branching of alkanes is a concept to which much attention had been paid. For example, Bonchev and Trinajsti}1 formulated several general rules for branching based on Wiener2 index that were improved later.3 Randic4 reminded that branching was in fact attempted to be defined using few topological indices, either the Wiener index2 or the largest eigenvalue of the adjacency matrix5,6 and he provided the largest eigenvalue of the path matrix as a new basis for the definition of branching.4 Randic and Wilkins7 followed with the ordering of structures based on path indices. Later8 were presented »regular«, in part intuitively derived sequences of octane isomers of increasing branching, one of them being Oct < 2M7 < 3M7 < 4M7 < 3Et6 < 25M6 < 24M6 < 23M6 < 34M6 < 3Et2M5 < 22M6 < 33M6 < 3Et3M5 < 234M5 < 224M5 < 223M5 < 233M5 < 2233M4, as well as the indices derived from a simplified version of the Universal matrix giving rise to such »regular« sequences of octane isomers. Such a »regular« sequence is observed among some of the indices912 V(a, b, c) = Vwm(a, b, c) and VL(a, b, c) as well as among some of the vertex degree weighted path one indices. Randic and Wilkins7 introduced and discussed the significance of the results of ordering of alkane isomers based on paths of length two (p2) and paths of length three (p3) as well as their conceptual value. The degeneration of p2 and p3, as well as their integer values enabled Randic and Wilkins7 to form rectangular grid graphs in form of coordinate systems similar to Mendeleev's periodic system of elements. In present paper there is made an attempt to quantify the positions of octanes in the »regular« sequences of octane isomers based on some physicochemical properties (PCP) of them, the sequences of which are the closest to the »regular« sequence. Octanes were chosen since this is the largest group of alkane isomers for which a number of data is known for all or most of isomers. 2. Notation and Physicochemical Properties of Octane Isomers Notations and physicochemical properties of octane isomers were presented in a previous paper.9 3. Derivation of Sequences The software for statistics calculations included in the program package MS Excel was used. Perdih : Introduction of branching degrees of octane isomers 412 Acta Chim. Slov. 2016, 63, 411-415 The physicochemical properties of octane isomers were chosen in such a way that between their values and the »regular« equidistant sequence of octane isomers of increasing branching being8 Oct < 2M7 < 3M7 < 4M7 < 3Et6 < 25M6 < 24M6 < 23M6 < 34M6 < 3Et2M5 < 22M6 < 33M6 < 3Et3M5 < 234M5 < 224M5 < 223M5 < 233M5 < 2233M4, to which the integer values of 1 to 18, respectively, were ascribed, the correlation coefficient was |R| > 0.90. This criterion was fulfilled for the following physicochemical properties of octanes: Octane Numbers (MON, BON, RON), reduced boiling point (BP/Tc), the van der Waals parameters a0 and b0 represented here by the ratios Tc/Pc and Tc2/Pc, respectively, the Antoine constant C, the Pitzer's acentric factor ra, and the entropy S. Then, the values of these physicochemical properties were normalized relatively to the number of branches in the octane isomers in such a way that the normalized values in the case of n-octane (Oct) were equal to 0 (zero), and in the case of 2,2,3,3-tetramethylbutane (2233M4) were equal to 4. In the case of Octane Numbers, for which the experimental values for 2,2,3,3-tetramethylbutane were not known, the normalized values for 2,3,3-trimethylpen-tane were ascribed to be equal to 3. After normalization of the values of these physicochemical properties, the average of the normalized values for each isomer was calculated and these averages are defined as branching degrees of octane isomers. The peripheral number Nper is defined as Xdsy, where dsy is the distance of a branch from the axis of symmetry of the main chain of the molecular graph. The distance number Nd is defined as the distance between two branches. The size of the largest branch Lbr is equal to the number of vertices in the branch. 4. Results and Discussion MON -s— TcîiPc EON —1— EFÎTc RON -s C -Tefc w # average IÛ ift !£l (O if) ID IT) Lf) ID -i SSE2SSSEE2 fl- rt rt c*5 .■¡i w SI N fl rt UJ OJ M CM CN ÇN « 1M Figure 1. Normalized values of physicochemical properties of octane isomers and their average. Figure 2. Sequence of octane isomers of increasing branching based on data of the branching degrees derived from their physicochemical properties. The resulting branching degrees of octane isomers are presented for the »regular« sequence of octane isomers in Figure 1, whereas the sequence of octanes using these branching degrees of octane isomers together with their values is presented in Figure 2 as well as in Table 1. The sequence of branching degrees of octane isomers derived using the data for the physicochemical properties of octanes: MON, BON, RON, BP/Tc, Tc/Pc, Tc2/Pc, C, ra, and S, which is Oct < 2M7 < 3M7 < 4M7 < 3Et6 < 25M6 < 24M6 < 23M6 < 22M6 < 34M6 < 3Et2M5 Table 1. Branching degrees of octane isomers derived from the normalized data of the physicochemical properties of octanes as well as the measures of structural Oct 2M7 3M7 4M7 3Et6 25M6 24M6 23M6 22M6 34M6 3Et2M5 33M6 Deg.PCP 0 0.72 0.90 0.98 1.25 1.41 1.69 1.72 1.79 1.90 2.09 2.14 Deg.VL 0 0.69 0.89 0.95 1.15 1.42 1.62 1.71 1.86 1.86 1.93 2.16 Nbr 0 1 1 1 1 2 2 2 2 2 2 2 Nper Nd 0 2 1 0 0.5 3 2 2 3 1 1 1 3 2 1 0 1 1 0 Lbr 0 1 1 1 2 1 1 1 1 1 2 1 Deg.PCP - Branching degrees derived from the physicochemical properties of octanes: MON, BON, RON, BP/Tc, Tc/Pc, Tc2/Pc, C, ra, and S as the average of the Deg.VL - Branching degrees derived from the values of index VL(-0.126, -0.139, -0.27). Nbr - number of branches, Nper - peripheral number, Nd - distance number, Lbr - the size of the largest branch. Perdih : Introduction of branching degrees of octane isomers Acta Chim. Slov. 2016, 63, 411-415_ 413 Table 2. Correlation of physicochemical properties of octanes with the branching degrees presented in Table 1 (R br. deg.) sorted by |R|, with the »regular« equidistant sequence of octane isomers (R »reg.«), with the number of branches (R Nbr), with the peripheral number (R Nper), with the distance number (R Nd) as well as with the size of the largest branch (R Lbr). PCP R br. deg. R »reg« R Nbr R Nper R Nd R Lbr br. deg. 1 0.961 0.959 0.300 -0.237 0.283 m -0.993 -0.969 -0.941 -0.264 0.226 -0.244 RON 0.979 0.943 0.974 0.408 -0.357 0.333 BON 0.976 0.934 0.965 0.395 -0.241 0.373 BP/Tc -0.976 -0.943 -0.893 -0.114 0.356 -0.287 Tc2/Pc -0.976 -0.944 -0.964 -0.402 0.111 -0.311 MON 0.969 0.911 0.932 0.357 -0.485 0.445 Tc/Pc -0.963 -0.923 -0.878 -0.073 0.433 -0.374 C 0.957 0.929 0.914 0.306 -0.085 0.196 S -0.941 -0.938 -0.902 -0.324 0.132 -0.153 R2 -0.874 -0.865 -0.903 -0.393 0.111 -0.320 AHv -0.850 -0.865 -0.893 -0.628 -0.298 -0.104 Pc 0.846 0.801 0.714 -0.189 -0.519 0.368 A -0.659 -0.768 -0.726 -0.581 -0.258 -0.126 Vc -0.622 -0.629 -0.498 0.156 0.512 -0.552 BP -0.619 -0.619 -0.732 -0.808 -0.500 -0.013 AHf°g 0.617 0.611 0.718 0.792 0.397 -0.124 dc 0.609 0.620 0.485 -0.159 -0.499 0.541 ac -0.594 -0.695 -0.603 -0.192 0.166 -0.317 logVP 0.586 0.556 0.668 0.587 0.508 0.038 MR -0.585 -0.507 -0.540 0.312 0.506 -0.398 Zc 0.582 0.515 0.611 0.296 0.072 -0.153 d 0.495 0.447 0.570 -0.084 -0.257 0.114 Vm -0.489 -0.441 -0.569 0.116 0.290 -0.137 nD 0.429 0.397 0.548 -0.046 -0.214 0.066 B -0.251 -0.420 -0.411 -0.801 -0.530 0.054 Tc 0.152 0.123 -0.035 -0.753 -0.606 0.223 ST -0.137 -0.161 -0.342 -0.858 -0.600 0.228 CED 0.101 -0.070 -0.036 -0.522 -0.403 0.052 Sol.par. 0.091 -0.062 -0.046 -0.530 -0.409 0.054 Meaning of acronyms for physicochemical properties of octanes: ffl: Pitzer's acentric factor, BON, MON, RON: Octane Numbers, Tc2/Pc: represents the van der Waals parameter b0, BP/Tc: reduced boiling point, Tc/Pc: represents the van der Waals parameter a0, S: entropy, A, B, C: Antoine constants, AHv: enthalpy of vaporisation, R2: quadratic mean radius, Pc: critical pressure, AHf°g: standard enthalpy of formation for the ideal gas, BP: boiling point, logVP: vapour pressure, Zc, ac, Vc, dc, Tc: critical data, MR: molar refraction, d: density, Vm: liquid molar volume, nD: refractive index, ST: surface tension, CED: cohesive energy density, Sol.par.: solubility parameter. < 33M6 < 234M5 < 3Et3M5 < 224M5 < 223M5 < 233M5 < 2233M4, does not differ much from the »regular«8 one, which is Oct < 2M7 < 3M7 < 4M7 < 3Et6 < 25M6 < features. 234M5 3Et3M5 224M5 223M5 233M5 2233M4 2.52 2.56 2.59 2.75 2.87 4 2.51 2.40 2.64 2.90 2.99 4 3 2 3 3 3 4 2 0 3 2 1 2 1 0 2 1 1 1 1 2 1 1 1 1 normalized values. 24M6 < 23M6 < 34M6 < 3Et2M5 < 22M6 < 33M6 < 3Et3M5 < 234M5 < 224M5 < 223M5 < 233M5 < 2233M4. They correlate to one another to R = 0.967. Only the isomer 22M6 appears to be less branched than 34M6 and 3Et2M5, as well as 234M5 appears to be less branched than 3Et3M5. The sequence of isomers of increasing branching, as well as the values of branching degrees based on physicochemical properties of octanes, confirm the previous conclusions based on topological indices1,3,4 that the most important structural feature regarding branching is the number of branches. In the case of the branching degrees of octane isomers derived here, it is overwhelmed only in the case of 234M5 < 3Et3M5. The next important previously1'3'4 known structural feature is the position of branches. The more peripherally positioned the branch the less Perdih : Introduction of branching degrees of octane isomers 414 Acta Chim. Slov. 2016, 63, 411-415 branched appears the octane. And vice versa, the more centrally is positioned the branch the more branched appears the octane, as for example in 2M7 < 3M7 < 4M7, in 25M6 < 24M6 < 23M6 < 34M6, as well as in 224M5 < 223M5 < 233M5. The sequence of 25M6 < 24M6 < 23M6 < 22M6 illustrates that the greater distance between branches being in this case 3 > 2 > 1 > 0 gives rise to a lesser branching degree. The sequences 4M7 < 3Et6, 23M6 < 3Et2M5, and 33M6 < 3Et3M5 illustrate that the bigger is a centrally positioned branch the more branched appears the octane. Only in the case of 234M5 < 3Et3M5 the combined central position of two branches, one small and one bigger, and the zero distance between them slightly overwhelm the influence of the number of branches being one distance unit apart, where two of the three are peripheral. Thus, the peripheral position of branches decreases the value of branching degree presented by the number of branches, whereas the central position of branches increases it. The separation between branches decreases it as well. A bigger branch increases it more than a smaller one. The sequences of values of particular physicochemi-cal properties of octanes deviate more or less from the sequence of branching degrees of octane isomers derived here. Whereas in the »regular« sequence of octane isomers there prevails the influence of the number of branches over the joint influence of the position of branches, the separation between them, and the type of branches, in the sequence of the branching degrees of octane isomers derived here, there is one exception to this rule. In the real values of physicochemical properties of octanes, the lower is the value of |R| br. deg. presented in Table 2 the less influence on their values has the number of branches and the more the other structural features. One of the most illustrative examples in this respect is Tc, Table 2, correlating to the branching degree to R = 0.152, to the »regular« sequence of octane isomers to R = 0.123, and to the number of branches Nbr to R = -0.035. In the case of Tc, the influence of the position of branches appears to be deciding. The peripherally positioned branches give rise to lower values of Tc, whereas the centrally positioned branches give rise to higher values of Tc. As a consequence, Tc correlates to the peripheral number Nper to R = -0.753, whereas to the distance number Nd to R = -0.606 and to the size of the largest branch Lbr to R = 0.223. br This is in contrast to Tc2/Pc, correlating to the branching degree to R = -0.976, to the »regular« sequence of octane isomers to R = -0.944, whereas it correlates to Nbr to R -0.964, to Nper to R = -0.402, to Lbr to R -0.311, and to Nd to R = 0.111 only. Other interesting example, where the correlations are low, are the critical properties Vc and dc where |R| Lbr > |R| Nd > |R| Nbr > |R| Nper, indicating that the size of the branch is the most important at these physicochemical properties. Another interesting example, where the corre- lations are very low, are the cohesive energy density (CED) and the solubility parameter (Sol. par.), where |R| Nper > |R| Nd >> |R| Lbr > |R| Nbr. Other comparisons can be made as well, using data in Table 2. The measures of structural features presented in Table 1 correlate with one another to a low degree. This is presented in Table 3. Table 3. Correlations (R) between the measures of the structural features presented in Table 1. Nbr Nper Nd Lbr Nbr Nper Nd 1 0.512 0.079 1 0.545 1 Lbr 0.129 -0.179 -0.297 1 Branching degrees of octane isomers were not intended to represent a new index but to be only a quantitative illustration of the degree of branching of octane isomers as it is felt by a group of their physicochemical properties. Previous12 results have shown that topological indices, which describe the »regular« sequence of octane isomers, are not good indices for physicochemical properties of octane isomers. This is reflected in Table 2 also for the branching degrees of octane isomers, where only the Pit-zer's acentric factor ra exceeds the lower limit of usefulness of R = 0.99.13 However, the comparison of their goodness with that of a previously published index group, namely p2/w2 and p/w3,14 where only one physicochemical property of octane isomers, namely MR, slightly exceeds the limit value13 of R = 0.99, indicates the values of R of similar level. Indices giving rise to better goodness regarding the physicochemical properties of octane isomers were presented elsewhere.9,12 Sequences of structural features Nbr, Nper, Nd and Lbr according to the sequence of the absolute values of their correlation coefficients |R| (R given in parentheses) are at the branching degree and some indices as follows: Branching degree p2/w2:14 p3/w3 :14 .here p4/w4: W:2 14 Nbr (0.959) > Nper (0.300) > Lbr (0.283) > Nd (-0.237) Nbr (0.986) > Nper (0.489) >> Lbr (0.080) > Nd (-0.022) Lbr (0.539) > Nd (-0.352) > Nbr (0.500) > Nper (-0.329) Nbr (-0.771) > Nper (-0.502) > Lbr (0.276) > Nd (-0.059) Nbr (-0.918) > Lbr (0.388) > Nd (0.366) > Nper (-0.201) Nbr (0.942) > Nd (-0.322) > Lte (0.284) > Nper (0.243) Nbr (-0.953) > Nper (-0.603) > Nd (-0.076) > Lbr (0.031) Vl(-0.126, -0.139, -0.27): Nbr (0.968) > Nper (0.330) > Lbr (0.226) > Nd (-0.223) RW: .15 X: .16 Perdih : Introduction of branching degrees of octane isomers Acta Chim. Slov. 2016, 63, 411-415 415 Interesting is the remarkable correlation (R = 0.991) of RW with the degree of branching of octanes presented here. However, due to a higher influence of the distance between branches, Nd, the RW differs from the degree of branching of octanes in partial sequences 25M6 < 3Et6 and 224M5 < 234M5. While RW = VL(0, 0, -1), cf. ref.910, the index VL(-0.126, -0.139, -0.27) correlates to the branching degree of octanes derived here to R = 0.996 and gives the sequence of octane isomers Oct < 2M7 < 3M7 < 4M7 < 3Et6 < 25M6 < 24M6 < 23M6 < 22M6 < 34M6 < 3Et2M5 < 33M6 < 3Et3M5 < 234M5 < 224M5 < 223M5 < 233M5 < 2233M4, which is regarding the intuition better than that of the degree of branching of octanes derived above since in it there exists the sequence 3Et3M5 < 234M5 and not 234M5 < 3Et3M5. Different indices depend thus differently on the structural features of octanes, therefore the grouping of physicochemical properties of octanes based on correlations with them14 varies with their properties and is not necessarily equal to that derived by the intercorrelation of physicochemical properties of octanes themselves.9 The results presented in Table 2 indicate also some classification of physicochemical properties of octanes. It can be compared to the classification based on the indices p/w;.,14 as well as to that based on correlations between the physicochemical properties of octanes.9 5. References 1. D. Bonchev, N. Trinajstic, J. Chem. Phys. 1977, 67, 45174533. http://dx.doi.Org/10.1063/1.434593 2. H. Wiener, J. Am. Chem. Soc. 1947, 69, 17-20. http://dx.doi.org/10.1021/ja01193a005 3. D. Bonchev, J. Molec. Struct. (Theochem), 1995, 336, 137156. http://dx.doi.org/10.1016/0166-1280(94)04081-3 4. M. Randic, Acta Chim. Slov. 1997, 44, 57-77. 5. L. Lovasz, J. Pelikan, Period Math Hung. 1973, 3, 175-182. http://dx.doi.org/10.1007/BF02018473 6. D. M. Cvetkovic, I. Gutman, Croat. Chem. Acta, 1977, 49, 115-121. 7. M. Randic, C. L. Wilkins, J. Phys. Chem. 1979, 83, 15251540. http://dx.doi.org/10.1021/j100474a032 8. A. Perdih, Indian J. Chem, 2003, 42A, 1246-1257. 9. A. Perdih, Acta Chim. Slov. 2015, 62, 879-888. http://dx.doi.org/10.17344/acsi.2015.1607 10. A. Perdih, B. Perdih, Acta Chim. Slov. 2004, 51, 598-609. 11. A. Perdih, Acta Chim. Slov. 2015, 62, 385-388. http://dx.doi.org/10.17344/acsi.2014.1164 12. A. Perdih, Acta Chim. Slov. 2016, 63, 88-96. http://dx.doi.org/10.17344/acsi.2015.1975 13. Z. Mihalic, N. Trinajstic, J. Chem. Educ. 1992, 69, 701-712. http://dx.doi.org/10.1021/ed069p701 14. M. Randic, J. Chem. Inf. Comput. Sci. 2001, 41, 607-613. http://dx.doi.org/10.1021/ci0001031 15. M.V. Diudea, J. Chem. Inf. Comput. Sci. 1997, 37, 292-299. http://dx.doi.org/10.1021/ci960037w 16. M. Randic, J. Am. Chem. Soc. 1975, 97, 6609-6615. http://dx.doi.org/10.1021/ja00856a001 Povzetek Uveden je pojem stopnja razvejanosti. Vrednosti stopnje razvejanosti so izračunane iz normaliziranih vrednosti skupine fizikokemijskih lastnosti oktanov. Zaporedje teh vrednosti ne odstopa veliko od »regularnega« zaporedja določenega prej. Izračunane stopnje razvejanosti oktanov kažejo, da je 2,2-dimetilheksan manj razvejan kot sta 3,4-dimetilheksan in 3-etil,2-metilpentan, medtem ko je 2,3,4-trimetilpentan manj razvejan kot 3-etil,3-metilpentan. Medtem ko večanje števila vej povečuje vrednost stopnje razvejanosti, jo robni položaj vej in razdalja med vejami zmanjšujeta. Sredinski položaj vej jo povečuje. Večje veje jo povečajo bolj kot majhne. Podano je tudi vrednotenje teh strukturnih značilnosti in njihove korelacije z nekaterimi indeksi. Perdih : Introduction of branching degrees of octane isomers 416 S78 Acta Chim. Slov. 2016, 63, (2), Supplement DRU[TVENE VESTI IN DRUGE AKTIVNOSTI SOCIETY NEWS, ANNOUNCEMENTS, ACTIVITIES Vsebina Jezuitski kemiki v Habsburški monarhiji ..................................................................S65 Poročilo o delu v letu 2015 ........................................................................................S77 Koledar važnejših znanstvenih srečanj s področja kemije, kemijske tehnologije in kemijskega inženirstva..........................................................S79 Navodila za avtorje ......................................................................................................S86 Contents Jesuits Chemists of Hapsburg Monarchy ..................................................................S65 Report for 2015 ..........................................................................................................S77 Scientific meetings - chemistry, chemical technology and chemical engineering . . S79 Instructions for authors ..............................................................................................S86 Dru{tvene vesti in druge aktualnosti S64 _Acta Chim. Slov. 2016, 63, (2), Supplement Društvene vesti in druge aktivnosti DOI: 10.17344/acsi.2016.2467 Acta Chim. Slov. 2016, 63, (2), S65-S75 S65 Jezuitski kemiki v Habsburški monarhiji Stanislav Južnič * Corresponding author: E-mail: juznic@hotmail.com Telephone: 031 814 742 Pozetek Opisani so dosežki jezuitov iz Avstrijske in Češke province, ki so objavljali knjige o kemiji. Posebej so izpostavljene njihove povezave z območjem današnje Slovenije. Nakazane so smernice s katerimi so omogočili uren prodor idej o strukturi snovi jezuita Ruderja Boškovica. Nepojmljivo hitro uveljavljanje Boškovicevih pristašev v Habsburški monarhiji je primerjano s podobno hitro uveljavitvijo kinetičnih teorij atomov Slovenca Jožefa Stefana in z napol Slovenko poročenega Ludwiga Boltzmanna v istih zemljepisnih območjih. Ključne besede: Jezuiti, Habsburška monarhija, zgodovina kemije, Ruder Boškovic, Jožef Stefan, Ludwig Boltzmann 1. Uvod Srednja Evropa je v marsičem enaka ranjki Habsburški monarhiji. Jezuiti so v njej razvijali kemijske vede nekoliko mimo državnih meja, saj sta Avstrijska in Češka jezuitska provinca pokrivali tudi bavarski Passau in poljsko Slezijo, ki jo je Mariji Tereziji »ukradel« Friderik Veliki. Po drugi strani pa je Tirolska pripadala Zgornje-nemški provinci. Razvoj kemije in sorodnih tehniških zanj v Avstrijski jezuitski provinci je bil v veliki meri osredotočen na njen vzhodni z rudami bogati del v Slovaški in Transilvaniji, ki sta politično pripadali ogrski polovici Habsburške monarhije. Dunaj in Praga sta bila resda intelektualni središči, vendar pa sta sredi 18. stoletja svoje kemijskim uporabnim vedam namenjene spodbude prejemala predvsem od jezuitov odraslih in vzgojenih v rudarsko-indu-strijskih območjih Karpatov. Jezuitom se je ob Karpatih posrečilo razviti dve pomembni univerzi v slovaških Košicah in transilvanskem Cluju, sčasoma pa tudi v Bratislavi in danes ukrajinskem Uzhhorodu. Pomembno središče pod Karpati je bil jezuitski noviciat v Banski Bystrici, za razvoj kemije pa je bilo najpomembnejše Idriji sorodno rudarsko mestece Banska Stiavnica (Schemnitz) v katerem je Marija Terezija ustanovila svojo prvo Rudarsko akademijo s izbornimi profesorji med katerimi so bili dotedanji idrijski zdravnik-kemik Scopo-li, nizozemski kemik Jacquin, nekdanji jezuit Ignaz von Born, ptujski jezuit Tirnberger in njegov sobrat Nikolaus Poda von Neuhaus. V danes slovenskih rudarskih središčih Idrijskega ali zasavskega območja jezuiti niso ustanovili svojih postojank, so pa o njih pisali in jih raziskovali tudi po kemijski plati; tu gre predvsem za dela, ki so jih postorili prvi eksperimentalni kemik vzgojen na danes slovenskem ozemlju Franz Muhlpacher in Tobija Gruber, brat bolj znanega Gabrijela. 2. Začetki jezuitske kemije v v Avstrijski in Ceski provinci Jezuitska kemija se je, seveda, začela s svojo eksotično polsestro alkimijo, ki je imela mogočno podporo v cesarjih od praškega Rudolfa II. do dunajskega Leopolda I. Velik del alkimističnega početja je imel globokoumen značaj; njihova navezanost na uporabno kemijo industrijske proizvodnje in rudarjenja pa je bila temeljna, saj je bila osnova vseh alkimističnih pretvorb - idrijsko živo srebro. Bistven del jezuitskega uspeha pa so bile knjige o kemiji in drugih vedah, ki so jih naravnost množično proizvajali za večjo slavo svojega reda. 3. Rimska naveza Sv. Ignacij je svojim jezuitom odsvetoval študij na medicinskih fakultetah, kar je bila mogočna cokla jezuitske kemije, ki se je med naprednimi Evropejci v veliki meri razvijala v povezavi z farmacijo in zdravljenjem. Ta nesmiselna prepoved je izvirala iz Ignacijeve osebne zamere do zdravnikov, ki mu med zdravljenjem v bojih poškodovane noge niso nikoli znali preprečiti šepanja, je delala preglavice mnogoterim generacijam jezuitov. Tako so Athanasius Kircher in njegova učenca Gaspar Schott v bavarskem Wurzburgu ali Francesco Lana Terzi v Brescii svoje alkimistične razprave s praktičnimi navodili izdelave filozofskega kamna vred raje skrivali v mogočne knjige z drugačnimi zavajajočimi naslovi, saj si niso izrecno Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji S66 Acta Chim. Slov. 2016, 63, (2), S65-S75 Graf 1: Število objavljenih kemijskih-fizikalnih knjig jezuitov avstrijske in češke province od skupno 616, med njimi 72 izpod peres ljubljanskih jezuitov, 29 pa od onih, ki so fiziko in/ali matematiko predavali tudi v Ljubljani. želeli alkimistične slave. Kircher je svoje poglavitno alki-mistično poglavje knjige Oedipus Aegyptiacus posvetil Janezu Vajkardu knezu Turjaškemu, ki je bil med smetano tedanje Evrope znan po svojih medicinskih in alkimi-stičnih znanjih. Med svojo izmenjavo mnenj s praškim profesorjem Marcusim Marcijem je skoval temelje tedanjih alkimističnih kotenj. Lana Terzi je kakopak trdil, da je celo sam proizvedel »dušo zlata« in z njo izvedel par manjših transmutacij.1 4. Nizozemska naveza Ob rimskem si velja ogledati še nizozemski vpliv na razvoj jezuitske kemije v Habsburški monarhiji; le-ta bi utegnil biti celo bolj merodajen in trajnejši, saj sta mu postavila piko na i komaj Van Swieten, Jacquin in Jan Ingen-housz ob zatonu jezuitskega reda. Nizozemec španskega rodu Martin Del Rio je med prvimi zanesel nove kemijske in alkimistične prijeme v Avstrijsko jezuitsko provinco kot profesor v Gradcu. Ob nastopu v Gradcu je že imel v žepu prvo izdajo svoje najbolj odmevne knjige proti magiji, ki pa jo je strogo ločeval od alkimije; podpiral je možnost izdelave kamna modro-sti.2 Iz Del Riovega okolja je izšel Francois d'Aguilon, ki je v Antwerpnu leta 1596 lastnoročno proizvajal zlato v posodah z jezuitskim žigom pred zvedavimi očmi očeta slikarja Rubensa in kemika Johannesa Baptiste van Hel-monta.3 Francois d'Aguilon je nato objavil odmevno knjigo o optiki z Rubensovimi risbami in v svoji antwerpen-skih učilnicah od leta 1611 ob pomoči Gregoira Saint-Vincenta izšolal številne jezuite Avstrijske in Češke province vključno s prvim olomuškim profesorjem fizike s kemijo Theodorjem Moretom (Moretus) in vodilnim nizozemskim matematikom Andree Tacqetom. Med zgodnjimi jezuiti zainteresiranimi za alkimijo je bil antwerpenski jezuit Ignatius Derkennis (Der Ken-nis,* 1589; t1656), učenec raziskovalca kvadrature kroga Gregoira de Saint-Vincenta, ki se je svojih modrosti učil v Rimu pri Claviusu in Grienbergerju, čeravno je slednji nato kritiziral Saint-Vincentove prijeme. Saint-Vincent se je kemijskih modrosti navzel ob zatonu praškega alkimi-stičnega okolja po smrti cesarja Rudolfa in po odhodu Johannesa Keplerja iz Zlatega mesta. Kot se to pogosto zgodi, je dobi globokoumnega iskanja vladarja Rudolfa in misleca Keplerja sledil rušilni napad nevednih pohlepnežev, za tisti nesrečni čas imenovan Tridesetletna vojna. Saint-Vincent je moral na vrat-na nos odpeketati iz zlate Prage kar brez zasnov svojih knjig. Podobno se je zgodilo drugemu velikemu sopotniku zgodnje kemije Athanasiusu Kircherju na Nemškem. Medtem ko je Kircher poslal ugledni rimski jezuitski profesor, se je Saint-Vincent raje vrnil domov na Nizozemsko in tam, med drugim, vzgojil Derkennisa. Derkennisova leuvenska predavanja so bila tako znamenita, da jih je obiskal celo škof Juan Caramuel Lobkowitz. Med Derkennisovimi študenti je bil tudi bodoči praški matematik Belgijec Joannes Weyer (*1598; t1575) Derkennisova zgodnja jezuitska kemija s kritiko Descartesa in B. Pascalovih janzenistov je v avstrijski jezuitski provinci našla svoj odmev predvsem pri Gradčanu Leopoldu Galleru (1683; t1761). Galler je o kemiji pisal kot dunajski profesor kemije in fizike znotraj filozofije leta 1718, desetletji pozneje pa je postal profesor starih spisov in knjižničar v Ljubljani leta 1736; njegov starejši brat Maksimilijan je bil dolgoletni profesor fizike s kemijo in ljubljanski rektor od 15. 11. 1716 do 24. 9. 1719. Oba imamo lahko za začetnika kemijskih snovanj med Slovenci pod vplivom dunajskega ko-merčnega svetnika od leta 1666 Johanna Joachima Bec- Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji Acta Chim. Slov. 2016, 63, (2), S65-S75 S67 Spodn je štajerski profesorji: število letnikov predavanj filozofije s fiziko od skupno 76 Kranjski profesorji: število letnikov predavanj filozofije s fiziko od skupno 481 Goriški profesorji: Število letnikov predavan j filozofije s fiziko od skupno 121 Koroški profesorji: število letnikov predavanj filozofije s fiziko od skupno 217 Hrvaški profesorji: število letnikov predavanj filozofije s fiziko od skupno 430 Graf 2: Domači kraji jezuitskih matematikov in fizikov-kemikov razporejenih po desetletjih rojstev. herja (* 1635; t 1682). Becher je imel do leta 1675 podporo dunajskega prvega ministra Albrechta VII. prvega grofa Zinzendorfa-Pottendorfa (* 1618; t1683), tekmeca žužemberško-ljubljanskega kneza Janeza Vajkarda Turjaškega. Janez je bil med dunajsko smetano daleč najvidnejši poznavalec medicine, alkimije in sodobnejšega eksperimentiranja in je do svoje odstavitve konec leta 1669 prav tako s prijaznim očesom opazoval Becherjeve domnevne tedaj zelo moderne transmutacije, v svojo ljubljansko knjižnico pa je uvrstil številne Becherjeve knjige, čeravno je bil Becher svojevrsten konkurent Janezovega favorita Athanasiusa Kircherja. Moža sta namreč zaporedoma objavila knjigi o kemiji podzemlja; potem ko je Kircher svojo knjigo naslovil Egipčanski Ojdip, mu je Becher pariral z naslovom Ojdip kemik. Iz Becherjevih snovanj je izšel flogiston Georga Ernsta Stahla (* 1659; t1734) in opredelil kemijsko miselnost za več generacij do Lavoisierjevih dni. Od Derkennisu je Leopold Galler navajal predvsem dela sobrata jezuita Thomasa Cevae (*1648 Milano; t1737 Milano), ki je deloval v tisti čas habsburškem Milanu pred prihodom svojega mlajšega sodobnika, jezuita Boškovica. Bil je brat matematika Johannesa Cevae (*1647 Milano; t1734 Mantova). Thomas je nasprotoval tako Descartesu kot Koperniku, pač prisegajoč na sobrate jezuite, kot je bil Riccioli v Bologni. Zanimal se je za alkimijo slovitega ustanovnega člana londonske Kraljeve družbe Kenelma Digbyja.4 5. Kemiki spod Karpatov Antonius Gabon (* 1677 Banska Bystrica na Slovaškem; fl735 Gyor) je bil že znanilec novih časov v katerih alkimija in kemija nista več izhajali iz filozofskih pobud, temveč iz praktičnega industrijskega okolja blizu rudnika v Banski Štiavnici. Študiral je matematične vede pri dolgoletnem trnavskem profesorju Joannesu Du-bovsky (Dobovski, Dubowsky), fiziko s kemijo pa pri An-dreasu Madotsaniju (Madotsany). Prvo knjigo je kot profesor humanistike v Trnavi naslovil Žalostno razvedrilo ali Petero nespametnih o zaklenjenih modrostih, drugo pa je kot tamkajšnji profesor fizike s kemijo posvetil eksotični fiziki z naravnimi in umetnimi skrivnostmi narave.5 Opisal je kemijske postopke utemeljene na praktičnem znanju o živalih, žuželkah, barvah, rastlinah, drevesih, sadju in likerjih. Dodal je še uporaben slovar tehniških nazivov v štirih jezikih s katerimi je prihajal v stik: latinsko, madžarsko, nemško in češko. Gabon je kot kratkohlačnik opazoval hrumenje turških čet, ki so skušale podjarmiti cesarski Dunaj kot ključ do oblasti v srednjeevropskem Podonavju. Seveda pa ni šlo zgolj za vojno, temveč predvsem za izmenjavo tehnoloških dosežkov dveh sicer sprtih kultur, ki se je, med drugim, izcimi-la tudi v nove dunajske obrede ljubiteljev kave. Orientalski vplivi so zasvojili dunajske tehniške vede predvsem z Josep-husom Franzom (Frantz, * 1704; 11776) in Erazmom Frolichom. Franz je med prvimi na veliko prevajal iz Stanislav Južnič: Jezuitski kemiki v Habsburški monarhiji S68 Acta Chim. Slov. 2016, 63, (2), S65-S75 turščine po obisku Carigrada leta 1740, ko mu je cesarica zaupala vodenje Orientalske akademije. Pisal je o astronomiji, še več pa o električnem telegrafu ob razmišljanjih o naravi elektrike. Svojih kemijskih zapiskov zvečine resda ni dal spustiti skozi tiskarske preše, a v njegovih časih so rokopisi prav tako urno krožili med znanja žejnimi bralci.6 Prvo sodobno kemijsko metalurgijo je med habsburškimi jezuiti objavil Hrvat z današnje meje med Slovaško in Ogrsko Josephus Bartakovics (Bartakovic, * 1722; f1763). Matematične vede je leta 1742 študiral v Košicah pri Georgu Egereiju, ki jih je predaval domala na vseh kolegijih Avstrijske province vključno z Ljubljano. Bartakovic je kot mlad magister trnavski predavatelj po praktičnih izkušnjah nabranih že spod Karpatov objavil Metalurgijo s postopki pridobivanja zlata in srebra. Tako kot dve desetletji pred njim Gabon, je tudi Bartakovic na konec postavil še slovar tehniških izrazov, vendar to pot zgolj trojezični brez češčine. Dodal je še analizo mineralnih voda, ki jih je bilo na njegovem območju obilo skupaj s številnimi toplicami.7 Bratislavčan Joannes Fridvalski (Fridvalszki, *1730; f1784) je specializiral matematične vede na Dunaju pri Jo-sefu Danielu, nato pa jih je desetletje predaval v transilvanskem Cluju. S terenskim delom se je dokopal do spoznanj o transilvanskem rudnem bogastvu, veliko pa je prispeval k kemijskim postopkoma za posodobitev izdelave papirja. Eksperimentiral je z rastlinami in popisal ogrske in transilvanske rudnike železa in železarne, predvsem pa njihove bogate lastnike. Prisegal je na mineraloški sistem Johna Henryja Gottloba de Justija (* 1717; f1771) objavljen pri gottingenski akademiji. Fridvalski je študiral fiziko s kemijo na dunajski univerzi leta 1751 pri promotorju Boško-vičeve fizike Franciscusu Ginthorju (Gindhor) medtem ko je Justi predaval na sosednjem Terezijanišču od 1750 do 1753 v sodelovanju s poglavitnim terezijanskim politikom Friedrichom Wilhelmom grofom von Haugwitzom, vendar je Justi pozneje pri Frideriku Velikem potegnil ta kratko. Ravno med Fridvalskijevim študijem je Bavarec Ginthor prvi v Srednji Evropi promocijsko ponatisnil Boškovicevi knjigi o gravitacijskem pospešku v različnih točkah Geoi-da v čast (in plačilo) študentu Josephu de Seppenburgu in o zametkih Boškoviceve teorije točkastih središč sil v čast (in plačilo) študentu Carlu de Reutterju (* 1734; f1805).8 Reutter je bil promoviran v bakalavra pri Ginthorju že leta 1751 kot najstarejši sin dunajskega skladatelja Georga Reuterja (* 1708; f1772). Tudi sam je postal glasbenik violinist, kot cistercijan pa se je preimenoval v Ma-rian(usa).9 Fridvalski in njegovi sošolci leta 1751 niso bili promovirani, na seznamu novih bakalavrov pa je bil med študenti-jezuiti le repetitor hebrejščine Karl Mayr. Franciscusu Ginthor je bil mlajši brat knezoškofa in Passaua Josepha Antona Gindhora (* 1713; f1791), leta 1738/39 pa je v Ljubljani predaval humanistiko in vodil kongregacije. Po predavanjih fizike s kemijo v Passau in na Dunaju je postal profesor teologije, tato je vmesno predpostaviti, da ga je k promociji Boškovicevih del nagovoril so- delavec dunajski profesor matematike Karl Scherffer, ki se Ginthor prvi v Srednji Evropi promocijsko ponatisnil Boškovicevi knjigi o gravitacijskem pospešku v različnih točkah Geoida v čast (in plačilo) študentu Josephu de Seppenburgu in o zametkih Boškoviceve teorije točkastih središč sil v čast (in plačilo) študentu Carlu de Reutterju (* 1734; f1805).8 Reutter je bil promoviran v bakalavra pri Ginthorju že leta 1751 kot najstarejši sin dunajskega skladatelja Georga Reuterja (* 1708; f1772). Tudi sam je postal glasbenik violinist, kot cistercijan pa se je preimenoval v Marian(usa).9Fridvalski in njegovi sošolci leta 1751 niso bili promovirani, na seznamu novih bakalavrov pa je bil med študenti-jezuiti le repetitor hebrejščine Karl Mayr. Franciscusu Ginthor je bil mlajši brat knezoškofa in Passaua Josepha Antona Gindhora (* 1713; f1791), leta 1738/39 pa je v Ljubljani predaval humanistiko in vodil kongregacije. Po predavanjih fizike s kemijo v Passau in na Dunaju je postal profesor teologije, zato je vmesno predpostaviti, da ga je k promociji Boškovicevih del nagovoril sodelavec dunajski profesor matematike Karl Scherffer, ki se je pravkar vrnil na Dunaj z graške katedre za matematiko in astronomijo in je v naslednjih letih poslal poglavitni Boškovičev sodelavec in promotor. Leta 1751 je pri J. Da-nielu matematične vede specializiral Paul Mako, ki je kmalu postal vodilni zagovornik Boškovica. Fridvalski pa se je raje usmeril bolj v uporabne kmetijske vede. Pri poskusih z železovo rudo in antimonom se je Fridvalski sklicaval na Boerhaaveja, pri svincu pa na Johannesa Kunckela. Živo srebro je skupaj z antimonom, bizmutom, cinkom in arzenom štel k semi-kovinam in ni pozabil navesti njegove uporabe v alkimiji. Transilvanska nahajališča arzena je hvalil že Šved Johan Gottschalk Wallerius (*1709; f1785), poskuse pa je objavil Lomono-sov učitelj Johann Friderich Henckel. Fridvalski je opisal velika nahajališča nafte pod Karpati že pred B. Hacque-tom, delal pa je tudi poskuse z destilacijo. Podobno kot tri desetletja pred njim Bartakovic, je v zaključku popisal lokalne mineralne vode in toplice.10 Tik pred prepovedjo jezuitov je 24. 6. 1773 objavil še svoje poskuse s transilvanskim navadnim rujem »Rhus Cotinus Coriaria, Rhus Coti-nus Linnaei« in ga primerjal s podalpsko, torej tudi s kraško Scopolijevo inačico.11 Gradiščan Matthaeus Pankel (Pankl, * 1740; f1798) je specializiral matematične vede pri poglavitnem trnav-skem strokovnjaku Josefu Fuhrerju. Fiziko z Lavoisierje-vimi novostmi proti flogistonski kemiji je predaval v Tr-navi, po preselitvi univerze pa ni odšel z njo v Budo, temveč je nadaljeval s predavanji v Bratislavi vse do svoje smrti. Takoj po Francoski revoluciji je objavil zajeten učbenik leta 1790, malo pred Lavoisierjevo smrtjo pa ga je leta 1793 prvič priredil za Lavoisierjevo kemijo brez flogistona po vzoru na dunajska nizozemska barona Jac-quina. Panklov opis razvoja strukture svetlobe je citiral celo Goethe. Zelo odmevna je bila Panklova kmetijska kemija z madžarskim, latinskim in slovanskim kazalom; po njej so se zgledovali mnogi vključno s slovitim Liebigom Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji Acta Chim. Slov. 2016, 63, (2), S65-S75 S67 in našim Matijo Vertovcem.12 Panklov fizikalno-kemijski učbenik je povzemal pri J. Horvathu ob hvali induktivne metode Newtona. Horvath je bil poglavitni zagovornik Boškovica, vendar je v ponatisu svojega učbenika leta 1790 že previdno izpustil Boškovicevo krivuljo kot odmev dejstva, da so jezuiti z Boškovicem vred počasi izgubljali prestiž pri pouku fizike in kemije. Pankel je med prvimi posebno poglavje posvetil novi znanosti - kemiji. V tretjem delu učbenika je dodal še nekaj geofizike, geologije, fiziologije, fizične geografije in kozmogonije. Ni citiral zgolj poglavitnih nizozemskih učenjakov Boerhaa-veja in Muschenbroeka, temveč tudi najnovejše razprave na razmeroma sodoben način. 6. Prostozidarska naveza Učitelj Gabrijela Gruberja in številnih drugih Nikolaus Poda von Neuhaus, (Boda(nus), * 4. 10. 1723 Dunaj; SJ 22. 1. 1740 Dunaj; t 29. 4. 1798 Dunaj) se je praktičnih astronomskih prijemov naučil pri M. Hellu, da je lahko prevzel vodenje sicer ne najbolj uspešne graške astronomske opazovalnice med letoma 1758-1765. Graška predavanja so se mu zdela premalo obetavna kljub Gruberju in drugim prvovrstnim študentom, zato je leta 1765 kot graški profesor objavil knjigo o okoliških štajerskih rudnikih. Knjiga je privlekla pozornost cesarice, ki ga je imenovala za profesorja na novo ustanovljeni Rudarski akademiji v Banski Stiavnici. Tako se je Poda praktičnega dela svoje kemije priučil kot profesor v Banski Stiavnici med letoma 1766-1771. Predaval je mehaniko in hidravliko, zato ga je še posebej zanimala rudniška črpalka, ki jo je izdelal Karl, brat cesarskega astronoma Maksimilijana Hella. Nabiranje ledu v ustju naprave zaradi tedaj še neznanega Joule-Thomsonovega ohlajanja zraka ob širjenju v prazen prostor je tista leta vzbudila ogromno prahu, od poročila francoskega obiskovalca Lavoisierovega akademskega tekmeca Gabrijela Jarsa, do polemičnih člankov Erazma Darwina in njihovih kritik s strani Tobije Gruberja. Poda je črpalko narisal in opisal njeno delovanje.13 Med delom v Banski Stiavnici, njega dni bolj znani po nemškem imenu Schemnitz, je začel svoje sodelovanje z velikanom tedanje habsburške kemije in uporabnih ved, transilvanskim prostozidarjem Ignazom von Bornon (* 1742; SJ 1760-1762; t1791). Born se je jezuitski družbi priključil zgolj za bora tri leta, nato pa sta preteči meč prepovedi družbe, ki se je udejanjil desetletje pozneje, in Bornova prirojena hudomušnost zahtevali razpotje. Born se je raje lotil sicer jalovega študija prava, kmalu pa je kot vodilni habsburški prostozidar urejeval naravoslovno glasilo in vodil svobodomiselni del politike in znanosti monarhije. Ni samo na novo izumil južnoameriškega amalga-miranja, temveč je o njem organiziral in vodil kar prvo znanstveno konferenco, ki je zgolj do neke mere spominjala na sodobne dogodke te vrste. Kljub prijateljstvu s Podo in objavljanju številnih jezuitskih prispevkov v svo- jem prostozidarskem glasilu je Born postal zapriseženi norčujoči se sovrag jezuitov in še posebej dvornega astronoma M. Hella. V svoji razporeditvi meniških redov po Linnejevem vzorcu je medtem prepovedane jezuite resda izpustil, prostozidarski sobrat Mozart pa ga le ovekovečil v svoji Čarobni piščali. Podov sodelavec je bil tudi Franc Saleški Georg Eder (* 1738; f1788) s katerim sta leta 1776 na Terezijanišču sestavila seznam muzejskih fosilov. Eder je tam pravkar prevzel katedro za kemijo, metalurgijo in montanistiko, ki jo je obdržal ducat let vse do svoje smrti kot eden prvih profesorjev kemije v Habsburški monarhiji. Eder je svojo pedagoško pot začel leta 1763 in 1764 kot predavatelj gramatike v Ljubljani, tako da si lahko mislimo, da je obilico svojega kemijskega znanja zanesel tudi med Kranjce.14 Med poglavitne kemike nove dobe je spadal tudi Kranjec Frančišek pl. Muhlpacher (Millbacher, Muhlbacher, *1744; f1826). Kar dve leti je specializiral matematiko pri graškemu astronomu Aloisu Mayrju (* 1731). Družba za kmetijstvo in koristne umetnosti ga je takoj po prepovedi jezuitov leta 1774 poslala popisovati kranjske naravne danosti skupaj z B. Hacqueton in ljubljanskim profesorjem kmetijstva Johanom Giehlom. Žal pa kot prvi ljubljanski eksperimentalni fizik in kemik Muhlpacher nikakor ni mogel priti do ustrezne namestitve v Ljubljani ne kot jezuit, ne po prepovedi reda, čeravno se je nekaj časa uspešno udinjal v G. Gruberjevi navigacijski komisiji. Po aneksiji Galicije je poprosil za pomoč brata, ki je dobil tam visok položaj. Tako je F. Muhlpacher postal leta 1775/76 dolgoletni profesor kemije in vodja kemijskega laboratorija v Stanis3awowu, današnjem Ivano-Frankiv-sku v Ukrajini. Bil je prefekt gimnazije do upokojitve leta 1823, dne 16. 9. 1818 pa je postal častni kanonik pa ukazu cesarja.15 Tudi Frančiškov mlajši sobrat Joannes Christopho-rus Stelzhamer (Stelzhammer, * 1750; f1840) je specializiral matematiko pri graškemu astronomu Aloisu Mayrju. Rojen je bil na spodnjeavstrijskem gradu Weissenbach, ki ga je oskrboval njegov oče. Pri jezuitih je sledil zgledom svojega tri leta starejšega brata Paula. Prišel je v Ljubljano za predavatelja v prvem razredu; med ljubljanskimi srajcami je doživel dokaj blago prepoved jezuitov. Med letoma 1792-1797 je bil profesor fizike s kemijo v Celovcu, kjer je sodeloval s Sigmundom Hochenwartom s Kolovca pri Kamniku, poznejšim nadškofom Linza. Dunajskega matematika barona Metzburga in Boškovicevega prijatelja J. Liesganiga je spremljal pri geodetskih meritvah v poljski Galiciji do novembra 1796. Očitno se je dobro odrezal, saj je po obnovitvi Terezijanišča postal tam med letoma 1797-1825 profesor mineralogije in montanistike, nato pa še eksperimentalne fizike. Nadaljeval je z vodenjem laboratorija - muzeja po smrti avguštinca Andreasa Ksavierja Stutza (* 1747; f1806). Tam je samim presvetlim vojvodom kazal najnovejše kemijske poskuse tako prepričljivo, da je leta 1825 postal dekan dunajske filozofske fakultete in nato celo rektor. Med prvimi nekdanjimi jezuiti iz Av- Stanislav Južnič: Jezuitski kemiki v Habsburški monarhiji S70 Acta Chim. Slov. 2016, 63, (2), S65-S75 strijske province je svoje domislice objavljal v sodobnih znanstvenih glasilih. Med drugim je nova letala dunajskega urarja Jakoba Degena (* 1760; f1848) opisal v Gilber-tovih Analih16 še pred Degenovim slovitim poletom leta 1810, na Donavi pa je preizkušal prvi parnik potem ko je G. Gruber uspešno popravil poskuse na Muri. 7. Prodor novih teorij sestave snovi v obdonavski habsburški jezuitski prostor: Boškovic Medtem ko je nastajajoča poznobaročna kemija nezadržno polzela spod rok jezuitov v naročje novodobnih Preglednica 1: Podporniki sprva zelo uspešne Boškovicevega opisa točkaste neskončno deljive. Po njegovem dunajskem obisku (1757-1758) so si hitro večino pomembnih akademskih položajev v Habsburški monarhiji Ustanova Leto imenovanja Štefanovega podpornika Štefanov zagovornik Štefanov nasprotnik Dunajska Univerza 1857; 1863 Ettingshausen z zetom Grailichom; Stefan, Loschmidt Mach 1895-1898 Dunajska Politehnika 1816-1845 Študentje Johanna Philipa Neumanna Therezijanišče z Student Tivadar Puskäs, ki je pozneje zaposlil diplomatsko Akademijo N. Teslo v Budimpešti Akademija Dunaj 1863; 1865 Stefan Andreas von Baumgartner, Mach Univerza Gradec 1864-1865; 1869 Viktor von Lang; Ludwig Boltzmann, Klemenčič Mach (1865-1867), Simon Subic Gradec Politehnika 1865-1871 Ferdinand Lippich Štajerska naravoslov 1869 Boltzmann Subic na družba v Gradcu Buda Gimnazija Subic Buda Politehnika 1872 Kololman Szigeth Szily (Kälmän, * 1838; f1924) Univerza Pešta Student Otta Petzvala Loränd baron Eötwös Realka Pešta Subic, N. Teslov profesor Martin Sekulic Nemška Univerza v Pragi 1874- Lippich Mach 1867-1895 Praška Politehnika 1865- Schmidt Praška Kralovska Ceska 1864 Baumgartner spolecnost nauk Univerza Lvov 1862-1872 Alois Handl Univerza Czernovicz Alois Handl Univerza Innsbruck 1895 Ignac Klemenčič Realka Ljubljana 1870-1874 Joseph Finger Ljubljana Gimnazija, 1873 Luka Lavtar nato mariborsko učiteljišče Realka Maribor 1877 Robert Spiller Maribor Gimnazija 1891 Josef Hirschler Novo Mesto Gimnazija 1851-1884 Klemenčičev profesor Bernard Vovk Gorizia Gimnazija 1872-1907 Anton Santel Celovec Gimnazija 1845-1878; 1873-1783 Vincenc Borštner, profesor Josipa Plemlja Karl Robida Univerza Pavia, Zagovorniki pavijskega študenta Gabria Univerza Milano grofa Priola (1794-1850) Koper Gimnazija 1858-1863 Nicolo Vlacovich Zagreb Univerza 1874-1911 Nekdanji Machov praški asistent Vinko Dvoräk Mestna višja realka Trst 1863-1885 Nicolo Vlacovich Dresden Politehnika August Toepler 1876-1900 Energetik Georg Helm 1888-1919 in Tehniška visoka šola Leipzig Univerza Boltzmann 1900-1902 Wilhelm Ostwald Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji Acta Chim. Slov. 2016, 63, (2), S65-S75 S67 Jezuitske ideje od Chr.Gaviusa preko Athanasiuse Kircherja do ßoikovica Ideje zunaj jezuitskega reda of Keplerja do Newtons Graf 3: Spreminjanje fizikalnih idej poldrugih tisoč jezuitskih profesorjev matematike-fizike iz avstrijske in češke province po dekadah rojstva. Pomembnost profesorjev je ocenjena od 1 do 9 glede na pisana dela, pomembne katedre, važne službe in plemiški stan. Graf 4: Spreminjanje fizikalnih idej poldrugih tisoč jezuitskih profesorjev matematike in fizike iz avstrijske in češke province med katerimi jih je sto predavalo fiziko in matematiko tudi v Ljubljani glede na dekade njihovega rojstva. prostozidarskih učenjakov zvrsti nekdanjega jezuita Borna, je jezuitski labodji spev obrodil prodorno Boškovičevo teorijo neskončno deljive snovi sestavljene iz brez- dimenzijskih središč sil. Jezuit Boškovic je leta 1758 na Dunaju objavil svojo poglavitno knjigo in z njo v nekaj letih dobesedno pometel z vsemi nasprotniki in dvomljivci v Srednji Evropi. V Italiji in drugod nikakor ni bil tako uspešen, zato je z velikim olajšanjem sprejel katedro v tedaj habsburški Pavii. Seveda je bilo tudi pod habsburškim žezlom nekaj nasprotnikov, ki so Boškovicevi kemiji in fiziki kljubovali, med njimi predvsem, J. Stepling na Klementinumu Zlati Pragi in cesarski astronom doma iz Banske Stiavnice Maximilian Hell. Oba nasprotnika sta bila vsak po svoje vplivna. Kljub temu pa so bili njuni dvomi bolj kaplja v morje Boškovicevih občudovalcev, ki jih je prepoved jezuitskega reda sicer zavrla v vseevropski ekspanziji, nikakor pa jih ni onesposobila. Narodnostno in idejno mešana struktura Donavske monarhije pod habsburškim srednjeevropskim žezlom se je izkazala kot idealno okolje za tovrstne bliskovite spremembe v dojemanju kemijske strukture snovi. Seveda že itak nestrpni Boško-vic ni mogel biti povsem zadovoljen, saj so bile zgodnje Stanislav Južnič: Jezuitski kemiki v Habsburški monarhiji S72 Acta Chim. Slov. 2016, 63, (2), S65-S75 kritike njegove neskončno deljive snovi dovolj tehtne, da so to plat njegove kemije srednjeevropski učenjaki najraje izpustili, čeravno so sicer sledili Boškovicevemu nauku. Kot se pogosto zgodi, se je lastna teorija izmuznila Boškovicevi kontroli in zaživela lastno življenje podložno tudi spremembam, ki so bile Boškovicu zoprne, denimo tiste spod gosjega peresa soodkritelja kisika Josepha Priestleya na katere se je Boškovic ostro odzval tudi z nizkimi udarci s pritožbami pri Priestleyevem delodajalcu. Tako je tudi med kranjskimi frančiškani zelo vpliven Ka-stul Hieber (Castulus, * 1761 München; OFMobs 1780; t 18. 8. 1810 Ingolstadt) iz Chama severovzhodno od Re-gensburga izrecno nastopil proti Boškovicevi neskončni deljivosti snovi, čeravno je novomeški profesor matematike in grščine Teofil Zinsmeister (Franc, * 2. 11. 1777 Bavarska; OFM 10. 10. 1796; t 12. 11. 1817 Novo Mesto) pod Hieberjevim vplivom v svojem rokopisnem učbeniku navdušeno risal znamenito Boškovicevo krivuljo.17 Preglednica 2: Boškovicevi podporniki na ključnih akademskih položajih v Srednji Evropi Ustanova Leto prve Boškovicevi podporniki Boškovicevi katedre nasprotniki Boškovicevega podpornika Univerza Dunaj 1751- 1773 Joseph Xavier Liesganig, Scherffer (1751-1783); Piarist Johan Nepomuk Alber (7. 6. 1753 Mosonmagyarövär; t 7. 7. 1753 Pešta) Maximilan Hell, Remigio Döttler Terezijanišče 1754- Janez Schöttl (1754-1757; 1762-1763); Paul Mako (1757/1758-1774) Univerza Gradec 1763- -1804 Biwald (1755-1757 v Ljubljani); Leopold von Wisenfeldt 1771-1773 Univerza Buda 1765- Antun Radic (1765, 1766); Mako (1773-1782) Franz Weiss (1777-1785) Univerza Pešta Radic Univerza Praga Stanislus grof Wydra (-1804) Joseph Stepling (1748-1778) Univerza Lvov 1766- 1799 Scherffer (1773-1783); Ignjat Martinovic (1783-1791); Liesganig (1766-1799) Univerza Trnava 1761- 1777 Antun Radic (1763-1764): Ivan Horvat (Horväth, 1767-1773) Weiss (1761-1777) Univerza Innsbruck 1772- 1773 Franz Seraphin Zallinger Višji študiji Ljubljana 1760- Janez Schöttl (1759/60, 1760/61), Janez Krstnik Pogrietschnig (1763-1769), Gregor Schöttl (1768-1775) in njegovi študentje Franc Samuel Karpe ter Jurij Vega; Anton Ambschel (1773-1785) Maribor 1773- 1787 Janez Krstnik Kaschutnig Višji študiji Novo mesto 1803- 1816 Teofil Zinsmeister pod vplivom Kastula Hieberja Višji študiji Gorica 1761- Jožef Kauffmann (1761-1762, 1772-1773): Bernard Hohenwart (1769-1771); Jožef Jakob Liberatus Maffei pl. Glattfort (1771) Višji študiji Celovec 1759- Janez Schöttl (1758/59); Franc Ksaver Wulfen (1764-1805): Leopold baron Apfaltrer (1765-1773) Univerza Pavia, Univerza Milano 1763 Boškovic osebno Paolo Frisi, Louis Lagrange, Koprčan Gian Rinaldo grof Carli Višji študiji Trst in Rijeka 17671773- 1768, 1784 G. Schöttl, Franjo Orlando, Alois Capuano 1775-1782 1778-1793 predaval 1778-1810 Skotov podpornik Ambrozij Redeskini (Valentin Redeschini teologijo v Zagrebu; De Haidovio, Radeschini, * 21. 7. 1746 Ajdovščina; 1790-1804 apostolski OFMCap 1765; t 4. 2. 1810 Gorica) misijonar v Kraljevini Neapelj, 1808-1809 predaval teologijo pri Svetem Križu, predavatelj v Gorici.18 Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji Acta Chim. Slov. 2016, 63, (2), S65-S75 S67 8. Prodor novih kinetičnih teorij sestave snovi v obdonavski habsburški prostor Srednjeevropska jezikovno in duhovno mešana družba se je znova pokazala sprejemljivo za nove modele kemijske strukture snovi s kinetičnimi teorijami atomov koroškega Slovenca Jožefa Stefana in njegovega poglavitnega dijaka, soproga napol Slovenke Ludwiga Boltz-manna. Tudi to pot je smo bili priči praški izjemi Ernsta Macha, ki pa, kot vse izjeme, potrjuje pravilo, da se velike evropske ideje o kemijski strukturi snovi rade gojijo prav v izjemno heterogenem srednjeevropskem prostoru. Pozitivist Mach je svoje učence rad prav tako razpošiljal na pomembe položaje, vendar veliko manj uspešno od svojega nasprotnika Stefana. Stoletje potem ko je nastajajoča poznobaročna kemija nezadržno spolzela spod rok jezuitov v naročje sodobnejših znanstvenih mrež, se je Stefanu v borih nekaj letih posrečilo izpeljati podoben preobrat; le svojih starih študentskih nasprotnikov Ernsta Macha in Simona Subica ni uspel ne spreobrniti, ne povsem spodriniti. Novodobni kinetični atomizem dunajske šole v marsičem ni bil daleč od Boškovicevih točkastih središč sil in jim je pomagal najti prostor v sodobni kvantni mehaniki. Jezuitska ljubljanska dijaka Franc Samuel Karpe in Jurij Vega sta na vplivnih dunajskih katedrah zgladila pot za domala zvezen prehod od svojih Boškovicu naklonjenih učbenikov do kinetične teorije in statistične mehanike. Pomešani narodi in tradicije Srednje Evrope so edini zmogli domala zvezno udejanjiti obe spremembi, ki se v drugih okoljih, denimo pri Kelvino-vem navdušenju nad Boškovicem, kažejo bolj kot nenadni zasuki. Habsburško srednjeevropsko žezlo je bilo videti vsaj dvakrat izborno ozadje za spremembe v dojemanju kemijske strukture snovi. Ali bo še kdaj, to pot seveda brez cesarskega žezla? 9. Zaključek Becher in nekdanji jezuit Born sta vsak v svojem stoletju usmerjala baročne vpeljave nove znanosti imenovane kemija v habsburški prostor. Med njunima dobama je zijal prepad kot ločnica med alkimijo in industrij-sko-kmetijsko uporabo kemijskih dognanj. V habsburškem okolju so ta prepad premostili predvsem jezuiti odrasli ob rudarsko-industrijskih novodobnih naseljih spod Karpatov, med katere je spadal tudi Born. Čeravno slovenska rudarska naselja z Idrijo vred niso razvila tako pomembnih središč učenosti kot slovaška Banska Stiavnica, je napredek od Becherjeve dunajske terra pingus preko Stahlovega flogistona do sodobnejše La-voisierjeve kemije Jacquina, Pankla in B. Hacqueta v marsičem šel tudi skozi slovenska sita od Janeza Vajkar-da kneza Turjaškega, preko njegovega občudovalca in soimenjaka Valvasorja do poglavitnega ljubljanskega lastnika rudnikov barona Žige Zoisa, zasebnega dijaka jezuitov Gabrijela Gruberja in Maffeija. Medtem ko je nastajajoča poznobaročna kemija nezadržno polzela spod rok jezuitov v naročje novodobnih prostozidarjev vrste nekdanjega jezuita Borna, se je skozi jezuitski labodji spev skristalizirala mogočna Boškovičeva teorija neskončno deljive točkaste snovi, ki je v nekaj letih dobesedno preplavila Habsburški prostor z nekaj izjemami v J. Steplingovi zlati Pragi in M. Hellovem cesarskem Dunaju. Narodnostno in idejno mešana struktura Donavske monarhije pod habsburškim srednjeevropskim žezlom se je izkazala kot idealno okolje za tovrstne bliskovite spremembe v dojemanju kemijske strukture snovi, kar se je znova posrečilo stoletje pozneje s kinetičnimi teorijami atomov koroškega Slovenca Jožefa Stefana in njegovega poglavitnega dijaka, soproga napol Slovenke Ludwiga Boltzmanna. Tudi to pot je smo bili priči praški izjemi Ernsta Macha, ki pa, kot vse izjeme, potrjuje pravilo, da se velike evropske ideje o kemijski strukturi snovi rade gojijo prav v izjemno heterogenem srednjeevropskem prostoru. Summary Jesuits Chemists of Hapsburg Monarchy The achievements of the Jesuits from the Austrian and Bohemian provinces, who have published books on chemistry are focused. Their links with the area of today's Slovenia are particularly exposed. The guidelines which have enabled prompt victories of the ideas about the structure of matter of Jesuit Ruder Boškovic are indicated. Johann Joachim Becher and former Jesuit Ignaz von Born directed baroque introduction of a new science called chemistry in the Habsburg space each in his own century. Between their achievements there was a great intellectual gap as the dividing line between the alchemy and industrial-agricultural use of chemical knowledge. In the Habsburg environment, this gulf bridge was trespassed in particular with the Jesuits grown up with modern mining and industrial estates beneath the Carpathians, with the magnificent freemason Born as one of them in Transylvania. Although Slovenian mining town of Idrija did not develop such important center of learning such as Slovakian Banska Stiavnica, the progress of Becher's Viennese terra pingus through Georg Ernst Stahl's phlogiston to modern Lavoisier's chemistry of Jacquin, Pankl and B. Hacquet in many ways went through the sieve of the Slovenian magnates and masters of chemistry. The very first and best of them was Johann Weikhard Prince Auersperg, through his admirer and namesake Valvasor, until the Carniola Mine-Owner crystallographer baron Žiga Zois. It was no coincidence that Auersperg's confessors and home tutors were Jesuits of some fame. All formal Valvasor's studies were the Jesuit ones and Zois was a private student of Jesuits Stanislav Južnič: Jezuitski kemiki v Habsburški monarhiji S74 Acta Chim. Slov. 2016, 63, (2), S65-S75 Gabriel Gruber and Maffei. The inconceivable fast success of Boskovic's adherents in the Hapsburg monarchy of Zois' juvenile days is comparable with a similar rapid introduction of the kinetic theories of atoms of Slovene Jožef Stefan and Ludwig Boltzmann in the same geographical area a century later. Boltzmann was not only Stefan's best student, but he also married a half Slovenian maid. Even the exemptions which prove the rule were the same in both cases, the Prague Clementinum of Joseph Stepling and its descendant of positivist anti-atomist Ernst Mach. The national and with it also the spiritual mixture of Danube Monarchy under Habsburg Mid-European rule proved to be the ideal frame for such scientific blitzkriegs until the ill-famous Anschluss destroyed it for the generations to come. 10. Literatura 1. A. G. Debus, Alchemy and Early Modern Chemistry: Papers from Ambix, Jeremy Mills Publishing, 2004, str. 427; M. Baldwin, Alchemy and the Society of Jesus in the Seventeenth Century: Strange Bedfellows? Ambix, 1983, 40/2, str. 41. 2. Baldwin, 1983, str. 43. 3. Baldwin, 1983, str. 58. 4. T. Cevae, Philosophia novo-antiqua, Milano: Dominici Bel-lagattœ, 1718, str. 1, 14, 67, 90; L. Galler, Tractatus de Crea-tione mundi, Viennae, 1718, str. 2, 25, 28, 33, 66, 67, 70. 5. A. Gabon, Carmine Elegaico; Physica Exotica, seu Secreta naturae et artis, Trnava, 1717. 6. J. Franz, Dissertatio de natura electri, Viennae 1751; J.N. Stoeger, Scriptores Provinciae Austriacae Societatis Jesu ab ejus origine ad nostra usque tempora. Collectionis scripto-rum ejusdem Societatis universae. Viennae: Typis congrega-tionis Mechitharisticae. Tomus I—II, 1855, str. 86; C. Sommervogel, Bibliothèque de la Compagnie de Jésus, Première partie: Bibliographie par les Pères Augustin et Aloys de Backer, Nouvelle Édition par Carlos Sommervogel, S.J. Strasbourgeois, Tome I-IX. Bruxelles-Paris: Province de Belgique, 1890-1900, 3: 948-950. 7. J. Bartakovics, Metallurgicon seu de Culturafodinarum auri et argenti Libri II. Carmen cum Indiculo Vocabulorum Quo-rondum ad Aurariam Argentariamque spectantum Partes II. Trnava, 1748. 8. F. Ginthör, promocija Boskoviceve Dissertatio de inaequali-tate gravitatis in diversis terrae locis, Viennae 1751 (prva izdaja Rim 1741); F. Ginthör, promocija Boskoviceve Disser- tatio de viribus vivis... honoribus perillustris domini Caroli de Teuttern, dedicata, Viennae: Kaliwoda, 1752, skupaj z Franzem Gusmanomin jezuitom poznejšim rektorjem na Dunaju, Gradcu in Linzu Josephom Gundlom 1710-1770 (prva izdaja Rim 1745); Sommervogel, 1890-1900, 3: 1419; Stoeger, 1855, str. 98-99. 9. http://www.musiklexikon.ac.at/ml/musik_R/Reutter_ Familie.xml 10. J. Fridvalski, Mineralogia Magni Principartus Transilvani-ae, seu ejus metalla, semi metalla, supophura, salia, lapides et aquae, Cluj, 1767, str. 25, 102, 103, 105, 120, 132, 134137, 152, 174, 189. 11. J. Fridvalski, Dissertatio de Skumpia seu Cotino planta co-riaria cum diversis experimentis in M. principatu Transylvania institutis, Cluj, 1773, str. 23. 12. M. Pankl, Compendium Institutionum Physicarum I: Corpore abstracte II: De Corpore Chemice Considerato III: Physi-ce. Bratislava 1790, Adjustum et ad systema antiphlogisti-cum accomodatium, Bratislava, 1793, Buda 1797-1798; Matthaeus Pankl, Compendium Oeconomia Ruralis, Buda, 1790; 1793; 1797; I. Horváth, Elementae Physicae, 1790; C. Villeneuve, Rudolf Steiner: the British Connection: Elements from His Early Life, Temple Lodge Publishing, 2011, str. 365; J. Zemplén, The Reception of Copernicanism in Hungary, The Reception of Copernicus' heliocentric Theory - on the borders, (ur. J. Dobrzycki), 2013, str. 355. 13. N. Poda von Neuhaus, Berechnung der Luftmaschine, 1771; P.P. Aspaas, Maximilian Hell. Doktorat Tromsouit, 2012, str. 90. 14. F .S. G. Eder; N. Poda von Neuhaus, Syllabus Fossilium, Vienna, 1776; J.N. Stoeger, Scriptores Provinciae Austriacae Societatis Jesu ab ejus origine ad nostra usque tempora. Collectionis scriptorum ejusdem Societatis universae. Vien-nae: Typis congregationis Mechitharisticae. Tomus I—II, 1855, str. 69. 15. Lemberger Zeitung, 16.9.1818, prva stran. 16. Joannes Christophorus Stelzhamer, Ludwig Wilhelm Gilberts Annalen der Physik, 1808, 30; 1809, 31:. 17. C. Hieber, Theses selectiores ex philosophia. Pedemontium, 1799, str. 8; T. Zinsmeister, Tractatus ex Physica. Rokopis v Ljubljanski frančiškanski knjižnici 1 d 48, 1799; C. Hieber, Philosophia Corporum seu Physica: Pars i generalis ex variis / Novissimis Autoribus con gesta ac Systemate ordinata pro annis Praelectionibus P. Castuli Huber, Rokopis v Ljubljanski frančiškanski knjižnici 15 b 65, 1797. 18. V. Škafar, Knjige in knjižnica v nekdanjem kapucinskem samostanu v Mariboru (1613-1784). Časopis za zgodovino in narodopisje, 1993, 64/1: 81. Stanislav Južnič: Jezuitski kemiki v Habsbur{ki monarhiji Acta Chim. Slov. 2016, 63, (2), S65-S75 S67 Abstract The achievements of the Jesuits from the Austrian and Bohemian provinces, who have published books on chemistry are focused. Their links with the area of today's Slovenia are particularly exposed. The guidelines which have enabled prompt victories of the ideas about the structure of matter of Jesuit Ruder Boškovic are indicated. Inconceivable fast spread of Boškovic's adherents in the Hapsburg monarchy is compared with a similar rapid introduction of the kinetic theories of atoms of Slovene Jožef Stefan and Ludwig Boltzmann in the same geographical area. Boltzmann was not only Stefan's best student, but he also married a half Slovenian maid. Keywords: Jesuits, Hapsburg Monarchy, History of Chemistry, Ruder Boškovic, Jožef Stefan, Ludwig Boltzmann Stanislav Južnič: Jezuitski kemiki v Habsburški monarhiji S76 _Acta Chim. Slov. 2016, 63, (2), Supplement Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 77 POROČILO PREDSEDNIKA SLOVENSKEGA KEMIJSKEGA DRUŠTVA O DELU DRUŠTVA V LETU 2015 V letu 2015 je bilo dru{tvo aktivno na {tevilnih področjih. Morda smo bili {e vedno deležni pozitivnih vplivov mednarodnega leta kemije (leto 2011), 60-letnice ustanovitve Slovenskega kemijskega dru{tva (v letu 2011) in 60-letnice izdajanja dru{tvene revije Acta Chimica Slo-venica (v letu 2012). Prav tako pa se na žalost {e vedno čuti gospodarska, ekonomska in politična kriza v svetu in {e posebej v Sloveniji, vključno s krizo vrednot, kar seveda vpliva tudi na delovanje Slovenskega kemijskega dru{tva. V letu 2012 je bil ustanovljen častni odbor za pripravo slovesnosti ob obeležitvi 50. letnice smrti Prof. Maksa Samca (umrl v letu 1964), ki je poleg opravljanja drugih pomembnih funkcij (dekan Tehni{ke fakultete, rektor Univerze v Ljubljani, upravnik Kemijskega in{tituta) bil tudi soustanovitelj in prvi predsednik Slovenskega kemijskega dru{tva v letih od 1951 do 1963. Odbor je nadaljeval z delom v letih 2013, 2014 in 2015. Predlog odbora je bil, da bi na dan obletnice smrti (1. julij 2014) odkrili njegov doprsni kip. Ker so se pojavile nekatere organizacijske in tehnične težave, bomo doprsni kip odkrili v letu 2016. Ponosni pa smo na izid zbornika v njegov spomin. Zbornik je bil predstavljen na otvoritvi Slovenskih kemijskih dnevov v septembru 2015 v prisotnosti nekaterih sorodnikov prof. Maksa Samca in preko 100 udeležencev konference. Po mnenju {tevilnih bralcev je zbornik izjemno lepa publikacija, ki osvetljuje življenje in delo prof. Samca. Posebna zahvala gre dr. Tatjani Peterlin-Neumaier, pobudnici izdaje zbornika in ožjemu uredni{kemu odboru, ki mu je predsedoval akad. prof. dr. Branko Stanovnik. V njem so bili {e dr. Tatjana Peterlin-Neumaier, dr. Edvard Kobal in dr. Željko Oset. Zahvala gre tudi tehničnemu uredniku zbornika, g. Igorju Resniku, ki je opravil tako izvrstno delo in imel obilo potrpljenja z nami in na{imi muhami ter neskončnim {tevilom zahtevkov po dodatnem tekstu in popravkih. Slovenski kemijski dnevi so bili v letu 2015 prvič organizirani v Ljubljani, na novi Fakulteti za kemijo in kemijsko tehnologijo Univerze v Ljubljani, v skupni organizaciji Slovenskega kemijskega dru{tva in FKKT Univerze v Ljubljani, 24. in 25. septembra. Menim, da je Programski odbor, ki sem mu predsedoval, v njem pa so bili {e prof. Marija Be{ter Rogač, prof. Marjan Veber, prof. Janez Plavec in prof. Zdravko Kravanja, pripravil zanimivo in kvalitetno srečanje. Na posvetovanju je bilo predstavljeno več kot 140 prispevkov v obliki predavanj in posterjev. Delo je potekalo plenarno in v treh vzporednih sekcijah: • materiali, • vede o življenju ter • inženirstvo, tehnologije in drugo. Plenarni predavatelji so bili: prof. Werner Kunz, Univerza Regensburg, Nemčija; prof. Milena Horvat, Inštitut Jožef Stefan, Ljubljana; prof. Ivan Halazs, Inštitut Rudjer Boškovic, Zagreb; prof. Mojca Skerget, FKKT Univerze v Mariboru in Prof. Mariano Martin, Univerza v Salamanci, Španija. Poleg petih plenarnih predavanj so bila štiri »keynote« vabljena predavanja in dve promocijski predavanji iz industrije, Lotrič, d.o.o. in Mikro+Polo d.o.o. Posebej smo bili veseli treh študentskih predavanj. Predavanja so izbrali študenti iz t. im. »Cutting Edge« konference, ki je potekala dva dni prej, tudi na FKKT Univerze v Ljubljani. Profesor Peter Glavič je na okrogli mizi predstavil slovensko in evropsko tehnološko platformo SusChem in izvajanje njene nove strateške inovacijske in raziskovalne agende ter razpise za evropske projekte v letih 2016 in 2017. V letniku Acta Chimica Slovenica 2015(62) so izšle štiri številke s skupno 121 originalnimi znanstvenimi in strokovnimi prispevki na skupno 976 straneh z dvo-kolonskim tiskom. Druga številka je bila posvečena pokojnemu profesorju Juriju Brenčiču, tretja pa profesorju Jožetu Kollerju ob njegovi sedemdeseti obletnici. V uredništvo je prispelo preko 1200 prispevkov, od katerih jih na začetku zaradi neustrezne tehnične priprave in dokumentacije zavrnemo več kot 80 %. Pravilno oddani prispevki gredo v recenzentski postopek, od katerih pa v skladu z recenzentsko politiko sprejmemo le približno polovico prispevkov. Objavljeni članki pokrivajo aktualna področja organske, anorganske, fizikalne in analizne kemije, kemije materialov, kemijskega, biokemijskega in okoljskega inženirstva ter splošne, uporabne in biomedi-cinske kemije. Pisani so v angleškem jeziku s slovenskim povzetkom. V slovenskem delu revije - Društvenih vesteh, so bila na skupaj 139 straneh objavljena sekcijska poročila, ter seznam diplomskih, magistrskih in doktorskih del na širšem področju kemije v letu 2015 na slovenskih univerzah. V društvenih vesteh so bili objavljeni tudi slovenski strokovni prispevki o strukturi in zgodovini alkimije, profesorjih kemije Nikole Tesle, Valvazorjevih prispevkih h kemijski tehnologiji in jezuitski kemiji v Ljubljani. Faktor vpliva (Impact Factor) za Acta Chimica Slovenica za leto 2014 znaša 0,61 in je kljub prizadevnemu delu urednikov nižji od leto starejšega (IF = 0,81). Na internetu na strani http://acta.chem-soc.si objavljamo elektronsko verzijo Acta Chimica Slovenica, kar povečuje branost ter mednarodno odmevnost revije. Članki, objavljeni v ACSi, so povzeti še v Chemical Abstracts Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement Plus, Current Contents (Physical, Chemical and Earth Sciences), Science Citation Index Expanded in Scopus. Po enem letu ugotavljamo, da je bila uvedba OJS sistema izredno koristna. Na začetku 2015 leta smo uvedli tudi DOI sistem, ki bo v naslednjih letih povečal branost naše revije in s tem tudi Faktor vpliva. Od jeseni 2015 dalje uporabljamo tudi program za kontrolo plagiatorstva It-henticate, ki bo izboljšal kvaliteto objavljenih člankov. V letu 2016 načrtujemo izdajo štirih številk, od katerih bo predvidoma tretja posvečena pokojnemu profesorju in direktorju Kemijskega Inštituta Janku Jamniku. Konec leta 2014 in v začetku 2015 smo prenovili društveno domačo stran, ki je zdaj moderneje urejena in optimalno deluje na različnih napravah (računalniki, tab-lični računalniki, pametni telefoni). Upam, da vam bo všeč, predvsem pa je pomembno to, da so vse informacije (o društvu, o njegovih aktivnostih, o preteklih in bodočih dogodkih, vstopno mesto za revijo Acta Chimica Sloveni-ca, vstopno mesto za infomacije o Slovenskih kemijskih dnevih) dostopne na enem mestu, na domači strani društva. Nekaj informacij o financiranju izdajanja Acta Chimica Slovenica in na splošno o financah za delovanje društva. Nekaj let smo zbirali presežke v poslovnem skladu za "težke čase". Finančni obračun za leto 2015 na žalost kaže precej večje odhodke, kot prihodke, ki pa smo jih uspeli pokriti s sredstvi iz poslovnega sklada. Dvoletna pogodba o sofinanciranju izdajanja ACSi s strani ARRS za leti 2015 in 2016 je na letni ravni za več kot 9.000 EUR nižja od prejšnje letne pogodbene vrednosti (za leti 2013 in 2014). Nižja pogodbena vrednost je posledica zmanjšanja sredstev, ki jih država namenja za financiranje slovenske znanosti preko ARRS. Zahvaljujem se inštitucijam, ki finančno podpirajo njeno izdajanje (obe FKKT (Ljubljana in Maribor), Kemijski inštitut, Inštitut Jožef Stefan in Fakulteta za farmacijo Univerze v Ljubljani) Z objavo oglasa sta v letu 2015 od slovenskih podjetij pomagala Krka in Atotech Slovenija. Tudi Univerza v Novi Gorici nam je finančno pomagala z objavo oglasa. Največji finančni podpornik je država Slovenija preko dvoletne pogodbe o sofinanciranju. Kot povedano zgoraj, pa so se finančna sredstva precej zmanjšala. V aprilu 2015 je bilo Slovensko kemijsko društvo na letni skupščini, ki je potekala v Ljubljani, sprejeto v ECTNA - European Chemistry Thematic Network Association. Glavni odbor Slovenskega kemijskega društva je v decembru 2015 sprejel Akt o ustanovitvi Ustanove Janka Jamnika za iskrive mlade v znanosti, v spomin na cenjenega pokojnega direktorja Kemijskega inštituta profesorja Janka Jamnika. Prof. dr. Jamnik si je vseskozi prizadeval, da bi poklicno znanstveno in raziskovalno delo postalo privlačnejše za mlade. Zelo je podpiral vedoželjne mlade ljudi, jih znal spodbuditi, jim omogočil delo na Kemijskem inštitutu ter z njimi delil svoje bogato znanje in izkušnje. Temeljni namen Ustanove bo zato podpora mladim na njihovi raziskovalni poti. Člani Slovenskega kemijskega društva so bili v letu 2015 zelo dejavni tudi na področju mednarodnega sodelovanja. Poleg dvostranskega sodelovanja s kemijskimi društvi sosednjih in drugih srednjeevropskih držav, je bilo pomembno delovanje naših članov v mednarodnih združenjih IUPAC, EuCheMS, EFCE in EPF. Nekatere pomembne aktivnosti: 1. IUPAC generalna skupščina in IUPAC kongres sta v letu 2015 (avgust) potekala v Busanu v Južni Koreji. Generalne skupščine sta se udeležila Aleš Fajgelj (Division of Analytical Chemistry) in V. Kaučič (ChemRAWN Committee, IUPAC Council). 2. IUPAC CHEMRAWN XX (20th IUPAC Conference on Chemical Research Applied to World Needs, Herbal Medicine for Health Care in the 21st Century) je potekala v novembru 2015 v Daki, Bangladeš. 3. EuCheMS generalna skupščina je v septembru 2015 potekala na Dunaju, Avstrija. 4. ACHEMA 2015, 15. do 19. junij 2015, Frankfurt, Nemčija. 5. 21st International Symposium on Separation Sciences, 30. 6. do 3. 7. 2015, Ljubljana (organizirala dr. Irena Vovk s sodelavci). 6. 47. Mednarodna kemijska olimpijada je bila v juliju 2015 v Bakuju, Azerbajdžan. Slovenska ekipa je osvojila dve bronasti medalji, ki sta ju dobila Uroš Prešern (Gimnazija Novo mesto) in Jan Jelen (Gimnazija Bežigrad). Slovenijo sta zastopala še Klemen Kovač (Gimnazija Novo mesto) in Luka Pušnik (Gimnazija Ptuj). Mentorja ekipe sta bila dr. Andrej Godec in dr. Darko Dolenc, oba FKKT, Ljubljana. 7. ECM29 - 29. evropsko kristalografsko srečanje, avgust 2015, Rovinj, Hrvatska. Leto 2014 je bilo tudi mednarodno leto kristalografije. 8. Generalna skupščina EFCE je potekala 27. septembra 2015 v Nici, Francija, v sklopu več pomembnih konferenc s področja kemijskega inženirstva in kemijske tehnologije (10th European Congress of Chemical Engineering (ECCE10), 3rd European Congress of Applied Biotechnology (ECAB3), 5th EPIC European Process Intensification Conference (EPIC5), 15th Congress of the French Society of Chemical Engineering (SFGP)). 9. Srečanje avstrijskega kemijskega društva, 21. do 24. september 2015, Innsbruck, Avstrija. 10. 6. Hrvatsko-slovensko-srpski simpozij o zeolitih, 1. do. 3. 10. 2015, Sibenik, Hrvatska. V Ljubljani, 14. 3. 2016 Venčeslav Kaučič Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 79 Mariborska podružnica Mariborska podružnica se je v letu 2015 usmerila v izpolnitev ciljev, ki si jih je zastavila v preteklem letu. Člani mariborske podružnice smo se udeležili jubilejnih 21. slovenskih kemijskih dnevov, ki so potekali na Fakulteti za kemijo in kemijsko tehnologijo v Ljubljani. Predsedovali smo posameznim sekcijam in sodelovali kot predavatelji. Skrb Mariborske podružnice je tudi stalno izobraževanje članov. V ta namen smo organizirali strokovna predavanja in razne seminarje, na katerih so predavali priznani tuji in domači strokovnjaki. Predavanja so pokrivala pomembna področja teoretične in uporabne kemije, kemijske in procesne tehnike ter kemijskega izobraževanja. Aktivno smo sodelovali tudi pri mednarodnih poletnih šolah. Med drugim so se študenti in predavatelji, tako kot pretekla leta, udeležili že osme mednarodne poletne šole Measurement Science in Chemistry, ki je potekala v juliju v kraju Pulawy na Poljskem. Sodelovalo je devet evropskih univerz, članic konzorcija MSC Euromaster, pridružili pa so se tudi študenti iz drugih držav. Prizadevali smo si povečati število članov med študenti. Člani podružnice aktivno sodelujemo v raznih sekcijah Slovenskega kemijskega društva in tudi pri pripravi in izvedbi simpozijev in seminarjev, ki jih prireja Slovensko kemijsko društvo v sodelovanju z drugimi organizacijami. Darinka Brodnjak Vončina Komisije za slovensko kemijsko terminologijo in nomenklaturo v letu 2015 Komisija za slovensko kemijsko terminologijo in nomenklaturo je tudi v preteklem letu sodelovala pri delu Tehniške komisije Sekcije za terminološke slovarje pri Institutu za slovenski jezik ZRC SAZU. Člani tehniške komisije za področje kemije in kemijske tehnologije so Andrej Smalc in Leon Čelik iz ljubljanske ter Peter Glavič iz mariborske podružnice Slovenskega kemijskega društva. V letu 2015 se je nadaljevalo sodelovanje pri novi izdaji splošnega tehniškega slovarja, ki obsega tudi pripravljanje gradiva s področja kemije, kemijske tehnologije in kemijske tehnike. Kot je bilo omenjeno že v lanskoletnem poročilu, se po reorganizaciji od leta 2014 dalje delo opravlja dopisno, osnovno gradivo s pripombami članov pa se obravnava na rednih sejah po tri ure tedensko. V letu 2015 je bila dokončana obdelava gesel črke L, začela pa se je obravnava gesel črke M. Nadaljevalo se je tudi pripravljanje gradiva za predvideni slovar kemijske tehnike. Slovar bo obsegal pomem- bnejše pojme s tega področja in bo predstavljal pomembno dopolnitev splošnega tehniškega slovarja. Delo je zelo obsežno, saj z naglim razvojem vseh področij tehnike sproti narašča tudi število novih pojmov, ki jih je treba še terminološko obdelati. Slovar pripravlja ožja (štiričlanska) skupina članov širše Tehniške komisije na rednih sejah, ki so bile do leta 2014 enkrat tedensko, po reorganizaciji dela in ukinitvi financiranja s strani Inštituta za slovenski jezik pri ZRC SAZU v letu 2015 pa se komisija sestaja dvakrat mesečno po dve uri. Glavnina dela se zdaj opravi doma, na vsaki seji pa se obravnavajo le vnaprej pripravljena in obdelana gesla, njihovi popravki in dopolnitve pa se dokončno obravnavajo na naslednji seji ob pregledu zapisnika. Na ta način se je delo precej pospešilo, tako da je bilo v letu 2015 dokončno obdelano in vneseno v slovar razmeroma obsežno gradivo črk N, O, P in delno R. Skupaj je bilo v letu 2015 obdelanih 866 gesel. V letu 2015 so komisiji priskočili na pomoč Fakulteta za kemijo in kemijsko tehnologijo Univerze v Ljubljani, Fakulteta za kemijo in kemijsko tehnologijo Univerze v Mariboru, Tovarna zdravil Krka Novo mesto in Kemična tovarna Melamin Kočevje, s prispevki v skupnem znesku 2300 EUR. Zaradi pomanjkanja sredstev za delo poteka priprava slovarja kemije in kemijske tehnike praktično pro bono, saj smo mnenja, da bi bilo škoda prekiniti delo, ki je do praktično dveh tretjin že opravljeno - za dokončno slo-varopisno obdelavo je pripravljenih že okrog 7000 gesel. Poleg rednega dela v zvezi s slovarjem je komisija v preteklem letu strokovno pregledala še standard SIST ISO 80000-6 Veličine in enote - Elektromagnetizem (prav tako pro bono). Novi standard SIST ISO 80000 postopno nadomešča sedanji standard SIST ISO 31. Za leto 2016 je predvideno nadaljnje sodelovanje pri pripravi gradiva za novo izdajo Slovenskega tehniškega slovarja in nadaljnje zbiranje in obdelavo gradiva za novi slovar kemijske tehnike. Andrej Šmalc Poročilo o delu Sekcije mladih kemikov za leto 2015 V preteklem letu je ponovno zaživela Sekcija mladih kemikov (v nadaljevanju: SMK), ki trenutno šteje 53 članov. V letu 2015 je k sekciji pristopilo 29 novih članov, študentov UL FKKT, PeF, FE in MF ter UM FKKT. Sekcija mladih kemikov je namenjena študentom vseh treh stopenj in drugim strokovnjakom na področju kemije in sorodnih ved, do 35 let. V letu 2015 je SMK pristopila k EYCN (European Young Chemists' Network) pri EuChe-MS, v okviru znanstvene redakcije katerega člani SMK aktivno sodelujejo pri pripravi naslednjih evropskih projektov: Photocimica (evropsko tekmovanje v digitalni fotografiji na področju kemije), Project Management (spod- Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement bujanje in usmerjanje pri pravi projektov na področju kemije), Video Project (izdelava promocijskih video posnetkov za promocijo kemije v evropskem prostoru v okviru EuCheMS) in Video contest for pupils around Europe (evropsko tekmovanje mladih v videoposnetkih na področju kemije). Znotraj delovnih skupin SMK smo se člani srečevali dvakrat mesečno v prostorih Kemijskega inštituta in UL FKKT. Med glavnimi dejavnosti SMK je bila zlasti vzpostavitev povezave med študenti, mladimi doktorji, člani Slovenskega kemijskega društva, pedagoškimi delavci UL PeF in FKKT, raziskovalnimi inštituti v Sloveniji (Kemijski inštitut in Institut »Jožef Stefan«) ter podjetji, ki zaposlujejo kemike. Člani SMK spodbujamo študente in mlade kemike k raziskovalnemu delu, in da svoje delo tudi predstavijo na konferenci. V sklopu tega smo pričeli s sodelovanjem z Organizacijskim odborom Slovenskih kemijskih dni 2016 pri pripravi in organizaciji študentske sekcije na Slovenskih kemijskih dneh 2016, kjer bodo mladi dobili prvi stik z znanstvenim delom in stik s kolegi raziskovalci. V okviru SMK je ena izmed prednostnih nalog tudi promocija kemije in drugih naravoslovnih znanosti med učenci in dijaki slovenskih šol. Člani SMK smo v sodelovanju s Komisijo za kemijsko izobraževanje in posameznimi pedagoškimi delavci na Pedagoški fakulteti in Fakulteti za kemijo in kemijsko tehnologijo Univerze v Ljubljani pričeli z organizacijo Tekmovanja iz znanja kemije za priznanja Maksa Samca za šolsko leto 2017/2018, ki bo novost v slovenskem prostoru, saj bodo imeli učenci osmih in devetih razredov osnovnih šol poleg teoretičnega znanja imeli tudi možnost pokazati svoje eksperimentalne sposobnosti. V tem sklopu tega se člani SMK aktivno trudimo, da bi Slovensko kemijsko društvo pristopilo polnopravnim članom IJSO (International Junior Science Olympiad) in s tem tudi osnovnošolcem prvič omogočili, da zastopajo slovenske barve in pokažejo svoje znanje na mednarodnem nivoju. Člani SMK so aktivno sodelovali s člani Sekcije za spektroskopijo SKD v okviru ECTN (European Chemistry Thematic Network Association) pri analizi in prenosu evropskih testov za vrednotenje kemijskega znanja (eChemTest) na področju splošne kemije I (ob koncu osnovne šole) in II (ob koncu splošne gimnazije) na slovensko populacijo. Za Sekcijo mladih kemikov Ale{ Zupan~i~ Eurachem Slovenija - poročilo za leto 2015 V letu 2015 je bila Eurachem Slovenija aktivno vključena v dveh delovnih skupinah Eurachem-a: - Proficiency testing (Preverjanje usposobljenosti) -dr. Andreja Drolc (https://www.eurachem.org/index.php/euwgs/ptwg) - Education and training (Izobraževanje in usposabljanje) - dr. Nineta Majcen (https://www.eurachem.org/index.php/euwgs/etwg) V lanskem letu je dr. Andreja Drolc zaradi spremembe delovnega mesta in s tem povezanimi strokovnimi nalogami zaključila s članstvom v delovni skupini »Preverjanje usposobljenosti«. Za njen večletni prispevek ji je vodja delovne skupine v imenu vseh članov izrekel iskreno zahvalo. Predstavnik Slovenije v delovni skupini je sedaj Prof. Mitja Kolar. Na povabilo delovne skupine »Preverjanje usposobljenosti« je bila sprejeta odločitev, da bo naslednja delavnica »9th Proficiency testing in analytical chemistry, microbiology and laboratory medicine« potekala v Portorožu, 9.-12. oktober 2017 (http://eurachempt2017.eu). Dr. Nineta Hrastelj Majcen se je kot predstavnica Slovenije udeležila Generalne skupščine in sestanka delovne skupine »Izobraevanje in usposabljanje«, ki je bila 27.-28. maja 2015 v Varšavi, Poljska. V okviru delovne skupine »Izobraževanje in usposabljanje« med ostalim poteka revizija »Guide to Quality in Analytical Chemistry (2002)«, izdana pa je bila tudi krajsa brošura »You talk, we understand - The way out of the tower of Babel«. Informacije o delu Eurachem Slovenija in druge aktualnosti s področja zagotavljanja kakovosti na področju merjenj v kemiji in sorodnih ved so objavljene na http:// www.chem-soc.si/o-drustvu/podruznice-komisije-in -sekcije/sekcija-eurachem-slovenija. Nineta Hrastelj Majcen Vodja sekcije Eurachem Slovenija Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 81 KOLEDAR VAŽNEJŠIH ZNANSTVENIH SREČANJ S PODROČJA KEMIJE IN KEMIJSKE TEHNOLOGIJE SCIENTIFIC MEETINGS -CHEMISTRY AND CHEMICAL ENGINEERING July 2016 _ 2 - 7 Information: 3 - 6 Information: 3 - 8 Information: 3 - 8 Information: 3 - 8 Information: 3 - 8 Information: 6 - 8 Information: 10 - 14 Information: 10 - 14 Information: 10 - 15 Information: 12 - 15 Information: 16th INTERNATIONAL CONFERENCE ON THE CRYSTALLIZATION OF BIOLOGICAL MACROMOLECULES Prague, Czech Republic http://www.iccbml6.org/ ExTech'20l6 / ISSS'20l6 Torun, Poland http://www.extech-isss20l6.pl/ 23rd INTERNATIONAL CONFERENCE ON PHYSICAL ORGANIC CHEMISTRY (ICPOC-23) Sydney, Australia http://www.icpoc23.unsw.edu.au/ 16th CONFERENCE ON MOLTEN SALTS AND IONIC LIQUIDS Vienna, Austria http://www.euchem20l6.org/welcome/ 39th INTERNATIONAL CONFERENCE ON VACUUM ULTRAVIOLET AND X-RAY PHYSICS Zurich, Switzerland http://www.psi.ch/vuvx20l6 6th INTERNATIONAL CONFERENCE ON NANOSTRUCTURES AND NANOMATERIALS SELF-ASSEMBLY (NANOSEA) Giardini Naxos, Italy http://www.nanosea20l6.imm.cnr.it/ ChemCH20l6 - CHEMISTRY FOR CULTURAL HERITAGE 2016 Brussels, Belgium http://org.kikirpa.be/chemch20l6/ 80th PRAGUE MEETING ON MACROMOLECULES - SELF-ASSEMBLY IN THE WORLD OF POLYMERS (80PMM) Prague, Czech Republic www.imc.cas.cz/sympo/80pmm 14th INTERNATIONAL CONFERENCE ON SURFACE X-RAY AND NEUTRON SCATTERING (SXNS14) NY, United States https://www.bnl.gov/sxnsl4/ 18th INTERNATIONAL CONFERENCE ON METAL ORGANIC VAPOR PHASE EPITAXY (ICMOVPE-XVIII) San Diego, CA, United States www.mrs.org/icmovpe-xviii 13th EUROPEAN WORKSHOP ON LASER ABLATION Ljubljana, Slovenia http://ewla20l6.ki.si/ Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement 17 - 21 IUPAC WORLD POLYMER CONGRESS (MACRO 2016) Istanbul, Turkey Information: www.macro2016.org 17 - 22 28th INTERNATIONAL CARBOHYDRATE SYMPOSIUM New Orleans, Louisiana, USA Information: http://ics.sites.acs.org 24 - 29 INTERNATIONAL SYMPOSIUM ON SOLUBILITY PHENOMENA AND RELATED EQUILIBRIUM PROCESSES (ISSP17) Geneva, Switzerland Information: http://issp17.unige.ch/ 25 - 27 7th INTERNATIONAL CONFERENCE ON ADVANCED NANOMATERIALS (ANM2016) Aveiro, Portugal Information: http://www.anm2016.com/ August 2016 6 - 9 Information: 7 - 10 Information: 7 - 12 Information: 7 - 12 Information: 15 - 20 Information: 21 - 26 Information: 24 - 26 Information: 28 - 31 Information: 28 - Sept. 1 Information: 28 - Sept. 2 Information: 1ST INTERNATIONAL CONFERENCE ON CHEMICAL SCIENCES & APPLICATIONS Alexandria, Egypt http://icpam-01.naturalspublishing.com/index.asp 10th INTERNATIONAL DRYING SYMPOSIUM Gifu, Japan http://www.efce.info/IDS+2016.html 15th INTERNATIONAL SYMPOSIUM ON METAL-HYDROGEN SYSTEMS Interlaken, Switzerland https://mh2016.ch/ 18th INTERNATIONAL CONFERENCE ON CRYSTAL GROWTH AND EPITAXY ICCGE-18 Nagoya, Japan http://www.iccge18.jp/ 24th IUPAC INTERNATIONAL CONFERENCE ON CHEMISTRY EDUCATION (ICCE2016) Kuching, Malaysia www.icce2016.org.my 67th ANNUAL MEETING OF THE INTERNATIONAL SOCIETY OF ELECTROCHEMISTRY The Hague, The Netherlands http://www.ise-online.org/annmeet/next_meetings.php 16th NORDIC FILTRATION SYMPOSIUM Lappeenranta, Finland http://www.lut.fi/web/en/nordic-filtration-symposium-2016 CHISA 2016 AND PRES 2016 Prague, Czech Republic http://www.chisa.cz/2016/ 30th MEETING OF THE EUROPEAN CRYSTALLOGRAPHIC ASSOCIATION Basel, Switzerland http://ecm30.ecanews.org/2016.html EMC2016 - EUROPEAN MICROSCOPY CONGRESS Lyon, France http://emc2016.fr/en/ Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement_ 533 29 - Sept. 2 NRC9 - 9th INTERNATIONAL CONFERENCE ON NUCLEAR AND RADIOCHEMISTRY Helsinki, Finland Information: http://nrc9.it.helsinki.fi/ 31 - Sept. 3 CHEMICAL BIOLOGY 2016 Heidelberg, Germany Information: http://www.embl.de/training/events/2016/CHB1601/ speakers_gallery/index.html September 2016 4 - 7 Information: 4 - 8 Information: 4 - 8 Information: 4 - 8 Information: 4 - 8 Information: 4 - 9 Information: 7 - 10 Information: 11 - 14 Information: 11 - 15 Information: 11 - 15 Information: 11 - 15 Information: 11 - 15 Information: 12 - 16 Information: 23rd CONFERENCE OF ISOPRENOIDS Minsk, Republic of Belarus http://isoprenoids-23.basnet.by/ 21st EuroQSAR - 21st EUROPEAN SYMPOSIUM ON QUANTITATIVE STRUCTURE-ACTIVITY RELATIONSHIP Verona, Italy www.euroqsar2016.org 6th INTERNATIONAL IUPAC CONFERENCE ON GREEN CHEMISTRY Venice, Italy www.greeniupac2016.eu 15th INTERNATIONAL CONFERENCE ON MOLECULE-BASED MAGNETS Sendai, Japan http://www.icmm2016.imr.tohoku.ac.jp/ 9th AES 2016 - 9th ASIAN-EUROPEAN SYMPOSIUM ON METAL-MEDIATED EFFICIENT ORGANIC SYNTHESIS Stockholm, Sweden http://aes2016.se/ THE 16th INTERNATIONAL CONFERENCE ON LIQUID AND AMORPHOUS METALS (LAM-16) Bonn - Bad Godesberg, Germany https://dlr-mp.meetingmasters.de/LAM16 ECRICE - EUROPEAN CONFERENCE ON RESEARCH IN CHEMICAL EDUCATION Barcelona, Spain http://ecrice2016.com/ EUROPEAN SYMPOSIUM ON BIOCHEMICAL ENGINEERING SCIENCES, BIOENERGY AND BIOMOLECULES Dublin, Ireland http://www.esbes2016.org/ 6th EuCheMS CHEMISTRY CONGRESS Seville, Spain http://www.euchems-seville2016.org/ 5th INTERNATIONAL CONFERENCE ON METAL-ORGANIC FRAMEWORKS & OPEN FRAMEWORK COMPOUNDS (MOF 2016) Long Beach, CA, United States www.mrs.org/mof-2016 EUROPEAN CORROSION CONGRESS Montpellier, France http://www.eurocorr.org/eurocorr2016.html INTERNATIONAL BEAM INSTRUMENTATION CONFERENCE IBIC 2016 Barcelona, Spain http://www.ibic2016.org/ BloodSurf2016 Wellesley, MA, USA www.ireviakine.net/Bloodsurf2016 Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement 18 - 23 Information: 19 - 23 Information: 21 - 23 Information: 21 - 25 Information: 24 - 27 Information: 25 - 28 Information: 25 - 28 Information: 26 - 30 Information: SOLID STATE CHEMISTRY CONFERENCE (SSC 2016) Prague, Czech Republic http://www.ssc-conference.com/home XXII INTERNATIONAL CONFERENCE ON CHEMICAL REACTORS London, United Kingdom http://conf.nsc.ru/CR_22/en 16th RUZICKA DAYS - INTERNATIONAL CONFERENCE 16th RUZICKA DAYS: »TODAY SCIENCE - TOMORROW INDUSTRY« Vukovar, Croatia http://www.euchems.eu/events/16th-ruzicka-days-international-conference-16th-ruzicka-days -today-science-tomorrow-industry/ 24th CROATIAN-SLOVENIAN CRYSTALLOGRAPHIC MEETING (CSCM24) Bol, Croatia http://cscm24.org 29th INTERNATIONAL SYMPOSIUM ON THE CHEMISTRY OF NATURAL PRODUCTS AND THE 9th INTERNATIONAL CONFERENCE ON BIODIVERSITY (ISCNP-29 & ICOB-9) Izmir, Turkey http://www.iscnp29-icob9.org/ CISAP-7 - 7th INTERNATIONAL CONFERENCE ON SAFETY & ENVIRONMENT IN PROCESS & POWER INDUSTRY Ischia, Italy http://www.aidic.it/cisap7/ CHEMECA 2016 Adelaide, Australia http://www.chemeca2016.org/ XX MENDELEEV CONGRESS ON GENERAL AND APPLIED CHEMISTRY Ekaterinburg, Sverdlovsk region, Russia https://mendeleev2016.uran.ru/ October 2016 4 - 7 Information: 9 - 12 Information: 9 - 12 Information: 12 - 14 Information: 14 - 19 Information: 16 - 19 Information: IUPAC-PSK40 CONFERENCE ON ADVANCED POLYMERIC MATERIALS Jeju, South Korea www.psk40.orgs XXVII INTERAMERICAN CONGRESS OF CHEMICAL ENGINEERING Cuzco City, Peru http://ciiq.pe/ SPICA 2016 - 16th INTERNATIONAL SYMPOSIUM ON PREPARATIVE AND INDUSTRIAL CHROMATOGRAPHY AND ALLIED TECHNIQUES Vienna, Austria www.spica2016.org 2nd INTERNATIONAL EPNOE JUNIOR SCIENTISTS MEETING Sophia-Antipolis, France http://chem-soc.si/novice/2nd-international-epnoe-junior-scientists-meeting 12th IUPAC INTERNATIONAL CONFERENCE ON NOVEL MATERIALS AND THEIR SYNTHESIS (NMS-XII) Changsha, China http://www.nms-iupac.org/present/ 3rd INTERNATIONAL CONFERENCE ON BIOINSPIRED AND BIOBASED CHEMISTRY & MATERIALS Nice, France http://www.nice2016-conference.com Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 85 16 - 19 Information: 17 - 19 Information: 24 - 26 Information: 24 - 26 Information: CSChE 2016 - 66th CANADIAN CHEMICAL ENGINEERING CONFERENCE Quebec, Canada http://www.csche2016.ca/ INTERNATIONAL CONFERENCE ON APPLIED CRYSTALLOGRAPHY Houston, United States http://www.iucr.org/calendar/events/topics/general/international-conference-on-applied-crystallography 17th INTERNATIONAL BIOTECHNOLOGY SYMPOSIUM AND EXHIBITION (IBS 2016) Melbourne, Australia www.ibs2016.org CHEMICAL RESEARCH IN FLANDERS - CRF Blankenberge, Belgium http://www.efce.info/Chemical+Research+in+Flanders+_+CRF-p-20000670.html November 2016 8 - 10 Information: TeQ - CHEMICAL AND PROCESS TECHNOLOGY 2016 Rio de Janeiro, Brazil http://tecnologiaquimica.com.br/en/ December 2016 11 - 16 Information: 21st IUPAC INTERNATIONAL CONFERENCE ON ORGANIC SYNTHESIS (ICOS 21) Mumbai, India www.chem.iitb.ac.in/icos21/ 2017 April 2017 10 - 13 Information: 19 - 22 Information: ELECTROSTATICS 2017 Frankfurt am Main, Germany http://www.dechema.de/en/electrostatics2017.html 25th CROATIAN MEETING OF CHEMISTS AND CHEMICAL ENGINEERS Porec, Croatia http://25hskiki.org/en/homepage/ May 2017 _ 7 - 11 Information: 23 - 25 Information: 25 - 27 Information: SETAC EUROPE 27th ANNUAL MEETING Brussels, Belgium http://www.setac.org/events/EventDetails.aspx?id=683532&group= 14th JOINT EUROPEAN THERMODYNAMICS CONFERENCE 2017 Budapest, Hungary http://jetc2017.hu/ MaCKiE-2017 - INTERNATIONAL CONFERENCE ON MATHEMATICS IN CHEMICAL KINETICS AND ENGINEERING (MaCKiE) Budapest, Hungary http://www.mackie-workshops.com/ June 13 - 15 V INTERNATIONAL SYMPOSIUM ON RELIABLE FLOW OF PARTICULATE SOLIDS Skien, Norway Information: http://www.relpowflo.no/ Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement 18 - 22 Information: 19 - 21 Information: ICCE 2017 - 16th EUCHEMS INTERNATIONAL CONFERENCE ON CHEMISTRY AND THE ENVIRONMENT Oslo, Norway http://www.icce2017.org/ 6th EUROPEAN DRYING CONFERENCE Liège, Belgium http://efce.info/EuroDrying+2017.html July 2017 2 - 5 Information: 2 - 6 Information: 2 - 7 Information: 7 - 10 Information: 9 - 14 Information: 4th EUCHEMS INORGANIC CHEMISTRY CONFERENCE - EICC-4 Copenhagen, Denmark http://www.euchems.eu/events/4th-euchems-inorganic-chemistry-conference-eicc-4/ INTERNATIONAL SYMPOSIUM ON MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY IN CONJUNCTION WITH ISACS: CHALLENGES IN ORGANIC MATERIALS & SUPRAMOLECULAR CHEMISTRY Cambridge, United Kingdom http://www.rsc.org/events/detail/17933/international-symposium-on-macrocyclic-and- supramolecular-chemistry-in-conjunction-with-isacs-challenges-in-organic-materials-and- supramolecular-chemistry 16th EUROPEAN POLYMER CONGRESS Lyon, France http://www.europolyfed.org/home 10th INTERNATIONAL SYMPOSIUM ON CATALYSIS IN MULTIPHASE REACTORS (CAMURE-10) & 9th INTERNATIONAL SYMPOSIUM ON MULTIFUNCTIONAL REACTORS (ISMR-9) Tsingtao (Qingdao), PR China http://camure2017.csp.escience.cn/dct/page/! 46th IUPAC WORLD CHEMISTRY CONGRESS (IUPAC-2017) Sao Paulo, Brazil www.IUPAC2017.org August 2017 13 - 17 Information: 20 - 23 Information: September 2017 3 - 6 Information: 3 - 8 Information: SE2017 - 200 YEARS OF SELENIUM RESEARCH Stockholm, Sweden http://se2017.se/ GLS-13 - 13th INTERNATIONAL CONFERENCE ON GAS-LIQUID AND GAS-LIQUID-SOLID REACTOR ENGINEERING (GLS-13) Brussels, Belgium http://www.gls13.com/ 3rd EuGSC - 3rd EuCheMS CONGRESS ON GREEN AND SUSTAINABLE CHEMISTRY York, UK http://www.euchems.eu/events/3rd-eugsc-3rd-euchems-congress-on-green-adn-sustainable -chemistry/ 21st EUROPEAN CONFERENCE ON THERMOPHYSICAL PROPERTIES Graz, Austria http://ectp2017.tugraz.at/ Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 87 October 2017 1 - 5 Information: 1 - 5 Information: 1 - 5 Information: EPIC 2017 - 6th EUROPEAN PROCESS INTENSIFICATION CONFERENCE 2017 Barcelona, Spain http://www.wcce10.org/index.php/en/ WCCE10 - 10th WORLD CONGRESS OF CHEMICAL ENGINEERING INCORPORATING THE 11th EUROPEAN CONGRESS OF CHEMICAL ENGINEERING (ECCE11) Barcelona, Spain http://www.wcce10.org/index.php/en/ 4th EUROPEAN CONGRESS OF APPLIED BIOTECHNOLOGY - ECAB3 Barcelona, Spain http://www.wcce10.org/index.php/en/ November HPLC 2017 - THE 46th INTERNATIONAL SYMPOSIUM ON HIGH PERFORMANCE LIQUID PHASE SEPARATIONS AND RELATED TECHNIQUES Jeju Island, Republic Of Korea http://www.hplc2017-jeju.org 5 - 9 Information: Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement Acta Chimica Slovenica Author Guidelines Submissions Submission to ACSi is made with the implicit understanding that neither the manuscript nor the essence of its content has been published in whole or in part and that it is not being considered for publication elsewhere. All the listed authors should have agreed on the content and the corresponding (submitting) author is responsible for having ensured that this agreement has been reached. The acceptance of an article is based entirely on its scientific merit, as judged by peer review. There are no page charges for publishing articles in ACSi. Submission material Typical submission consists of: • full manuscript (Word file, with title, authors, abstract, keywords, figures and tables embedded, and references); • supplementary files: - Statement of novelty (Word file), - List of suggested reviewers (Word file), - ZIP file containing graphics (figures, illustrations, images, photographs), - Graphical abstract (single graphics file), - Proposed cover picture (optional, single graphics file), - Appendices (optional, Word files, graphics files). Submission process Submission process consists of 5 steps. Before submission, authors should go through the checklist at the bottom of these guidelines page and prepare for submission: Step 1: Starting the submission • Choose one of the journal sections. • Confirm all the requirements of the checklist. • Additional plain text comments for the editor can be provided in the relevant text field. Step 2: Upload submission • Upload full manuscript in the form of a Word file (with title, authors, abstract, keywords, figures and tables embedded, and references). Step 3: Enter metadata • First name, last name, contact email and affiliation for all authors, in relevant order, must be provided. Corresponding author has to be selected. Full postal address and phone number of the corresponding author has to be provided. • Title and abstract must be provided in plain text. • Keywords must be provided (max. 6, separated by semicolons). • Data about contributors and supporting agencies may be entered. • References in plain text must be provided in the relevant text filed. Step 4: Upload supplementary files • Statement of novelty in a Word file must be uploaded • List of suggested reviewers with at least three reviewers must be uploaded as a Word file. • All graphics have to be uploaded in a single ZIP file. Graphics should be named Figure 1.jpg, Figure 2.eps, etc. • Graphical abstract image must be uploaded separately. • Proposed cover picture (optional) should be uploaded separately. • Any additional appendices (optional) to the paper may be uploaded. Appendices may be published as a supplementary material to the paper, if accepted. • For each uploaded file the author is asked for additional metadata which may be provided. Depending of the type of the file please provide the relevant title (Statement of novelty, List of suggested reviewers, Figures, Graphical abstract, Proposed cover picture, Appendix). Step 5: Confirmation • Final confirmation is required. Article Types Review articles are welcome in any area of chemistry and may cover a wider or a more specialized area, if a high impact is expected. Manuscripts normally should not exceed 40 pages of one column format (letter size 12, 33 lines per page). Authors should consult the ACSi editor prior to preparation of a review article. Scientific articles should have the following structure: 1. Title (max. 150 characters), 2. Authors and affiliations, 3. Abstract (max. 1000 characters), 4. Keywords (max. 6), 5. Introduction, 6. Experimental (Results and Discussion), 7. Results and Discussion (Experimental), 8. Conclusions, 9. Acknowledgements (if any), 10. References. The sections should be arranged in the sequence generally accepted for publications in the respective fields. Scientific articles should report significant Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 89 and innovative achievements and exhibit a high level of originality. Short communications generally follow the same order of sections, but should be short (max. 2500 words) and report a significant aspect of research work meriting separate publication. Technical articles report applications of an already described innovation. Typically, technical articles are not based on new experiments. Preparation of Submissions Text of the submitted articles must be prepared with Word for Windows. Normal style set to single column, 1.5 line spacing, and 12 pt Times New Roman font is recommended. Line numbering (continuous, for the whole document) must be enabled to simplify the reviewing process. For any other format, please consult the editor. Articles should be written preferably in English. Correct spelling and grammar are the sole responsibility of the aut-hor(s). Papers should be written in a concise and succinct manner. Graphics (figures, graphs, illustrations, digital images, photographs) should be inserted in the text where appropriate. The captions should be self-explanatory. Lettering should be readable (suggested 8 point Arial font) with equal size in all figures. Use common programs such as Word Excel to prepare figures (graphs) and ChemDraw to prepare structures in their final size (8 cm for single column width or 17 cm for double column width) so that neither reduction nor enlargement is required. In graphs, only the graph area determined by both axes should be in the frame, while a frame around the whole graph should be omitted. The graph area should be white. The legend should be inside the graph area. The style of all graphs should be the same. Figures and illustrations should be of sufficient quality for the printed version, i.e. 300 dpi minimum. Digital images and photographs should be of high quality (minimum 250 dpi resolution). On submission, figures should be of good enough resolution to be assessed by the referees, ideally as JPEGs. High-resolution figures (in JPEG, TIFF, or EPS format) might be required if the paper is accepted for publication. Tables should be prepared in the Word file of the paper as usual Word tables. The captions should above the table and self-explanatory. References should be numbered and ordered sequentially as they appear in the text, likewiise methods, tables, figure captions. When cited in the text, reference numbers should be superscripted, following punctuation marks. It is the sole responsibility of authors to cite articles that have been submitted to a journal or were in print at the time of submission to ACSi. Formatting of references to published work should follow the journal style; please also consult a recent issue: 1. J. W. Smith, A. G. White, Acta Chim. Slov. 2008, 55, 1055-1059. 2. M. F. Kemmere, T. F. Keurentjes, in: S. P. Nunes, K. V. Peinemann (Ed.): Membrane Technology in the Chemical Industry, Wiley-VCH, Weinheim, Germany, 2008, pp. 229-255. 3. J. Levec, Arrangement and process for oxidizing an aqueous medium, US Patent Number 5,928,521, date of patent July 27, 1999. 4. L. A. Bursill, J. M. Thomas, in: R. Sersale, C. Col-lela, R. Aiello (Eds.), Recent Progress Report and Discussions: 5th International Zeolite Conference, Naples, Italy, 1980, Gianini, Naples, 1981, pp. 25-30. 5. J. Szegezdi, F. Csizmadia, Prediction of dissociation constant using microconstants, http://www. chemaxon.com/conf/Prediction_of_dissociation _constant_using_microco nstants.pdf, (assessed: March 31, 2008) Titles of journals shoud be abbreviated according to Chemical Abstracts Service Source Index (CAS- SI). Special Notes • Complete characterization, including crystal structure, should be given when the synthesis of new compounds in crystal form is reported. • Numerical data should be reported with the number of significant digits corresponding to the magnitude of experimental uncertainty. • The SI system of units and IUPAC recommendations for nomenclature, symbols and abbreviations should be followed closely. Additionally, the authors should follow the general guidelines when citing spectral and analytical data, and depositing crystallographic data. • Characters should be correctly represented throughout the manuscript: for example, 1 (one) and l (ell), 0 (zero) and O (oh), x (ex), D7 (times sign), B0 (degree sign). Use Symbol font for all Greek letters and mathematical symbols. • The rules and recommendations of the IUBMB and the International Union of Pure and Applied Chemistry (IUPAC) should be used for abbreviation of chemical names, nomenclature of chemical compounds, enzyme nomenclature, isotopic compounds, optically active isomers, and spectroscopic data. • A conflict of interest occurs when an individual (author, reviewer, editor) or its organization is involved in multiple interests, one of which could possibly corrupt the motivation for an act in the other. Financial relationships are the most easily identifiable conflicts of interest, while conflicts can occur also as personal relationships, academic competition, etc. The Editors will make effort to ensure that conflicts of interest will not compromise the evaluation process; potential editors and reviewers will be Dru{tvene vesti in druge aktualnosti S78 Acta Chim. Slov. 2016, 63, (2), Supplement asked to exempt themselves from review process when such conflict of interest exists. When the manuscript is submitted for publication, the authors are expected to disclose any relationships that might pose potential conflict of interest with respect to results reported in that manuscript. In the Acknowledgement section the source of funding support should be mentioned. The statement of disclosure must be provided as Comments to Editor during the submission process. • Published statement of Informed Consent. Research described in papers submitted to ACSi must adhere to the principles of the Declaration of Helsinki (http://www.wma.net/ e/policy/b3.htm). These studies must be approved by an appropriate institutional review board or committee, and informed consent must be obtained from subjects. The Methods section of the paper must include: 1) a statement of protocol approval from an institutional review board or committee and 2), a statement that informed consent was obtained from the human subjects or their representatives. • Published Statement of Human and Animal Rights. When reporting experiments on human subjects, authors should indicate whether the procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008. If doubt exists whether the research was conducted in accordance with the Helsinki Declaration, the authors must explain the rationale for their approach and demonstrate that the institutional review body explicitly approved the doubtful aspects of the study. When reporting experiments on animals, authors should indicate whether the institutional and national guide for the care and use of laboratory animals was followed. • Contributions authored by Slovenian scientists are evaluated by non-Slovenian referees. • Papers describing microwave-assisted reactions performed in domestic microwave ovens are not considered for publication in Acta Chimi-ca Slovenica. • Manuscripts that are not prepared and submitted in accord with the instructions for authors are not considered for publication. Appendices Authors are encouraged to make use of supporting information for publication, which is supplementary material (appendices) that is submitted at the same time as the manuscript. It is made available on the Journal's web site and is linked to the article in the Journal's Web edition. The use of supporting information is particularly appropriate for presenting additional graphs, spectra, tables and discussion and is more likely to be of interest to specialists than to general readers. When preparing supporting information, authors should keep in mind that the supporting information files will not be edited by the editorial staff. In addition, the files should be not too large (upper limit 10 MB) and should be provided in common widely known file formats so as to be accessible to readers without difficulty. All files of supplementary materials are loaded separatly during the submission process as supplementary files. Proposed Cover Picture and Graphical Abstract Image Authors are encouraged to submit illustrations as candidates for the journal Cover Picture as well as graphical abstracts. Graphical abstract contains an image that appears as a part of the entry in the table of contents in both online and printed edition. The pictures may be the same. The illustrations must be related to the subject matter of the paper. Usually both proposed cover picture and picture for graphical abstract are the same, but authors may provide different pictures as well. Graphical content: an ideally full-colour illustration of resolution 300 dpi from the manuscript must be proposed with the submission. Graphical abstract pictures are printed in size 6.5 x 4 cm (hence minimal resolution of 770 x 470 pixels). Cover picture is printed in size 11 x 9.5 cm (hence minimal resolution of 1300 x 1130 pixels). Statement of novelty Statement of novelty is provided in a Word file and submitted as a supplementary file in step 4 of submission process. Authors should in no more then 100 words emphasize the scientific novelty of the presented research. Do not repeat for this purpose the content of your abstract. List of suggested reviewers List of suggested reviewers is a Word file submitted as a supplementary file in step 4 of submission process. Authors should propose the names, full affiliation (department, institution, city and country) and e-mail addresses of three potential referees. For each reviewer at least one reference relevant to the scientific field should be provided as well. Appropriate referees should be knowledgeable about the subject but have no close connection with any of the authors. In addition, referees should be from institutions other than (and preferably countries other than) those of any of the authors. How to Submit Users registred in the role of author can start submission by choosing USER HOME link on the top of the page, then choosing the role of the Author and follow the relevant link for start of submission. Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 91 Prior to submission we strongly recommend that you familiarize yourself with ACSi style by browsing the journal, either in print or online, particularly if you have not submitted to the ACSi before or recently. Correspondence All correspondence with the ACSi editor regarding the paper goes through this web site and emails. Emails are sent and recorded in the web site database. All emails you receive from the system contain relevant links. Please do not answer the emails directly but use the embedded links in the emails for carrying out relevant actions. Alternatively, you can carry out all the actions and correspondence through the online system by logging in and selecting relevant options. Proofs Proofs will be dispatched via e-mail and corrections should be returned to the editor by e-mail as quickly as possible, normally within 48 hours of receipt. Typing errors should be corrected; other changes of contents will be treated as new submissions. Submission Preparation Checklist As part of the submission process, authors are required to check off their submission's compliance with all of the following items, and submissions may be returned to authors that do not adhere to these guidelines. 1. The submission has not been previously published, nor is it under consideration for publication in any other journal (or an explanation has been provided in Comments to the Editor). 2. All the listed authors have agreed on the content and the corresponding (submitting) author is responsible for having ensured that this agreement has been reached. 3. The submission files are in the correct format: manuscript in MS Word; diagrams and graphs are created in Excel and saved in one of the file formats: TIFF, EPS or JPG; illustrations are also saved in one of these formats (See Author guidelines for details). 4. The manuscript has been examined for spelling and grammar (spell checked). 5. The title (maximum 150 characters) briefly explains the contents of the manuscript. 6. Full names (first and last) of all authors together with the affiliation address are provided. Name of author(s) denoted as the corresponding author(s), together with their e-mail address, full postal address and telephone/fax numbers are given. 7. The abstract states the objective and conclusions of the research concisely in no more than 150 words. 8. Keywords (maximum six) are provided. 9. Statement of novelty is prepared as a Word file. 10. The text adheres to the stylistic and bibliographic requirements outlined in the Author guidelines. 11. Text in normal style is set to single column, 1.5 line spacing, and 12 pt. Times New Roman font is recommended. All tables, figures and illustrations have appropriate captions and are placed within the text at the appropriate points. 12. Mathematical and chemical equations are provided in separate lines and numbered (Arabic numbers) consecutively in parenthesis at the end of the line. All equation numbers are (if necessary) appropriately included in the text. Corresponding numbers are checked. 13. Tables, Figures, illustrations, are prepared in correct format and resolution (see Author guidelines). 14. The lettering used in the figures and graphs do not vary greatly in size. The recommended lettering size is 8 point Arial. 15. Separate files for each figure and illistration are prepared. The names (numbers) of the separate files are the same as they appear in the text. All the figure files are packed for uploading in a single ZIP file. 16. Authors have read special notes and have accordingly prepared their manuscript (if necessary). 17. References in the text and in the References are correctly cited. (see Author guidelines). All references mentioned in the Reference list are cited in the text, and vice versa. 18. Permission has been obtained for use of copyrighted material from other sources (including the Web). 19. The names, full affiliation (department, institution, city and country), e-mail addresses and references of three potential referees from institutions other than (and preferably countries other than) those of any of the authors are prepared in the word file. 20. Full-colour illustration or graph from the manuscript is proposed for graphical abstract. 21. Appendices (if appropriate) as supplementary material are prepared and will be submitted at the same time as the manuscript. Privacy Statement The names and email addresses entered in this journal site will be used exclusively for the stated purposes of this journal and will not be made available for any other purpose or to any other party. ISSN: 1580-3155 Dru{tvene vesti in druge aktualnosti S92 _Acta Chim. Slov. 2016, 63, (2), Supplement Dru{tvene vesti in druge aktivnosti Slovensko kemijsko društvo Slovenian Chemical Society SKD 2016 22. Slovenski kemijski dnevi Portorož, Hotel Metropol, 28. - 30. september 2016 2. OBVESTILO Konferenca je priložnost tako za uveljavljene in izkušene raziskovalce, kot tudi za mlade, da javno pokažete svoje znanje in dosežke v obliki predavanj ali posterjev. Dobrodošli so prispevki z vseh področij kemijskih znanosti Rok za prijavo in oddajo povzetkov je 30. junij 2016 Plenarni predavatelji: Prof. dr. Vojko Vlachy {Fakulteta za kemijo in kemijsko tehnologijo, Univerza v Ljubljani, Slovenija) Prof dr. Anton Meden (Fakulteta za kemijo in kemijsko tehnologijo, Univerza v Ljubljani, Slovenija) Prof. dr. Thomas Carell (Ludwig Maximilians Universität München, Nemčija) Prof. dr. Claus Helix-Nielsen (Technical University of Denmark, Danska in Fakulteta za kemijo in kemijsko tehnologijo. Univerza v Mariboru, Slovenija) Prof. dr. h.c. Karger-Kocsis Jozsef (Polimertechnika Tanszek, Madžarska) KOTIZACIJA POMEMBNEJŠI DATUMI Pred 5. 9. Po 5. 9. Člani društva (zaposleni in zaposleni študenti 3. stopnje) 180 eur 200 eur Nečlani 210 eur 230 eur Študenti (1. in 2. stopnja in nezaposleni študenti 3. stopnje) ter upokojenci - člani društva 30 eur 45 eur študenti (1. in 2. stopnja in nezaposleni študenti 3. stopnje) - nečlani 45 eur 60 eur Spletna prijava in oddaja povzetkov 30. junij 2016 Obvestilo o sprejetju prispevkov 22. julij 2016 Program konference 5. september 2016 Zadnji rok za plačilo kotizacije po redni ceni 5. september 2016 Programski in organizacijski odbor Marija Bešter Rogač (FKKT UL), Zorka Novak Pintarič {FKKT UM), Venceslav Kaučič, predsednik (SKD), Janez Plaveč (KI) in Marjan Veber (FKKT UL). http://chem-soc.si/slovenski-kemijski-dnevi S78 Acta Chim. Slov. 2016, 63, (2), Supplement KEMIJSKI PRIROČNIK Priročnik predstavlja monografije nevarnih kemikalij, opisuje njihove kemijske in fizikalne lastnostih, praktično uporabo ter njihov vpliv na žive organizme in okolje. Namenjena je strokovnjakom, ki delujejo na področju kemije, farmacije, veterine, agronomije pa tudi poslovnim osebam, ki se ukvarjajo s proizvodnjo in prometom z nevarnimi kemikalijami ter nadzirajo njihov promet. Priročnik nudi veliko koristih podatkov osebam, ki so pogosto v stiku z naravnim okoljem (lovci, čebelarji, ribiči, ekologi), ki skrbijo za zaščito rastlin (gozdarstvo, poljedelstvo, sadjarstvo) in živali (veterina). V tem pogledu so posebno predstavljene kemikalije, katerih uporaba je dovoljena v Sloveniji na področju kmetijstva, sadjarstva in gozdarstva. Publikacija je izredno primerna kot učbenik za študente ke mije, kemijske tehnologije, farmacije in drugih sorodnih znanosti. V publikaciji so zajete zakonske določbe glede razvrščanja in označevanja kemikalij v prometu, obenem z uredbo Evropskega parlamenta in Sveta o razvrščanju, označevanju in pakiranju snovi ter zmesi, ki se začne izvajati za snovi s 1. decembrom 2010, za zmesi pa s 1. junijem 2015. obnkj (CD-ROM) znaša 15 EUR Opisi posameznih kemikalij so opremljeni tudi s CAS in s številkami carinske tarife, ki je usklajena s kombinirano nomenklaturo EU. Vsebina knjige je prilagojena dosežkom mednarodnih organizacij (Organizacija za hrano in kmetijstvo - FAO, Organizacija za ekonomsko sodelovanje in razvoj OECD, Svetovna zdravstvena organizacija WHO...), ki so v osemdesetih letih prejšnjega stoletja postavljale temelje nove svetovne politike pri obravnavi kemijskih snovi in njihovega vpliva na človekovo okolje. Priročnik je rezultat dela strokovnjakov Fakultete za farmacijo in Fakultete za kemijo in kemijsko tehnologijo. Podatki so zbrani iz različnih virov, ki so bili dosegljivi v strokovni literaturi, na spletnih straneh, v uradnih listih in drugih sprejemljivih publikacijah. Ker je takšen način obravnave nevarnih kemikalij pripravljen v slovenščini, je knjiga pomemben prispevek uresničevanju nacionalnega programa o kemijski varnosti. Avtorji knjige so Prof. Dr. Aleš Krbavčič, Prof. Dr. Aleš Obreza, Prof. Dr. Marija Soll-ner-Dolenc, Prof. Dr. Branko Stanov-nik in Mag. Milan Škrlj. Vsebinsko priročnik zajema opise blizu 800 kemikalij, IUPAC kemijski nomenkla-turni sistem za organske in neorganske spojine, opis svetovnega usklajenega sistema za razvrščanje in označevanje kemikalij (GHS), mednarodni sistem merskih enot, pregled aktivnih snovi in preparatov za zaščito rastlin registriranih v RS in osnovne farmakološko toksikološke last-Cena knjige v elektronski nosti nekaterih kemijskih funkcionalnih skupin. kemijski priročnik Dru{tvene vesti in druge aktualnosti Acta Chim. Slov. 2016, 63, (2), Supplement 95 Nomenklatura anorganske kemije Izdajo pripravili Neil G. Connellz, Ture Dambus Richard M. Hartshorn, Alan T. Hutton PRIPOROČILA IUPAC 2005 NOMENKLATURA ANORGANSKE KEMIJE ISBN 978-961-90731-8-6 Obseg: 367 str. Kemijska nomenklatura oz. poimenovanje kemijskih elementov in spojin je potrebno zato, da se vsi, ki jih uporabljajo, med seboj lahko sporazumevajo. Najpomembnejše pri tem je, da je poimenovanje spojin enotno in enoznačno, saj mora biti zagotovljeno, da si pod določenim imenom vsi predstavljajo isto kemijsko spojino. Z razvojem kemije in celotne splošne znanosti je bilo v preteklosti odkritih ali sintetiziranih ogromno število kemijskih spojin, kar se bo v prihodnosti brez dvoma nadaljevalo s še večjo intenziteto. Vzporedno z odkritji in raziskavami pa se je razvijalo in prilagajalo tudi poimenovanje kemijskih spojin. IUPAC (Mednarodna unija za čisto in uporabno kemijo) skrbi za vsklajeno delovanje na tem področju. V predgovoru k originalu knjige, ki sledi le-temu, je zato natančno opisano, kako je Mednarodna unija poimenovanje kemijskih spojin spremljala, zasledovala in spreminjala, kadar je bilo to potrebno zaradi jasnosti ali možnosti različnih razumevanj. Pred nami je tako v letu 2008 prevod »Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005« v slovenskem jeziku, le tri leta po izidu izvirnika. Zadnja slovenska nomenklatura anorganske kemije je bila izdana leta 1986, njen obseg pa je bil 86 strani (brez preglednic). Nova izdaja prevoda obsega skoraj 400 strani strokovno izjemno zahtevnega teksta. Slovenski prevod je pripravil Andrej Smalc, z recenzijo in z nekaterimi dodatnimi dejavnostmi v zvezi s pripravo za tisk pa mu je pomagal Primož Segedin. Za obsežno in strokovno korektno opravljeno delo se obema iskreno zahvaljujem. Ven~eslav Kau~i~ Predsednik Slovensko kemijsko dru{tvo Slovensko kemijsko druStvo Slovenian Chemical Society Publikacijo lahko kupite v Slovenskem kemijskem dru{tvu, Hajdrihova 19, 1000 Ljubljana Naro~ilo oddate preko dru{tvene spletne strani: http://www.chem-soc.si/publikacije/nomenklatura-anorganske-kemije Cena: 17,50 EUR Dru{tvene vesti in druge aktualnosti S96 Acta Chim. Slov. 2016, öS, (2), Supplement Koristni naslovi Slovensko kemijsko društvo www.chem-soc.si e-mail: chem.soc@ki.si Wessex Institute of Technology www.wessex.ac.uk SETAC www.setac.org European Water Association http://www.ewa-online.eu/ :URDPËRM )CIEÍ\JCE European Science Foundation "OUWDRTION www.esf.org Zing conferences www.zingconferences.com Novice europske zveze kemijskih društev (EuCheMS) najdete na: EuCheMS: Brussels News Updates http://www.euchems.eu/ Muelheim Water Award MLieiheirn Water Award www.muelheim-water-award.com Društvene vesti in druge aktualnosti e^entica Ethanol and beyond. Your reliable ethanol partner Spirit expertise Cutting-edge technology Flexibility driven business Out-of-the box thinking Invest in the future of your business. As experts in ethanol production, the quality of our products meets the highest European standards. It is not by chance, that we are one of the biggest Balkan's ethanol producer. W: WWW.ESSENTICA.EU A: 5 DUNAV BLVD. 4003 PLOVDIV. BULGARIA T: +359 32 306 783 e: SALESDESSENTICA.EU 1 0 F F I C E a) E S S E N T1 C A . E U NOVO NA SLOVENSKEM TRŽIŠČU TITRATORJI japonskega proizvajalca KEM - kontrola do 4 enot z enim brezžičnim kontrolerjem - revolucionaren hibridni (kulometričen+volumetričen KF titrator) - japonska kvaliteta za konkurenčno ceno , DONAU LAB Ljubljana Member of LPPgroup Donau Lab d.o.o., Ljubljana Tbilisijska 85 SI-1000 Ljubljana www.donaulab.si office-si@donau!ab,com / Laboratorijska oprema VVALDNER / Pohištveni sistemi, servisni moduli / Dtgestoriji, Jpfe?fHo"odsesovanie HIUMlklnu kumur^ za prašnate snovi — i Stol, varnostne" omare / Projektiranje, izvedba, servis W ji li hitro adprcim i Nal _ _ ■ ® 15 gesin s | 275 mg filmsko ni obložene 1 __ 3» '«protatno ■frffifBjj £1 "porabo ^30 ^^^ r*mslm O&lofeAift ^ tablete *« te«- Naša inovativnost in znanje za učinkovite in varne izdelke vrhunske kakovosti. Hitra Pri glavobolu, zobobolu, menslrualnih bolečinah, bolečinah v mišicah in sklepih. rešitev NalgesirfS Poletje brez bolečin. Pred uporabo natančno preberite navodilo! O tveganju in neželenih učinkih se posvetujte z zdravnikom ali s farmacevtom. k_ A Nalgesin®S — ustavi bolečino, preden bolečina ustavi vas. www.nalgesin.si www.krka.si ActaChimica Slovenica Acta ChimicaSlovenica Image represents a section of size-resolved nanoparticle number concentration time series measured in the room with laser printers in the company of spatial informatics and graphic design in Ljubljana, Slovenia during March 2014. White color represents the concentrations above 10 x 103 particle cm-3. See p. 327 Acta Chimica Slovenica Year 2016, Vol. 63, No. 2 ActaChimicaSh. Chi mica Slovenica PvémhMMHMÍB MUpJikmMi iln m I 'mm 1wIwimJw Acta* lana Chi mica Slovenica Acta< 'himica Chi mica Slovenica 4 Acta i hitan Chi mica Slovenica Acta( 1 tin lieu .Chi mica Slovenica ........... agi r^ Ac t a( hi mien ■ . Chi mica Slovenica ActaChimica^ ■ Chi mica Slovenica Actai himica Chi mica Slovenica Actac himica it Chimica Slovenica ___ 2 ÎÎjisS • « • ■ AíMChimieaSU .'tf/iiChimica.V/r Slovenica Actaí himicaSh Chimica Slovenica