Primerjava strukturnih in magnetnih lastnosti kobaltovih(II) in nikljevih(II) acetatov z izbranimi N-donorskimi ligandi : doktorska disertacija

slovenian

doktorska dela

2012

cobalt(II) acetate tetrahydrate   IR spectroscopy   magnetic measurements   nickel(II) acetate tetrahydrate

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

The presented work describes syntheses and characterization of new coordination compounds of cobalt(II) and nickel(II) acetate with N-donor ligands, such as 2-, 3- and 4-aminopyridine, picolinamide, nicotinamide and isonicotinamide. As central ions cobalt(II) and nickel(II) ions were chosen while most of similar syntheses had already been done on copper(II) ion. I was interested in similarities and differences in structural, spectroscopic and magnetic properties of the compounds which have different central ion and the same ligands or the same central ions and ligands with substituent that occupies a different position. The new compounds were synthesized by cobalt(II) acetate di- and tetrahydrate or nickel(II) acetate tetrahydrate and the above mentioned ligands in different solvents (mostly methanol, water, dimethylformamide, dichloromethane). The latter were chosen with regard to the solubility of the chemicals or the velocity of their dissolution, the temperature of the desired reaction, the literature reports and the solubility of the product. The reactions were made at room temperature on a stirrer, under reflux or solvothermal at high temperature and pressure. The compounds were characterized structuraly by single-crystal X-ray diffraction analysis, spectraly by infrared spectroscopy and magnetic measurements. As a secondary method we used X-ray powder diffraction. The new compounds I synthesized are mononuclear: Co(O2CCH3)2(2-apy)2, Co(O2CCH3)2(4-apy)2(H2O)2, Ni(O2CCH3)2(4-apy)2(H2O)2, Co(pia)2(H2O)2(CH3COO)2 4H2O, Co(nia)2(H2O)4(CH3COO)2 2H2O, Ni(O2CCH3)(pia)2(H2O)(CH3COO) 2H2O, Ni(O2CCH3)2(isn)2(H2O) C3H7NO, polynuclear: {Co(O2CCH3)2(3-apy)2 H2O}n, {Ni(O2CCH3)2(3-apy)2 H2O}n, and I also manage to synthesize a dinuclear one: Co2(O2CCH3)4(isn)4 2C3H7NO. The very interesting compound is Co(O2CCH3)2(2-apy)2, namely I manage to prepare three polymorphic modifications of it. Very interesting are also the compounds of cobalt(II) and nickel(II) acetate with 3-aminopyridine where Co(O2CCH3)2(3-apy)2 units are through 3-aminopyridine bridging ligands connected into polymeric chains. All of the compounds have paramagnetic behaviour. The distances between the central metal ions are long enough, so there are no interactions between them. The experimentally obtained values are close to theoretical values for Co2+ or Ni2+. Some differences in -NH2 streching vibrations, ring and -COO- vibrations in IR spectra were observed.

07.08.2023