The comparison of structural and magnetic properties of cobalt(II) and nickel(II) acetates with N-donor ligands

V pričujočem delu sem se ukvarjala s sintezo in karakterizacijo novih koordinacijskih spojin kobaltovega(II) in nikljevega(II) acetata z N-donorskimi ligandi. Med slednjimi sem uporabljala komercialne 2-, 3- in 4-aminopiridin (apy), piridin-2-karboksamid (pikolinamid) (pia), piridin-3-karboksamid (nikotinamid) (nia) in piridin-4-karboksamid (izonikotinamid) (isn). Za centralne ione sem izbrala kobaltove in nikljeve ione, saj je bila večina sintez že opravljena na podobnih sistemih z bakrovimi ioni. Sintez sem se lotila predvsem zaradi zanimanja, kako se spreminjajo strukturne, spektroskopske in magnetne lastnosti spojin, ki nastanejo, če centralnim ionom dodajamo ligande z enakimi substituentami in z različnim mestom vezave na aromatski obroč. Nove spojine sem sintetizirala s kobaltovim(II) acetatom di- in tetrahidratom ter nikljevim(II) acetatom tetrahidratom ter zgoraj naštetimi ligandi v različnih topilih (največkrat so bili uporabljeni metanol, voda, dimetilformamid in diklorometan). Slednja sem izbirala glede na topnost kemikalj v njih oziroma hitrost raztapljanja, želeno temperaturo reakcije, predhodnih poročil in topnosti produkta v samih topilih. Reakcije sem izvajala pri sobni temperaturi na mešalu, pod refluksom ali solvotermalno pri povišani temperaturi in tlaku. Sintetizirane spojine smo karakterizirali z rentgensko analizo na monokristalu ter infrardečo spektroskopijo, poleg tega pa smo določali njihove magnetne lastnosti. Kot pomožno metodo smo uporabljali rentgensko praškovno difrakcijo. Nove spojine, ki sem jih uspela sintetizirati, so enojedrne: [Co(O2CCH3)2(2–apy)2], [Co(O2CCH3)2(4–apy)2(H2O)2], [Ni(O2CCH3)2(4–apy)2(H2O)2], [Co(nia)2(H2O)4](CH3COO)2• 2H2O, [Ni(O2CCH3)(pia)2•H2O](CH3COO)•2H2O, [Ni(O2CCH3)2(isn)2(H2O)]•C3H7NO, večjedrne: {[Co(O2CCH3)2(3–apy)2]•H2O}n in {[Ni(O2CCH3)2(3–apy)2]•H2O}n, uspela pa sem sintetizirati tudi dvojedrno spojino: [Co2(O2CCH3)4(isn)4]•2C3H7NO. Zelo zanimiva je spojina [Co(O2CCH3)2(2–apy)2]. Uspela sem namreč sintetizirat tri polimorfne modifikacije te spojine, monoklinsko, triklinsko in ortorombsko. Poleg tega sta zanimivi strukturi spojin kobaltovega(II) oziroma nikljevega(II) acetata s 3-aminopiridinom, saj tvorita enote [M(O2CCH3)2(3–apy)2] (M = Co ali Ni), ki so preko mostovnih 3-apy ligandov povezane v polimerne verige. Vsi kompleksi se v magnetnem polju obnašajo paramagnetno. Centralni ioni so dovolj narazen, da med njimi ne prihaja do interakcij. Rezultati meritev so pokazali tudi, da so izmerjeni magnetni momenti v skladu s teoretičnimi podatki za Co2+ in Ni2+. IR spektri kažejo razlike v –NH2 valenčnih nihanjih, nihanjih obročev in −COO− skupine.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