Structural, spectral and magnetic properties of carboxylato cobalt(II) complexes with heterocyclic N-donor ligands: Reconstruction of magnetic parameters from electronic spectra

Heteroleptic cobalt(II) complexes with general formula of [Co(N-base)2(car)2(H2O)2], have been synthesized and structurally characterized; the N-base stands for neutral N-donor ligands: iso-quinoline (iqu), [1]benzofuro[3,2-c]pyridine (bzfupy), 1-(pyridin-3-yl)[1]benzofuro[3,2-c]pyridine (1-py-bzfupy) and 1-phenyl-1H-imidazole (bylim); car = acetato (ac) or benzoato (bz) ligands. The structure of [Co(iqu)2(ac)2(H2O)2] 1, [Co(bzfupy)2(ac)2·(H2O)2] 2, [Co(1-py-bzfupy)2(ac)2(H2O)2]·H2O 3 and [Co(bylim)2(bz)2(H2O)2] 4 complexes is formed of the {CoN2O2O2′} chromophore. These complexes were subjected to magnetochemical investigation down to 2 K (susceptibility and magnetization measurements). They show magnetic behavior typical for the zero-field splitting systems. The axial parameter of the zero-field splitting adopts large values, D = 80–103 cm−1. We have analyzed electronic spectra of the complexes in detail with aim to extract the crystal-field parameters. These have been used for reconstruction of the magnetic parameters. The calculated axial ZFS parameters are in good agreement with the experimental values.