Ligand field spectroscopy and chemical bonding in Cr3+-, Fe3+-, Co2+- and Ni2+-containing oxidic solids: Influence of the inductive effect of the competing bonds and magnetic interactions on the degree of covalency of the 3d M–O bonds

The correlations between B35 and the ionic-covalent parameter ICPnn for various 3dn electronic configurations (3d3, 3d5, 3d7, 3d8) in mixed oxides reveal the effect of the nearest cationic shell on bonding in the transition metal coordination polyhedron. The variations of B35 with the optical basicity calculated from the valence and coordination numbers of the component cations show that the physical interpretation of the Racah parameter in terms of so-called covalency effects should be viewed with some caution. A much closer correlation between the Racah parameters and the degree of covalency of M–O bonds is achieved when the inductive effect and the influence of magnetic interactions are taken into account.