Ground States of the Square Planar Low-Spin Cobalt(II) Complexes

In order to investigate the ground state configuration of some square planar cobalt(II) complexes such as Schiff base complexes of the cis-[CoN2O2] type, whose ESR spectra are quite different from those of cobalt(II) phthalocyanine and porphyrins, the spin-orbit matrix based on the four zero-order wave functions, (yz)1, (xz)1,(z2)1, and (xy) were diagonalized on assuming reasonable values for necessary parameters. The result has clearly shown that an unpaired electron is localized in dyz orbital in the ground state for these complexes. ESR spectra of a series of cobalt(II) complexes with N4-macrocyclic ligands were measured and interpreted in terms of the conclusion obtained here.