Quantum chemical simulation of trans- and cis-isomers of bis-chelate azomethine complexes of Ni(II), Pd(II), and Pt(II) with the MN2Y2 (Y = O, S, Se) coordination core

Within density functional theory the experimentally observed stereoeffects of the ligand environment in low-spin bis-chelates of Ni(II), Pd(II), and Pt(II) with aromatic azomethines is modeled. It is shown that complexes with the MN2O2 coordination core are characterized by the trans-configuration and in complexes with MN2S2 or MN2Se2 cores the stabilization of the cis-configuration occurs. The relationship is found between the composition of metal cycles and their conformation (an inflection along the donor atom line), the degree of steric hindrances in the cis-configuration due to the interligand interaction of R substituents at azomethine nitrogen atoms and the relative stability of cis- and trans-isomers of the complex.