Irving-williams order in the framework of connectivity index 3xv enables simultaneous prediction of stability constants of bivalent transition metal complexes

Abstract

Logarithms of stability constants, log K1 and log β2, of the first transition seriesmetal mono- and bis-complexes with any of four aliphatic amino acids (glycine, alanine, valine and leucine) decrease monotonously with third order valence connectivity index, 3x v, from Cu2+ to Mn2+. While stability of the complexes with the same metal is linearly dependent on 3x v, stability constants of Mn2+, Fe2+, Co 2+, and Ni2+complexes with the same ligand show a quadratic dependence on 3xv. As Cu2+ complexes deviate significantly from quadratic functions, models for the simultaneous estimation of the stability constants, yielding r = 0.999 (S.E. = 0.05) and r = 0.998 (S.E. = 0.11), for log K1 and log β2, respectively, were developed only for Mn2+, Fe2+, Co2+, and Ni2+ complexes with amino acids. © 2011.