Heteroligand Copper(II), Nickel(II), and Cobalt(II) complexes with isonicotinic acid hydrazide and L-histidine

Abstract

Complex formation in the ternary systems copper(II)/nickel(II)/cobalt(II) – isonicotinic acid hydrazide – L-histidine was studied by the methods of spectrophotometry and mathematical modeling in an aqueous solution with 0.1 mol dm–3 KNO3 as a background electrolyte. The compositions, formation constants, and spectral parameters of the heteroligand complexes with a metal/hydrazide/amino acid ratio of 1:1:1 were determined. It was found that the heteroligand complexes with the neutral form of isonicotinic acid hydrazide have higher stability values than those with the protonated form. The stability of bis- and tris-complexes of the same composition in the series copper(II) – nickel(II) – cobalt(II) is in agreement with the Irving–Williams order. Three isomers of the heteroligand complex of nickel(II) with the protonated form of isonicotinic acid hydrazide and histidine zwitterion were optimized by the method of molecular mechanics. In the system with cobalt(II), a reversible interaction with atmospheric oxygen was revealed.