Potentiome Tr1C Studies, Synthesis and Characterization of Mixed-Ligand Complexes of Copper(II), Nickel(II), Cobalt(II) and Manganese(II) with N-(2ACETAM1D01M1N0D1ACETIC) Acid as the Primary Ligand and Histidine as the Secondary One

Abstract The formation equilibria of new ternary mixed-ligand complexes of copper(II), nickel(II), cobalt(Il), and manganese(II) with N-(2-acetamidoiminodiacetic) acid (H2ADA) as the primary ligand and histidine (His) as the secondary one were investigated. The formation constants of these complexes have been determined at 25.0 °C in 0.3 M aqueous Na2SO4 solution. They show that the ternary complexes are more stable than the corresponding binary ones. The ternary complexes have been synthesized and were characterized using elemental analyses, molar conductance, 1R spectra, magnetic measurements as well as electronic and ESR spectra. The spectral results support the binding of H2ADA and histidine with, respectively, the NOO and NO sites, to copper(II), cobalt(II), and manganese(II) providing an octahedral geometry, while nickel(II) is bonded to the same ligands in a bidentate manner by the OO and NO donor groups giving a square-pyramidal complex. The other axial sites are occupied by OH− or H2O groups. Mag...