Binary and ternary complexes of copper(II) involving imidazole, histamine, and L-histidine as ligands

Abstract

The complete species distribution and stability constants of the binary and ternary complexes of Cu^II with imidazole, histamine, and L-histidine as ligands were determined from pH titration data in aqueous perchlorate medium at I= 0.15 mol dm^–3(Na[ClO₄]) and 37 °C. The results show that imidazole, though a unidentate ligand, forms very stable binary and ternary complexes with Cu^II. The stability-constant data for the CuAH and CuA₂H complexes (A = histamine or histidine) suggest that their structures are similar. The ambidentate nature of the histidine ligand i.e. the ability to co-ordinate both in histamine-like and glycine-like modes is indicated from the results obtained.