pH-metric and electronic spectral measurements on the mixed ligand complexes of copper(II) containing unsubstituted imidazole and some dipeptides

Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627 012, India Manuscript received 2 May 2000, accepted 10 June 2000 CuAB, CuABH-1, CuA2B or CuA2BH-1 mixed ligand complexes have been identified in the Cull-imidazole (A)-glycyl-L-phenylalanine, L-phenyialanylglycine, glycyl-L-tyrosine, L-tyrosylglycine, L-phenylalanyl-L-tyrosine and L-tyrosyl-L-phenylalanine (B) systems. The stability constant values indicate the monodentate binding of imidazole (A) and bidentate binding of the dipeptide (B) ligands in the CuAB and CuA2B complexes. Both the pH-metric and electronic spectral results demonstrate the tridentate mode of binding of (BH-1) in CuABH-1. However, in the CuA2BH-1 species tridentate mode of binding of (BH-1) exists only to an appreciable extent