Solution equilibria of mixed metal mixed ligand complexes of copper(II), nickel(II) and zinc(II) with glycylalanine and imidazole

Abstract

Solution equilibria of mixed metal mixed ligand complexes of Cu^II, Ni^II and Zn^II with glycylalanine and imidazole investigated in aqueous solution by potentiometry, spectrophotometry and electron paramagnetic resonance spectroscopy. The stability

constants of the binary, ternary and quaternary complexes are determined and it is obtained for the following species (A¯ = glycylalaniate and B= imidazole) : M²⁺, AH₂⁺, AH, A¯ , BH⁺, B, M(OH)⁺, M(OH)₂, M(A)⁺, M(A)(OH), M(B)²⁺, M(B)(OH)⁺, M(A)(B)⁺, M₂(A)₂ (B)²⁺, M₂(A)₂(B-H)⁺, M¹M²(A)₂(B)²⁺ and M¹M²(A)₂(B-H)⁺.(N₁H) deprotonation of bidentate coordinated bridging imidazole ligand in the binuclear complexes at <i>p</i>H<i>></i>6.5 is evident from spectral measurements. Stability constants of binary M(A)⁺,<i> </i>M(B)²⁺ and ternary M(A)(B)⁺<i> </i>complexes follow Irving-Williams order.