Mixed Ligand Complex Formation Reactions and Equilibrium Studies of Cu(II) with Bidentate Heterocyclic Alcohol (N,O) and Some Bio-Relevant Ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(HMI)L (HMI=4-Hydroxymethyl-imidazole, L=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(HMI)L and Cu(HMI,H-1)(L) complexes. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Delta log (10) K and log (10) X. The effect of the side chains of amino acid ligands (Delta(R)) on complex formation was discussed. The concentration distributions of various species formed in solution were also evaluated as a function of pH. The thermodynamic parameters Delta HA degrees and Delta SA degrees calculated from the temperature dependence of the equilibrium constants are investigated. The effects of dioxane as a solvent, on the protonation constant of HMI and the formation constants of Cu-II-HMI complexes, were discussed.