Cu(ll), Co(ii), and Ni(ii)– Antioxidative Phenolate-Glycine Peptide Systems: An Insight into Its Equilibrium Solution Study

The stability of complex formation between divalent transition metal ions, phenolates and glycine peptides was studied at 298.15 K in aqueous solution with an ionic strength of 0.15 mol· dm−3 NaNO 3. HYPERQUAD 2008, a program based on nonlinear least-squares curve fitting, was used to determine the stability constants of the complexes formed from the pH-potentiometric data. The trends in stability constants of the complexes and the contribution of deprotonated or undeptotonated amide peptide in the stability constant were discussed. From the stability constants that obtained, the representative species distribution diagrams of copper complexes were provided by the HYSS 2009 program. In addition, structures of the formed complexes were predicted by using the Gaussian 09 program. The Gibbs free energies of these complexes were also evaluated in the simulation