Potentiometric, thermodynamics and coordination properties for binary and mixed ligand complexes of copper(II) with cephradine antibiotic and some N- and O-bound amino acids (α-alanine and β-alanine)

Abstract

As a model for forecasting the ligand properties of antibiotics in living organisms, formation equilibria of binary and ternary Cu(II) complex with Cephradine (Cep) antibiotic in presence of α-alanine (α-Ala) and β-alanine (β-Ala) amino acids have been studied using the potentiometric titrations. Many factors were investigated like the formation constant, protonation constant, composition and stabilities of the species formed with copper(II) ions in water and water-ethanol solutions of different compositions. The thermodynamics were calculated and the data clarified. The pH-titrations of the reaction mixtures have been revealed 1:1:1 (Cu:Cep:amino acid (AA)) ternary complex formation. By aid of Δ log10K, Δ log10β and log10X parameters, quantitative matching of the stability of mixed-ligand complexes and the stability of the binary complexes was done. Investigations of the stability of the ternary complexes relative to their corresponding binary complexes indicated that formation of ternary complexes is more preferable than binary metal complexes. The obtained data from protonation of the investigated cephradine antibiotic and β-Ala/α-Ala amino acids and their complex formation equilibria will be a significant contribution to workers carrying out mechanistic studies in biological media.