title: pH-Potentiometric Investigation towards Chelating Tendencies of p-Hydroquinone and Phenol Iminodiacetate Copper(II) Complexes.
abstract: Copper ions in the active sites of several proteins/enzymes interact with phenols and quinones, and this interaction is associated to the reactivity of the enzymes. In this study the speciation of the Cu(2+) with iminodiacetic phenolate/hydroquinonate ligands has been examined by pH-potentiometry. The results reveal that the iminodiacetic phenol ligand forms mononuclear complexes with Cu(2+) at acidic and alkaline pHs, and a binuclear O(phenolate)-bridged complex at pH range from 7 to 8.5. The binucleating hydroquinone ligand forms only 2 : 1 metal to ligand complexes in solution. The pK values of the protonation of the phenolate oxygen of the two ligands are reduced about 2 units after complexation with the metal ion and are close to the pK values for the copper-interacting tyrosine phenol oxygen in copper enzymes.
authors.affiliation: Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus.
authors.forename: Marios
authors.initials: M
authors.lastname: Stylianou
authors.forename: Anastasios D
authors.initials: AD
authors.lastname: Keramidas
authors.forename: Chryssoula
authors.initials: C
authors.lastname: Drouza