pH-Potentiometric Investigation towards Chelating Tendencies of p-Hydroquinone and Phenol Iminodiacetate Copper(II)‎ Complexes

Abstract EN

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 Cu2+ with iminodiacetic phenolate/hydroquinonate ligands has been examined by pH-potentiometry.

The results reveal that the iminodiacetic phenol ligand forms mononuclear complexes with Cu2+ at acidic and alkaline pHs, and a binuclear Ophenolate-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.