POTENTIOMETRIC AND SPECTROSCOPIC STUDIES OF THE COMPLEX-FORMATION BETWEEN VANADYL IONS AND DI-GALACTONURIC AND TRI-GALACTURONIC ACIDS

Potentiometric and spectroscopic (EPR, CD and absorption spectra) studies were performed on two systems VO(IV)-di-D-galacturonic acid and VO(IV)-tri-D-galacturonic acid. The carboxylate function was shown to act as an anchor binding site. The adjacent deprotonated hydroxyl group co-ordinates to close the chelate ring. The bulky ligands protect the formation of the bis-complexes and therefore at pH above 6 the hydroxyspecies predominate.