PROTON NUCLEAR-MAGNETIC-RESONANCE AND POTENTIOMETRIC STUDIES ON THE PALLADIUM(II)-PROLYLGLYCYLALANYLHISTIDINE BINARY-SYSTEM

Potentiometry measurements were used to investigate equilibria of the palladium(II)-prolylglycylalanylhistidine binary system. The results o btained by this method were confirmed by H-1 NMR techniques in one and two dimensions. In strongly acidic solutions, pH < 1.0, Pd-II most pr obably reacts simultaneously with both proline amine and one of the im idazole nitrogens (N-1 and N-3) to form a macrochelate structure. At h igher pH deprotonated histidine amide nitrogen is co-ordinated, while further increase of the pH results in terminal carboxylate deprotonati on.