Proton nuclear magnetic resonance and potentiometric studies on the palladium(II)–prolylglycylalanylhistidine binary system†

Abstract

Potentiometry measurements were used to investigate equilibria of the palladium(II)–prolylglycylalanylhistidine binary system. The results obtained by this method were confirmed by ¹H NMR techniques in one and two dimensions. In strongly acidic solutions, pH < 1.0, Pd^II most probably reacts simultaneously with both proline amine and one of the imidazole nitrogens (N¹ and N³) to form a macrochelate structure. At higher pH deprotonated histidine amide nitrogen is co-ordinated, while further increase of the pH results in terminal carboxylate deprotonation.