Mixed aminocarboxylic ligand complexes

Abstract

The stabilities of some mixed proton complexes AA′H_j(A = histidine (His), lysine (Lys), histamine (Hist); A′= bi-, tri- and tetra-carboxylic acids, aspartic acid and glutamic acid) have been determined by potentiometry. Different species in each system have been found with j= 1, …, (n+m)– 1 (n and m are the maximum degrees of protonation for the two ligands). The stability of a mixed species is strictly dependent on the charges involved in the formation reactions, and a simple relationship log K=f(z_T)(where z_T is the sum of charges in the two ligands) is reported.