MIXED AMINOCARBOXYLIC LIGAND COMPLEXES

The stabilities of some mixed proton complexes AA'H-j (A = histidine ( His), lysine (Lys), histamine (Hist); A' = bi-, tri- and tetra-carboxy lic acids, aspartic acid and glutamic acid) have been determined by po tentiometry. Different species in each system have been found with j = 1,..., (n + m) - 1 (n and m are the maximum degrees of protonation fo r the two ligands). The stability of a mixed species is strictly depen dent 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.