Ternary complexes of zinc(II) with nitrilotriacetic acid and some selected thiol amino-acids and related molecules

Solution equilibria of the system zinc(II)-nitrilotriacetic acid (NTA)-secondary ligand (L) have been studied. The secondary ligands investigated are thiol amino-acids and related molecules. Potentiometric titrations of reaction mixtures containing equimolar Zn(2+), NTA and secondary ligand have shown the formation of 1 : 1 : 1 ternary complexes. The formation constants of these complexes have been determined at 25 degrees (mu = 0.1M, KNO(3)). The mode of chelation is discussed.