Thermodynamic study of mixed-ligand complex formation of copper(II) and nickel(II) nitrilotriacetates with dipeptides in solution

The mixed-ligand complex formation in the systems M2+–Nta3−–L− (M = Cu, Ni; L = GlyGly, AlaAla) has been calorimetrically, pH-potentiometrically and spectrophotometrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the MNtaL2− and MNtaLH - 1 3 - complexes have been determined. The probable coordination mode of the complexone and dipeptide molecules in the mixed-ligand complexes was discussed.