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

•Stable mixed ligand complexes of MNta with dipeptides at physiological pH value.•The thermodynamic and spectrophotometric data evident the various coordination mode of dipeptides.•NH2, CO-coordination mode of dipeptides in complexes MNtaL.•NH2, N−- or NH2, N−, COO-coordination modes of dipeptides in complexes MNtaLH−1.

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-13- complexes have been determined. The probable coordination mode of the complexone and dipeptide molecules in the mixed-ligand complexes was discussed.

Graphical abstractThe mixed ligand complex formation of copper(II) and nickel nitrilotriacetates with dipeptides containing the glycine and alanine residues has been investigated by means of calorimetry, pH-potentiometry and Vis spectroscopy. The received data evident various coordination modes of dipeptides in complexes MNtaL (NH2, CO-coordination) and MNtaLH−1 (NH2, N−- or NH2, N−, COO-coordination). The formation of stable mixed complexes of MNta with dipeptides at physiological pH value should be accounted during chelation therapy.Figure optionsDownload full-size imageDownload as PowerPoint slide