Thermodynamic and NMR studies of mixed-ligand complex formation of mercury (II) ethylenediaminetetraacetate with dipeptides in solution

pH-potentiometry, calorimetry and 1Н and 13С NMR spectroscopy have been used to study the mixed-ligand complex formation in the systems Hg2+–Edta4−–L− (L = GlyGly, AlaAla) in aqueous solution at 298.15 K and ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the HgEdtaL3−, and HgEdtaLH-14- complexes have been determined. The most probable coordination mode for the complexone and the dipeptide in the mixed-ligand complexes was discussed.

The mixed ligand complex formation of mercury (II) ethylenediaminetetraacetate with dipeptides (L = GlyGly, AlaAla) has been investigated by means of calorimetry, pH-potentiometry and NMR spectroscopy. The received data evident various coordination modes of dipeptides in complexes HgEdtaL (NH2, CO-coordination) and HgEdtaLH−1 (NH2, N−- or NH2, N-, COO-coordination). The formation of stable mixed complexes of HgEdta with dipeptides at physiological pH value should be accounted during chelation therapy.Figure optionsDownload as PowerPoint slideHighlights
► Stable mixed ligand complexes of HgEdta with dipeptides at physiological pH value.
► The thermodynamic and NMR data evident the various coordination mode of dipeptides.
► NH2, CO-coordination mode of dipeptides in complexes HgEdtaL.
► NH2, N−- or NH2, N−, COO-coordination modes of dipeptides in complexes HgEdtaLH−1.