Mixed-ligand complex formation of mercury (II) ethylenediaminetetraacetate with cysteine and methionine in aqueous solution

The mixed-ligand complex formation in the systems Hg2+–Edta4−–L (L = Cys2−, Met−) has been studied by means of calorimetry, pH-potentiometry and NMR spectroscopy in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the HgEdtaL, HgEdtaHL and (HgEdta)2L complexes have been determined. The most probable coordination mode for the complexone and the amino acid in the mixed-ligand complexes is discussed.

Graphical abstractThe bridge function of amino acids in binuclear complexes of the type (HgEdta)2L (L = Cys, Met) has been investigated by means of calorimetry, pH-potentiometry and NMR spectroscopy. The received data evident the participation of S-CH3 group of Met in coordination process and its ambidentate character in mixed complex.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The unusual bridge function of amino acids in binuclear complexes of the type (HgEdta)2L (L = Cys, Met) has been investigated. ► The thermodynamic and NMR data evident the participation of S-CH3 group of Met in coordination process. ► The amino acid can be monodentate in the mononuclear mixed complex or bidentate with the bridging function in the binuclear complex.