Thermodynamics of the Mixed-Ligand Complex Formation of Mercury(II) Ethylenediaminetetraacetate with Dipyridine and Phenanthroline in Aqueous Solution

The formation of the mixed-ligand complexes HgEdtaL2−, where L = 2,2′-dipyridine (Dipy) or 1,10-phenanthroline (Phen), was studied by calorimetry and pH titration at 298.15 K and the ionic strength I = 0.5 (NaClO4, KNO3). The heats of the formation of the dipyridine and phenanthroline complexes of mercury(II) determined at 298.15 K and the ionic strength I = 0.1 (NaNO3, KNO3). A probable coordination mode of the ligands in a mixed complex was discussed.