Thermodynamic characteristics of the formation reactions of nickel(II) glycinates and the solvation of reagents in aqueous ethanol solutions

Enthalpies of complexation reactions between nickel(II) and the glycinate ion in mixtures of water with ethanol containing up to 0.5 mole fraction ethanol were obtained by the calorimetric titration method at 298 K. With increasing ethanol concentration exothermicity of complexation was found to increase slightly for the first coordination step. The results obtained were analyzed from the standpoint of solvation approach based on thermodynamic characteristics of all reagents. It was shown that the main cause of the increase in the exothermicity of complexation reactions is the weakening of ligand solvation with increasing ethanol concentration.