Effect of physicochemical properties of water-propane-2-ol mixture and temperature on thermodynamics of Cu complexation with glycine

The stability constants of Cu²⁺ complexes with glycine are determined by potentiometric method in water-propane-2-ol mixture, i.e., CuL]⁺, CuL₂ (L = Gly^–) (0.070, 0.167, 0.310 mole fraction of alcohol), and CuHL]²⁺ (0.070 mole fraction of alcohol) at 298.15, 308.15, and 318.15 K. Thermodynamic characteristics of Cu²⁺ complexation with glycine and the Gibbs energy of transfer of complex species CuL]⁺ and CuL₂ from water to a mixed solvent are calculated. The solvation-thermodynamic analysis of effects of water-propane-2-ol solvents and of separate solvation contributions of reagents to Cu²⁺ coordination with glycine is performed. The increasing stability of the CuL]⁺ and CuL₂ complexes in water-propane-2-ol as compared to that in pure water is explained by the increasing energy of solvation of complex species CuL]⁺ and CuL₂ and by the decreasing energy of solvation of Cu²⁺ and Gly^– ions.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 311–318.Original Russian Text Copyright © 2005 by Tsurko, Bondarev, Shikhova, Khrebto.