Stability Constants of Copper(II) Glycylglycinate Complexes in Water–Dimethylsulfoxide Solutions

Stability constants of normal and copper(II) bis-glycylglycinate complexes in water–dimethylsulfoxide solutions of variable composition are determined via potentiometry at a temperature of 298 K and an ionic strength of the solutions of 0.1 (NaClO 4 ). The dissociation constants of the peptide group in copper(II) glycylglycinate in water–dimethylsulfoxide mixtures are calculated. It is found that the stability of copper(II) complexes with glycylglycinate ion grows along with the content of dimethylsulfoxide. Contributions from the resolvation of reagents in a water–dimethylsulfoxide solvent to the change in the Gibbs energy of copper(II) glycylglycinate formation are estimated.