Stability of cadmium(II) complexes with glycinate ion in dimethyl sulfoxide aqueous solutions
Resumo
The stability constants of cadmium(II) complexes with glycine anion in aqueous dimethyl sulfoxide solutions were determined by potentiometric titration at a temperature of 298 K and an ionic strength of 0.1 M solutions at sodium perchlorate background. When the concentration of dimethyl sulfoxide in the solution increases, an increase in the stability of cadmium(II) glycinates is observed. The obtained data are compared with the literature values of stability constants in aqueous solutions of dimethylsudium oxide glycinate complexes with d-metal ions, as well as cadmium(II) complexes with N,O-donor ligands. The Gibbs energies of the cadmium(II) glycinate complex transfer from water to aqueous dimethyl sulfoxide were calculated using the literature data. The contribution of the reactants' resolvation to the Gibbs energy change of the complex formation was considered. We concluded that the increased stability of cadmium(II) glycinate in aqueous solutions of dimethyl sulfoxide is mainly due to a weakening of the solvate state of the ligand.