Composition and Stability of Copper(II) Complexes with [2.2.2]Cryptand in Aqueous and Aqueous Ethanol Solutions

Coordination equilibria in aqueous ethanol solutions of copper(II) and [2.2.2]cryptand are studied via spectrophotometry and potentiometry. It is shown that copper(II) ions form mononuclear, dinuclear, and protonated complexes with [2.2.2]cryptand. The stability constants of the formed complexes are determined potentiometrically at T = 298 K and mu -> 0 in aqueous and aqueous ethanol solutions. It is established that an increase in ethanol concentration of the solution improves the stability of mono- and dinuclear complexes of copper(II) with [2.2.2]cryptand and reduces the stability of the protonated complex. It is demonstrated that the rise in the negative value of the Gibbs energy of formation of mononuclear copper(II) cryptate in aqueous ethanol mixtures is due to weakening the solvation of the complexing ion.