PREFERENTIAL SOLVATION OF SILVER(I)-CRYPTAND-2,2,2 PERCHLORATE COMPLEX IN WATER PLUS ACETONITRILE AND METHANOL PLUS ACETONITRILE MIXTURES

The preferential solvation of silver(I)-cryptand-2,2,2 perchlorate complex in methanol (MeOH) + acetonitrile (AN) and water + AN mixtures (25 degrees C) was studied by determination of Gibbs transfer energies and solvent transport numbers over the complete range of solvent compositions. The Gibbs transfer energies of the complex salt were split into ionic components by applying the negligible liquid junction potential (nLJP) assumption and reference electrolyte methods using tetraphenylarsonium tetraphenylborate (TATB) in MeOH + AN and water + AN mixtures respectively. The transfer energy of the complexed cation is negative and decreases continuously with the addition of AN (up to X(AN) = 0.9 in MeOH + AN mixtures and up to X(AN) = 0.5 in water + AN mixtures), while that of perchlorate ion increases under the same conditions in both mixed solvents. The solvent transport number Delta(AN) of AN is positive and passes through a maximum of 5.0 at X(AN) = 0.55 in MeOH + AN mixtures and 8.7 at X(AN) = 0.45 in water + AN mixtures. The results suggest a heteroselective solvation of the salt, with the complex cation being selectively solvated by AN and the perchlorate ion by MeOH or water in the two mixed solvents.