Water-DMSO mixtures preferential solvation

Eu(III) is preferentially solvated by DMSO in water-DMSO mixtures over the whole range of solvent composition, as demonstrated by luminescence lifetime measurements (Tanaka et al. 1988). Similarly, solutions of europium chloride, nitrate and acetate in DMSO exhibit a considerable luminescence enhancement (Chrysochoos and Evers 1973a). Addition of large amounts of water has no effect at all, while adding very small quantities of DMSO to aqueous solutions of Eu(III) induces drastic changes in the transition probabilities. This clearly demonstrates the stronger coordination properties of DMSO as compared to water. 

Local concentration of solvent molecules changes substantially. This can occur in hquid mixtures when the solute groimd and excited states are preferentially solvated by different solvent components. It has been observed in simulations of SD in water-dimethyl sulfoxide (DMSO) -, water-methanoF and n-hexane-methanol mixtures," as well as in om work in progress on SD in benzene-acetonitrile mixtures. ... 

An outstanding exception is the solvation of ions in dimethylsulphoxide (DMSO)-water mixtures. While in dimethylsulphoxide AG (Ag ) related to water is negative, in highly aqueous DMSO mixtures Ag is preferentially hydrated The change of preferential solvation of an ion with solvent composition has also been noticed for other ions This behavior can be attributed to the stabilization ... 

HP he study of the behavior of electrolytes in mixed solvents is currently arousing considerable interest because of its practical and fundamental implications (1). Among the simpler binary solvent mixtures, those where water is one component are obviously of primary importance. We have recently compared the effects of small quantities of water on the thermodynamic properties of selected 1 1 electrolytes in sulfolane, acetonitrile, propylene carbonate, and dimethylsulfoxide (DMSO). These four compounds belong to the dipolar aprotic (DPA) class of solvents that has received a great deal of attention (2) because of their wide use as media for physical separations and chemical and electrochemical reactions. We interpreted our vapor pressure, calorimetry, and NMR results in terms of preferential solvation of small cations and anions by water and obtained... 

Solvation of f-element cations in mixed aqueous solvents has been studied using the fluorescence technique. With Eu(III) ion as a probe (Tanaka et al. 1988, Lis and Choppin 1991), in water-acetone, water-acetonitrile and water-1,4-dioxane, the first solvation sphere is occupied exclusively by water molecules even at bulk-phase mole fractions of water as low as 0.1 (fig. 6, curve I). However, in solvents with more basic donors such as DMSO (DMSO is dimethylsulphoxideX the metal ion is preferentially solvated by DMSO even for very low mole fractions of DMSO in the solvent (curve II, fig. 6). Less regular behavior can be expected for systems in which (a) strong interactions exist between the components of the solvent mixture or between the coordinated... 

The preferential solvation of D-glucans, including amylose, in dimethyl-sulphoxide (DMSO)-water mixtures has been studied by gel permeation chromatography. In solvent mixtures containing less than 33% DMSO, each D-glucan was... 

---