Solvatochromism in some cosolvent mixtures of sulfolane and aliphatic alcohols: a tool to predict preferential solvation

The phenomenon of solvatochromism for three indicator solutes, namely para-nitroaniline, N,N-dimethyl-pnitroaniline, and the betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-diphenylphenolate, was studied at 303.15 +/- 0.1 K by means of UV-vis absorption measurements. The spectral shifts of these dyes in different mole fractions (0.0-1.0) of binary mixtures of sulfolane with eight alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol) were analyzed to investigate preferential solvation of them in terms of both the solute-solvent and the solvent-solvent interactions. A modified theoretical model (solvent exchange model) was successfully employed to calculate preferential solvation parameters and to obtain information into the contribution of intermolecular interactions to the local and bulk mole fraction distribution of solvation species. It was found that the solvation shell of the dyes is mainly affected by the solvent-solvent interactions, and in all binary mixtures, the studied solvation behavior was non-ideal.