Solvatochromic absorbance probe behavior and preferential solvation in aqueous 1-butyl-3-methylimidazolium tetrafluoroborate

The hypothesis that aqueous, rather than pure, ionic liquids provide substantially altered physicochemical properties and versatile/increased solute solvation is addressed. Solvatochromic absorbance probes are utilized to gather information on aqueous solutions of a completely water-miscible ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)). A simplistic solvation model suggests possible preferential solvation of a water-soluble betaine dye by bmimBF4. The lowest-energy electronic absorption band of this dye is further used to interpret dipolarity/polarizability and hydrogen-bond donating (HBD) acidity of aqueous bmimBF4. On the basis of the responses of two other probes, N, N-diethyl-4-nitroaniline and 4-nitroaniline, dipolarity/polarizability, HBD acidity, and hydrogen-bond accepting basicity are separately assessed.