The solvatochromic parameters (ET(N), normalized polarity parameter; pi*, dipolarity/polarizability; beta, hydrogen-bond acceptor basicity; alpha, hydrogen-bond donor acidity) were determined for binary solvent mixtures of 1-(1-butyl)-3-methylimidazolium tetrafluoroborate ([bmim]BF4) with water, methanol, and ethanol at 25 degrees C over the whole range of mole fractions. In nonaqueous solutions, the value of the mixture increases with mole the fraction of [bmim]BF4 and then decreases gradually to the value of pure [bmim]BF4. Positive deviation from ideal behavior was observed for the solvent parameters ET(N), pi*, and alpha, whereas the deviation of the beta parameter is negative. The applicability of the combined nearly ideal binary solvent/Redlich-Kister equation for the correlation of various solvatochromic parameters with solvent composition was proved too for the first time. This equation provides a simple computational model to correlate and/or predict various solvatochromic parameters for many binary solvent systems. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute-solvent and solvent-solvent interactions have been applied for interpretation of the results.

No abstract

Structural and intermolecular interactions of solvatochromic probes 4-nitroaniline, 4-nitroanisole, and Reichardt's dye were investigated in the binary mixtures of 2-hydroxy ethylammonium formate as an ionic liquid with N,N-dimethyl formamide, dimethyl amine, and dimethyl sulfoxide. Solvatochromic parameters (ETN, normalized polarity parameter; pi*, dipolarity/polarizability; beta, hydrogen-bond acceptor basicity; alpha, hydrogen -bond donor acidity) were determined in ionic liquid mixtures at 25 degrees C using UV-vis spectroscopy. ETN parameters obtained from absorbance of Reichardt's dye within various mixtures of ionic liquid were observed to be higher than predicted values from ideal additive behavior. Synergistic solvation behavior for some mixtures was observed. The combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation was used for various parameters correlation to predict solvatochromic parameters. Preferential solvation model was applied for the first time in the ionic liquid mixtures to study solvent mixtures effects on solvation of indicators, and from these information solute-solvent and solvent-solvent interactions were interpreted. Preferential solvation (specific solute-solvent interactions) or the solvent-solvent interaction is the reason for deviation from ideal behavior of probes.