Characterization of lactam-containing binary solvents by solvatochromic indicators

Preferential solvation and intermolecular interactions of the solvatochromic indicators 4-nitroanisole, 4-nitroaniline, 4-nitrophenol, and Reichardt's dye is studied at 298.15 K in the binary solvents 2-pyrrolidinone/water, N-methylpyrrolidinone/water, and 2-pyrrolidinone/N-methylpyrrolidinone. From the experimental data the Reichardt's and Kamlet-Taft parameters were evaluated for the mixed solvents. A preferential solvation model was applied to analyze the solvation effect of the indicator by the different solvents used, and from these data useful information about solute-solvent and solvent-solvent interactions was deduced. Comparison with other thermophysical data reveals a relationship between the solvatochromic parameters and the partial molar volumes, mainly in water-containing solvents.