Experimental and Theoretical Studies of Preferential Solvation of 4-Nitroaniline and 4-Nitroanisole in an Amino Acid Ionic Liquid with Molecular Solvents

Abstract

Amino acid ionic liquids (AAILs) are a new green class of ILs. Maximum wave numbers of 4-nitroaniline and 4-nitroanisole based on the solvatochromic method were calculated in binary mixtures of tetra butyl ammonium glycinate ([N4444][Gly]) with both protic and aprotic molecular solvents to understand the microsphere solvations and preferred solvents. These investigations showed that the effects of glycinate in [N4444][Gly] led to high hydrogen-bond basicity (β) and polarizability (π*), and they illustrated that normalized polarity (ETN), π*, and β of [N4444][Gly] are more than those of molecular solvents. The preferential solvation model presented that the probes prefer to be solvated by either IL or mixed solvents. Molecular dynamic (MD) simulations confirmed the preferential solvation model results and were used to analyze the microsphere solvation of dyes. It has been found out that the glycinate attend the microsphere solvation of 4-nitroaniline to have hydrogen bond interactions with amine group, but the same behavior was not seen for 4-nitroanisole. Therefore, shift wavelengths of 4-nitroaniline in binary mixtures are noticeable, which were seen in experimental works. In addition, MD simulations were applied to understand the structural analysis of [N4444][Gly] and solvent–solvent interactions and it showed the distances and good probabilities for hydrogen bond interactions between the glycinate and butanol. Finally, QM calculations confirmed both the experimental and MD simulation findings.