Solvatochromic Absorbance Probe Behavior within Mixtures of the Ionic Liquid 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide plus Molecular Organic Solvents

The solvent mixtures made up of ionic liquid and molecular solvents have potential applications in various fields such as chemical analysis and synthesis. Thus, in the present study, the role of the solvent microsphere in changing the behavior of the solvatochromic absorbance probe within binary solvent mixtures of ionic liquids with common molecular organic solvents is explored. Further, the behavior of the probes is explained with the help of solute solvent and solvent- solvent interactions present in the mixtures. The binary mixtures of the ionic liquid 1butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf2N], with molecular solvents, polar protic (methanol, 1-butanol) and polar aprotic (dimethyl sulfoxide, and N,N-dimethylformamide), have been selected for this investigation. The effect of the addition of molecular solvents to ionic liquid's polarity parameters, E-T(N), and Kamlet Taft parameters, the hydrogen bond donor ability (HBD) (alpha), hydrogen bond acceptor ability (HBA) (beta), and dipolarity/polarizability (pi*), is investigated. The polarity parameters, E-T(N), and dipolarity/polarizability (pi*) of the mixtures indicate the "hyperpolarity" behavior on addition of molecular solvents to ionic liquid. The preferential solvation model has been used to provide insight on the solvent-solvent and/or solute solvent interactions in the solvent mixtures.