Physicochemical study on molecular interactions in ternary aqueous solutions of the pharmaceutically active ionic liquid cetylpyridinium salicylate and amino acid/glycylglycine at different temperatures

The pharmaceutically active form of an ionic liquid , cetylpyridinium salicylate ([CetPy][Sal]), was synthesized, and the intermolecular interactions of [CetPy][Sal] with amino acids (glycine, L-alanine, L-valine, and L-leucine) and glycylglycine (AAGG) in aqueous media were investigated by measuring the density, conductivity and UV–visible spectra at different temperatures. The measured density data was used to compute the apparent molar volume at infinite dilution, V 2, φ 0 , the hydration number , n H , the transfer volume, ∆ t V 0 , and the apparent molar expansibility at infinite dilution, E   ∅   o , of AAGG in aqueous [CetPy][Sal] solution. The measured electrical conductivity was used to calculate the critical micelle concentration, cmc , and the relative thermodynamic quantities for the micellization of [CetPy][Sal] in an AAGG solution, i.e. the changes in the Gibbs free energy , the enthalpy, and the entropy. The binding constants between [CetPy][Sal] and AAGG were derived from UV–vis spectroscopic data . The aforementioned properties were analyzed in terms of the molecular interactions and structural changes existing in the studied ternary solutions of (AAGG +[CetPy][Sal]+water).