Using solvatochromic probes to investigate intermolecular interactions in 1,4-dioxane/methanol/acetonitrile solvent mixtures

UV–Vis absorption spectra of five solvatochromic probes namely, betaine (30), 4-nitrophenol, 4-nitroanisole, 4-nitroaniline and N,N-dimethyl-4-nitroaniline, were obtained at 298.15 K in the binary systems 1,4-dioxane/methanol (MeOH) and 1,4-dioxane/acetonitrile (MeCN), and in the ternary system 1,4-dioxane/methanol/acetonitrile, in a total of 40 new solvent mixtures. Preferential solvation trends were assessed through the Bosch and Rosès formalism for the binary mixtures, and the extended model approach for the ternary mixture, thus allowing the setting up of a preferential solvation order for all entities present in solution, including solvent “complexes”. Synergistic behaviors were spotted in most binary mixtures involving 1,4-dioxane but not in the ternary system which is dominated by a combination of contributions from the three underlying binary mixtures. Kamlet-Taft parameters π*, α and β were also computed for all 40 systems and their variation with composition was thoroughly examined. The addition of small amounts of 1,4-dioxane to the mixtures was seen to cause a significant variation in π*, whereas on the other extreme, in dioxane rich mixtures, a large effect in α was observed, particularly for the system 1,4-dioxane/methanol.