Insight into the Intermolecular Interactions in Ionic Liquid-Ethanol-Water Mixtures by Near-Infrared Spectroscopy

Abstract

Abstract In this contribution, an insight into the interactions between 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and water/ethanol was offered using the Near-infrared (NIR) technique. It was found that the supermolecular structure of aqueous [Bmim]BF4 solution was destroyed as mole fraction of water surpasses 0.3979. The addition of ethanol is not favorable for water molecules to interacting with C2-H because of the competence of C2-H · · · O interactions with ethanol molecules, as well as the strong hydrogen-bond interactions between the BF4 − and the hydroxyls of the ethanol. Additionally, the most important is that both water and ethanol prefer to form hydrogen bonds with the proton H2 on imidazolium ring, rather than H4 and H5. These information would have important directive significance for studying the aggregation behavior and the structural organization of ILs in molecular solvents.