Hydrogen-bonding interactions between 1-butyl-2,3-dimethylimidazolium tetrafluoroborate and dimethyl sulphoxide

In practical use, ionic liquids (ILs) often mix with cosolvents to reduce the high polarity, large viscosity and high cost of pure ILs. Hydrogen-bonding interactions greatly influence the properties of IL-cosolvent system. In this work, the interactions between an IL 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BMMIM][BF4]) and DMSO have been investigated by attenuated total reflection infrared (ATR-IR) spectroscopy and density functional theory (DFT) calculations. Excess infrared spectroscopy and twodimensional (2D) correlation infrared spectroscopy were applied to analyze the infrared spectra. It is found that: 1) Hydrogen-bonding interaction is the main cause that induces the infrared spectra change of v(C-H) and v(C-D). 2) The hydrogen-bonding interactions involving C4,5 H change prior to that of the alkyl C H in IBMMIMHBF4]. 3) The hydrogen atoms in the CH3 attached to N3 are more preferred to be hydrogen-bond donors than the other hydrogen atoms in the [BMMIM](+) cation. 4) The hydrogen bonds in the [BMMIM](+)-[BF4](-) and [BMMIM][BF4]-DMSO complexes are the closed shell interaction and are electrostatic dominant. 2018 Elsevier B.V. All rights reserved.