Switching Of Hydrogen Bonds Of Water In Ionic Liquid, 1-Butyl-3-Methylimidazolium Tetrafluoroborate

We have investigated temperature-induced Raman spectral changes of deuterated water in an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), between room temperature and 77K. The comparison of the OH and OD stretching vibrational spectra at 77K shows that the strength of the hydrogen bonds in [bmim][BF4]water mixtures strongly depends on the type of water, i.e. H2O and D2O. In the [bmim][BF4]D2O system, remarkably strong hydrogen bonds form at low temperatures, but they switch to nearly free hydrogen bonds on heating. Copyright (c) 2013 John Wiley & Sons, Ltd.