Effects of water and methanol on the molecular organization of 1-butyl-3-methylimidazolium tetrafluoroborate as functions of pressure and concentration

Hai-Chou Chang, Jyh Chiang Jiang, You-Chang Liou, Chao-Hsin Hung, Ting-Yun Lai, Sheng Hsien Lin

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Abstract

The structural organization in mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])/water or methanol was studied by infrared spectroscopy. No drastic change in the concentration dependence of the alkyl C-H band frequency was observed at high concentration of the ionic liquid. This behavior indicates a clustering of the ionic liquid in alkyl regions. Nevertheless, the presence of methanol significantly perturbs the ionic liquid-ionic liquid associations in the imidazolium region. On the basis of the responses to change in pressure and concentration, two different types of O-H species, i.e., free O-H and bonded O-H, were observed in the O-H stretching region. For [bmim][BF4]/water mixtures, the compression leads to loss of the free O-H band intensity. It is likely that free O-H is switched to bonded O-H as high pressures are applied. For [bmim][BF4]/methanol mixtures, the free O-H is still stable under high pressures. (C) 2008 American Institute of Physics.
Original languageEnglish
Article number044506
JournalJournal of Chemical Physics
Volume129
Issue number4
DOIs
StatePublished - 28 Jun 2008

Keywords

  • TEMPERATURE IONIC LIQUIDS; DOT-O INTERACTIONS; INFRARED-SPECTROSCOPY; HYDROGEN-BONDS; HEXAFLUOROPHOSPHATE; RAMAN; SOLVATION; DIFFUSION; MIXTURES; SOLVENT

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