title: Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy.
abstract: Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.
authors.affiliation: Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea.
authors.forename: Yoonnam
authors.initials: Y
authors.lastname: Jeon
authors.forename: Jaeho
authors.initials: J
authors.lastname: Sung
authors.forename: Doseok
authors.initials: D
authors.lastname: Kim
authors.forename: Chungwon
authors.initials: C
authors.lastname: Seo
authors.forename: Hyeonsik
authors.initials: H
authors.lastname: Cheong
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ouchi
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Ozawa
authors.forename: Hiro-o
authors.initials: HO
authors.lastname: Hamaguchi
mesh_terms: D001881:Borates / Q000737:chemistry*; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000379:methods; D014867:Water / Q000737:chemistry*
chemical_list: C419324:1-butyl-3-methylimidazolium tetrafluoroborate; D001881:Borates; D007093:Imidazoles; D014867:Water