Pressure-induced Change in the Raman Spectra of Ionic Liquid [DEME][BF4]-H2O Mixtures

Y. ImaiA, H. AbeA, T. GotoB, T. MiyashitaB and Y. YoshimuraB

ADepartment of Materials Science and Engineering, National Defense Academy,
Yokosuka, Kanagawa, 239-8686, Japan
BDepartment of Applied Chemistry, National Defence Academy, Yokosuka,
Kanagawa, 239-8686, Japan

Journal of Physics: Conference Series 215 (2010) 012069

Abstract

We have measured Raman spectral changes of N,N,diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF4]-H2O mixtures under high pressure. All the Raman spectra of mixtures of water concentrations below 50.0 mol% H2O changed at around 1 GPa at room temperature. The spectrum at high pressure is completely different from that obtained by cooling the sample at a normal pressure.

Fig. 1.
The CH stretching Raman spectra of [DEME][BF4]-H2O mixed solutions as a function of pressure. Measured temperature is fixed at room temperature.


Fig. 2.
ν1 symmetric mode of H2O corresponding to a nearly free hydrogen bond band (NFHB). Upon compression, the NFHB at around 3550 cm-1 seems to fade away.
Fig. 3.
Raman CH stretching spectra at several concentrations where the pressure-induced structural change occurred are shown. For a comparison, the spectrum of pure [DEME][BF4] at -80 °C at a normal pressure is shown at the bottom of the figure.
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ab@nda.ac.jp
Department of Materials Science and Engineering
National Defense Academy

Last Modified: April 1, 2009