Analytical Sciences
Online ISSN : 1348-2246
Print ISSN : 0910-6340
ISSN-L : 0910-6340
Original Papers
Local Structures of Water in 1-Butyl-3-methylimidazolium Tetrafluoroborate Probed by High-Pressure Infrared Spectroscopy
Hai-Chou CHANGJyh-Chiang JIANGYou-Chang LIOUChao-Hsin HUNGTing-Yun LAISheng Hsien LIN
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2008 Volume 24 Issue 10 Pages 1305-1309

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Abstract

We have investigated the aggregation behaviors of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures using high-pressure methods. Under ambient pressure, the IR spectra indicate that two types of O-H species: free O-H and bonded O-H, existing in ionic liquid/water mixtures. As samples were compressed, a continuous loss of the free O-H band intensity was observed. This observation may have arisen from changes in the local structures of water molecules, and the geometrical properties of the hydrogen-bond network are likely to be perturbed as the pressure is elevated. A complementary insight of the O-H spectral features is obtained by measuring the concentration-dependent variation in the mid-infrared spectra under high pressure. A sharp O-H stretching band was observed in a diluted mixture corresponding to the high order in an ice VII-like structure. Nevertheless, a very broad O-H feature was measured in a concentrated mixture, which may be attributed to the presence of more than one stable cluster.

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© 2008 by The Japan Society for Analytical Chemistry
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