How polar are ionic liquids?: Determination of the static dielectric constant of an imidazolium-based ionic liquid by microwave dielectric spectroscopy

被引:487
作者
Wakai, C [1 ]
Oleinikova, A [1 ]
Ott, M [1 ]
Weingärtner, H [1 ]
机构
[1] Ruhr Univ Bochum, D-44780 Bochum, Germany
关键词
D O I
10.1021/jp053946+
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
In a pilot study of the dielectric constant of room-temperature ionic liquids, we use dielectric spectroscopy in the megahertz/gigahertz regime to determine the complex dielectric function of five 1-alkyl-3-methylimidazolium salts, from which the static dielectric constant epsilon is obtained by zero-frequency extrapolation. The results classify the salts as moderately polar solvents. The observed epsilon-values at 298.15 K fall between 15.2 and 8.8, and epsilon decreases with increasing chain length of the alkyl residue of the cation. The anion sequence is trifluoromethylsulfonate > tetrafluoroborate tetrafluorophosphate. The results indicate markedly lower polarities than found by spectroscopy with polarity-sensitive solvatochromic dyes.
引用
收藏
页码:17028 / 17030
页数:3
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