標題: Structural change of ionic association in ionic liquid/water mixtures: A high-pressure infrared spectroscopic study
作者: Umebayashi, Yasuhiro
Jiang, Jyh-Chiang
Shan, Yu-Lun
Lin, Kuan-Hung
Fujii, Kenta
Seki, Shiro
Ishiguro, Shin-Ichi
Lin, Sheng Hsien
Chang, Hai-Chou
應用化學系
Department of Applied Chemistry
關鍵字: association;high-pressure effects;hydrogen bonds;infrared spectra;liquid mixtures;liquid structure;organic compounds;spectral line intensity
公開日期: 28-Mar-2009
摘要: High-pressure infrared measurements were carried out to observe the microscopic structures of two imidazolium-based ionic liquids, i.e., 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [EMI(+)(CF(3)SO(2))(2)N(-), EMI(+)TFSA(-)] and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [EMI(+)(FSO(2))(2)N(-), EMI(+)FSA(-)]. The results obtained at ambient pressure indicate that the imidazolium C-H may exist in two different forms, i.e., isolated and network structures. As the sample of pure EMI(+)FSA(-) was compressed, the network configuration is favored with increasing pressure by debiting the isolated form. For EMI(+)TFSA(-)/H(2)O mixtures, the imidazolium C-H peaks split into four bands at high pressures. The new spectral features at approximately 3117 and 3190 cm(-1), being concentration sensitive, can be attributed to the interactions between the imidazolium C-H and water molecules. The alkyl C-H absorption exhibits a new band at approximately 3025 cm(-1) under high pressures. This observation suggests the formation of a certain water structure around the alkyl C-H groups. The O-H stretching absorption reveals two types of O-H species, i.e., free O-H and bonded O-H. For EMI(+)TFSA(-)/H(2)O mixtures, the compression leads to a loss of the free O-H band intensities, and pressure somehow stabilizes the bonded O-H configurations. The results also suggest the non-negligible roles of weak hydrogen bonds in the structure of ionic liquids.
URI: http://dx.doi.org/10.1063/1.3100099
http://hdl.handle.net/11536/7461
ISSN: 0021-9606
DOI: 10.1063/1.3100099
期刊: JOURNAL OF CHEMICAL PHYSICS
Volume: 130
Issue: 12
結束頁: 
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