Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy

Yasuhiro Umebayashi, Jyh Chiang Jiang, Kuan-Hung Lin, Yu-Lun Shan, Kenta Fujii, Shiro Seki, Shin-Ichi Ishiguro, Sheng Hsien Lin, Hai-Chou Chang

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Abstract

The microscopic features of binary mixtures formed by an ionic liquid (EMI(+)TFSA(-) or EMI(+)FSA(-)) and a molecular liquid (acetonitrile or methanol) have been investigated by high-pressure infrared spectroscopy. On the basis of its responses to changes in pressure and concentration, the imidazolium C-H appears to exist at least in two different forms, i.e., isolated and associated structures. The weak band at approximately 3102 cm(-1) should be assigned to the isolated structure. CD3CN can be added to change the structural organization of ionic liquids. The compression of an EMI(+)TFSA(-)/CD3CN mixture leads to the increase in the isolated C-H band intensity. Nevertheless, the loss in intensity of the isolated structures was observed for EMI(+)FSA(-)/CD3CN mixtures as the pressure was elevated. In other words, the associated configuration is favored with increasing pressure by debiting the isolated form for EMI(+)FSA(-)/CD3CN mixtures. The stronger C-H center dot F interactions in EMI(+)FSA(-) may be one of the reasons for the remarkable differences in the pressure-dependent results of EMI(+)TFSA(-) and EMI(+)FSA(-).
Original languageEnglish
Article number234502
JournalJournal of Chemical Physics
Volume131
Issue number23
DOIs
StatePublished - 21 Dec 2009

Keywords

  • high-pressure effects; infrared spectra; liquid mixtures; liquid structure; organic compounds; solvation KeyWords Plus:CENTER-DOT-O; 1-BUTYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE; ROTATIONAL RELAXATION; HYDROGEN-BONDS; PAIR FORMATION; TEMPERATURE; LIQUID; WATER; DYNAMICS; COUMARIN-153

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