|
Fig. 1 |
|
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Fig. 2 The Raman CH2 rocking spectra of pure [bmim][X] (X =PF6, NO3 , BF4, SCN, and CH3COO) at 298 K. The “CH2 r” and “PF6 str” represent the CH2 rocking mode and PF6 stretching mode, respectively. |
 |
Fig. 3. Plots of IGT/ITT of the [bmim]+ cation versus (a) ionic radius of anions except the CH3COO anion, and (b) the order of IGT/ITTfor anions of pure [bmim][X] ([X]= CH3COO, NO3, SCN, PF6, and BF4). |
 |
Fig. 4. Representative Raman CH2 rocking spectra of (a) [bmim][SCN] and (b) [bmim][NO3] as a function of temperature. |
 |
Fig. 5. Temperature dependences of the integrated intensity ratio between the TT and GT conformers of [bmim]+ cation of pure [bmim][X] (X = BF4 (), NO3 (), SCN (), and CH3COO ()). The straight lines represent the result of the least-squares analysis. |
References
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[13] J. N. A. C. Lopes and A. A. H. P´adua, “Using spectroscopic data on imidazolium cation conformations to test a molecular force field for ionic liquids,” Journal of Physical Chemistry B, vol. 110, no. 14, pp. 7485-7489, 2006.
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[15] F. Hofmeister, “Zur Lehre von der Wirkug der Salze,” Archiv for Experimentelle Pathologie und Pharmakologie, vol. 24, pp. 247-269, 1888.
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[17] H. Zhao, O. Olubajo, Z. Song et al., “Effect of kosmotropicity of ionic liquids on the enzyme stability in aqueous solutions,” Bioorganic Chemistry, vol. 34, no. 1, pp. 15-25, 2006.
[18] W. Kunz, P. Lo Nostro, and B. W. Ninham, “The present state of affairs with Hofmeister effects,” Current Opinion in Colloid and Interface Science, vol. 9, no. 1-2, pp. 1-18, 2004.
[19] T. Takekiyo, M. Kato, and Y. Taniguchi, “FT-IR spectroscopic study on conformational equilibria of [Leu]5-enkephalin in DMSO and 2H2O solutions,” Journal of Molecular Liquids, vol. 119, no. 1.3, pp. 147-152, 2005.
[20] Y. Jeon, J. Sung, C. Seo et al., “Structures of ionic liquids with different anions studied by infrared vibration spectroscopy,” Journal of Physical Chemistry B, vol. 112, no. 15, pp. 4735-4740, 2008.
[2] H. Hamaguchi and R. Ozawa, “Structure of ionic liquids and ionic liquid compounds: are ionic liquids genuine liquids in the conventional sense?” Advances in Chemical Physics, vol. 131, pp. 85-104, 2005.
[3] H. Katayanagi, S. Hayashi, H. Hamaguchi, and K. Nishikawa, “Structure of an ionic liquid, 1-n-butyl-3-methylimidazolium iodide, studied by wide-angle X-ray scattering and Raman spectroscopy,” Chemical Physics Letters, vol. 392, no. 4.6, pp. 460-464, 2004.
[4] M. Imanari, M. Nakakoshi, H. Seki, and K. Nishikawa, “1H NMR study on reorientational dynamics of an ionic liquid, 1-butyl-3-methylimidazolium bromide, accompanied with phase transitions,” Chemical Physics Letters, vol. 459, no. 1.6, pp. 89.93, 2008.
[5] T. Endo, T. Kato, K. Tozaki, and K. Nishikawa, “Phase behaviors of room temperature ionic liquid linked with cation conformational changes: 1-Butyl-3-methylimidazolium hexafluorophosphate,” Journal of Physical Chemistry B, vol. 114, no. 1, pp. 407-411, 2010.
[6] R. W. Berg, “Raman spectroscopy and ab-initio model calculations on ionic liquids,” Monatshefte f¨ur Chemie, vol. 138, no. 11, pp. 1045-1075, 2007.
[7] R. Ozawa, S. Hayashi, S. Saha, A. Kobayashi, and H. Hamaguchi, “Rotational isomerism and structure of the 1-butyl-3- methylimidazolium cation in the ionic liquid state,” Chemistry Letters, vol. 32, no. 10, pp. 948-949, 2003.
[8] Y. Umebayashi, T. Fujimori, T. Sukizaki et al., “Evidence of conformational equilibrium of 1-ethyl-3-methylimidazolium in its ionic liquid salts: Raman spectroscopic study and quantum chemical calculations,” Journal of Physical Chemistry A, vol. 109, no. 40, pp. 8976-8982, 2005.
[9] N. E. Heimer, R. E.Del Sesto, Z. Meng, J. S.Wilkes, andW. R. Carper, “Vibrational spectra of imidazolium tetrafluoroborate ionic liquids,” Journal of Molecular Liquids, vol. 124, no. 1.3, pp. 84-95, 2006.
[10] R. Holomb, A. Martinelli, I. Albinsson, J. C. Lass`egues, P. Johansson, and P. Jacobsson, “Ionic liquid structure: the conformational isomerism in 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4]),” Journal of Raman Spectroscopy, vol. 39, no. 7, pp. 793-805, 2008.
[11] Y. U. Paulechka, G. J. Labo, and V. N. Emel’yanenko, “Structure, conformations, vibrations, and ideal-gas properties of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic pairs and constituent ions,” Journal of Physical Chemistry B, vol. 112, no. 49, pp. 15708-15717, 2008.
[12] Y. Umebayashi, H. Hamano, S. Tsuzuki et al., “Dependence of the conformational isomerism in 1-n-butyl-3-methylimidazolium ionic liquids on the nature of the halide anion,” Journal of Physical Chemistry B, vol. 114, no. 36, pp. 11715-11724, 2010.
[13] J. N. A. C. Lopes and A. A. H. P´adua, “Using spectroscopic data on imidazolium cation conformations to test a molecular force field for ionic liquids,” Journal of Physical Chemistry B, vol. 110, no. 14, pp. 7485-7489, 2006.
[14] T. Takekiyo, Temperature and pressure effects on the conformational equilibria of model compounds of proteins in aqueous solutions: a vibrational spectroscopy, Ph.D. thesis, Ritumeikan Univerisity, Shiga, Japan, 2005.
[15] F. Hofmeister, “Zur Lehre von der Wirkug der Salze,” Archiv for Experimentelle Pathologie und Pharmakologie, vol. 24, pp. 247-269, 1888.
[16] Y. Zhang and P. S. Cremer, “Interactions between macromolecules and ions: the Hofmeister series,” Current Opinion in Chemical Biology, vol. 10, no. 6, pp. 658-663, 2006.
[17] H. Zhao, O. Olubajo, Z. Song et al., “Effect of kosmotropicity of ionic liquids on the enzyme stability in aqueous solutions,” Bioorganic Chemistry, vol. 34, no. 1, pp. 15-25, 2006.
[18] W. Kunz, P. Lo Nostro, and B. W. Ninham, “The present state of affairs with Hofmeister effects,” Current Opinion in Colloid and Interface Science, vol. 9, no. 1-2, pp. 1-18, 2004.
[19] T. Takekiyo, M. Kato, and Y. Taniguchi, “FT-IR spectroscopic study on conformational equilibria of [Leu]5-enkephalin in DMSO and 2H2O solutions,” Journal of Molecular Liquids, vol. 119, no. 1.3, pp. 147-152, 2005.
[20] Y. Jeon, J. Sung, C. Seo et al., “Structures of ionic liquids with different anions studied by infrared vibration spectroscopy,” Journal of Physical Chemistry B, vol. 112, no. 15, pp. 4735-4740, 2008.
Last Modified: Nov. 1, 2011