Pressure- and temperature-induced Raman spectral changes of 1-butyl-3-methylimidazolium tetrafluoroborate

Yusuke Imaia, Takahiro Takekiyob, Hiroshi Abea andYukihiroYoshimurab

aDepartment of Materials Science and Engineering, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan
bDepartment of Applied Chemistry, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan

High Pressure Research 31 (2011) 53-57.

Abstract
In the present study, we have investigated the pressure- and temperature-induced Raman spectral changes of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). [bmim][BF4] did not crystallize at high pressures below 1.4 GPa. Upon compression, spectral changes in the band due to the CH stretching mode of the alkyl chain are larger than those due to the imidazolium ring, indicating that the environment around the alkyl chain is significantly perturbed. On the other hand, the Raman spectral change of [bmim][BF4] upon cooling at ambient pressure is very small and no crystallization occurs down to 113 K.

Fig. 1
Schematic chemical structures of (a) [bmim] cation and (b) [BF4] anion. Numbering of the skeleton atoms is for the [bmim] cation.


Fig. 2
Raman spectral change of [bmim][BF4] as a function of pressure.
Fig. 3.
Wavenumber shift of the CH asymmetric stretching vibration of the terminal CH3 group of the butyl chain of the [bmim] cation as a function of pressure.
Fig. 4.
Comparison of Raman spectra of [bmim][BF4] at various p-Ts.
References
[1] T. Welton, Room-temperature ionic liquids. Solvents for synthesis and catalysis, Chem. Rev. 99 (1999), pp. 2071-2084.
[2] H. Itoh, K. Naka, andY. Chujo, Synthesis of gold nanoparticles modified with ionic liquid based on the imidazolium cation, J. Am. Chem. Soc. 126 (2004), pp. 3026-3027.
[3] T. Sato, G. Matsuda, and K. Takagi, Electrical properties of novel ionic liquids for electric double layer capacitor applications, Electrochim. Acta. 49 (2004), pp. 3603-3611.
[4] M. GaliLnski, A. Lewandowski, and I. Stepniak, Ionic liquids as electrolytes, Electrochim. Acta, 51 (2006), pp. 5567-5580.
[5] G. Raabe and J. Koehler, Thermodynamical and structural properties of imidazolium based ionic liquids from molecular simulation, J. Chem. Phys. 128 (2008), pp. 154509-1-7.
[6] D. Xiao, J.R. Rajian, A. Cady, S.F. Li, R.A. Bartsch, and E.L. Quitevis, Nanostructural organization and anion effects on the temperature dependence of the optical Kerr effect spectra of ionic liquids, J. Phys. Chem. B 111 (2007), pp. 4669-4677.
[7] Y.T. Wang and G.A. Voth, Unique spatial heterogeneity in ionic liquids, J. Am. Chem. Soc. 127 (2005), pp. 12192-12193.
[8] J.N.A.C. Lopes and A.A.H. Padua, Nanostructural organization in ionic liquids, J. Phys. Chem. B 110 (2006), pp. 3330-3335.
[9] A. Triolo, O. Russina, B. Fazio, R. Triolo, and E.D. Cola, Morphology of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids, Chem. Phys. Lett. 457 (2008), pp. 362-365.
[10] Y. Imai, H. Abe, T. Goto, T. Miyashita, and Y. Yoshimura, Pressure-induced change in the Raman spectra of ionic liquid [DEME][BF4] - H2O mixtures, J. Phys. Conf. Ser. 215 (2010), pp. 12069-1-4.
[11] H.K. Mao, P.M. Bell, J.W. Shaner, and D.J. Steinberg, Specific volume measurements of Cu, Mo, Pd, and Ag and calibration of the ruby R1 fluorescence pressure gauge from 0.06 to 1 Mbar, J. Appl. Phys. 49 (1978), pp. 3276-3283.
[12] J. Sung, Y. Jeon, D. Kim, T. Iwahashi, T. Iimori, K. Seki, and Y. Ouchi, Air-liquid interface of ionic liquid + H2O binary system studied by surface tension measurement and sum-frequency generation spectroscopy, Chem. Phys. Lett. 406 (2005), pp. 495-500.
[13] Y. Jeon, J. Sung, D. Kim, C. Seo, H. Cheong,Y. Ouchi, R. Ozawa, and H. Hamaguchi, Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy, J. Phys. Chem. B 112 (2008), pp. 923-928.
[14] H.-C. Chang, J.-C. Jiang, C.-Y. Chang, J.-C. Su, C.-H. Hung, Y.-C. Liou, and S.H. Lin, Structural organization in aqueous solutions of 1-butyl-3-methylimidazolium halides: A high-pressure infrared spectroscopic study on ionic liquids, J. Phys. Chem. B 112 (2008), pp. 4351-4356.
[15] M.E.V.Valkenburg, R.L.Vaughn, M.Williams, and J.S.Wilkes, Thermochemistry of ionic liquid heat-transfer fluids, Thermochim. Acta 425 (2005), pp. 181-188.
[16] J.D. Holbrey and K.R. Seddon, The phase behaviour of 1-alkyl-3-methylimidazolium tetrafluoroborates; ionic liquids and ionic liquid crystals, J. Chem. Soc. Dalton Trans. (1999), pp. 2133-2139.
[17] 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, Chem. Lett. 32 (2003), pp. 948-949.

Last Modified: April 1, 2011