Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (08): 1618-1622.doi: 10.3866/PKU.WHXB201305272


Effect of the Ratio between Ionic Liquids [BMIM]Br and [BMIM][BF4] on the Charge Transfer of Br-

MA Jing-Yuan, ZOU Yang, JIANG Zheng, HUANG Yu-Ying   

  1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, P. R. China
  • Received:2013-03-25 Revised:2013-05-24 Published:2013-07-09
  • Contact: HUANG Yu-Ying
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (11079007, 11005148, 10705046) and Funds of the Chinese Academy of Sciences for Key Topics in Innovation Engineering (KJCX2-YW-N43).


We analyzed the change of hydrogen bonding between Br- and imidazolium cations when the ionic liquid 1-butyl-3-methylimidazolium bromide ([BMIM]Br) was gradually mixed with 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIM] [BF4]) using X-ray absorption fine structure (XAFS) and ultraviolet absorption spectroscopies. As the content of [BMIM][BF4] increased, the intensity of the K-edge main peak of Br reduced in X-ray absorption near edge structure (XANES) spectra, and the absorption edge moved 0.9 eV to lower energy. Meanwhile, the radial structure given by extended X-ray absorption fine structure (EXAFS) indicated that the distribution number reduced and average hydrogen bond length increased. UV spectra showed a clear blue shift and peaks decreased in intensity as the content of [BMIM][BF4] increased. All of these results indicate that more negative charge was transferred to Br- as the content of [BMIM][BF4] increased. The data obtained from quantum chemical calculations also support this conclusion.

Key words: Ionic liquid, Charge transfer, X-ray absorption fine structure spectroscopy, Absorption edge, UV spectroscopy


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