Ultrafast Dynamics in 1-Butyl-3-methylimidazolium-Based Ionic Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study

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• 作者：Hiroki Fukazawa ; Tateki Ishida ; Hideaki Shirota
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：April 28, 2011
• 年：2011
• 卷：115
• 期：16
• 页码：4621-4631
• 全文大小：1167K
• 年卷期：v.115,no.16(April 28, 2011)
• ISSN：1520-5207

文摘

We investigated the ultrafast dynamics in 1-butyl-3-methylimidazolium-based ionic liquids with two series of anions, (1) cyano-group substituted anions (thiocyanate [SCN]^{鈭?/sup>, dicyanamide [N(CN)₂]鈭?/sup>, and tricyanomethide [C(CN)₃]鈭?/sup>) and (2) trifluoromethylsulfonyl-group substituted anions (trifluoromethanesulfonate [OTf]鈭?/sup>, bis(trifluoromethylsulfonyl)amide [NTf₂]鈭?/sup>, and tris(trifluoromethylsulfonyl)methide [CTf₃]鈭?/sup>). This was done by femtosecond Raman-induced Kerr effect spectroscopy. From the Fourier transform Kerr spectra of the ionic liquids, the low-frequency spectrum of 1-butyl-3-methylimidazolium tricyanomethide shows a low-frequency shift compared to the ILs with the other cyano-group substituted anions due to the planar structures of the cation and the anion. The relative amplitude of the low-frequency band at approximately 20 cm鈭? compared to the entire broad spectrum for the ionic liquids with trifluoromethylsulfonyl-group substituted anions becomes larger with the order [OTf]鈭?/sup> < [NTf₂]鈭?/sup> 鈮?[CTf₃]鈭?/sup>. This vibrational band can be attributed to the librational motion of anions and/or the coupling of the translational and reorientational motions.}