Ultrafast vibrational dynamics and energy transfer in imidazolium ionic liquids.
Ultrafast vibrational dynamics and energy transfer in imidazolium ionic liquids.
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DOI：
10.1021/ja502527y
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发表时间：
2014-04
影响因子：
15
通讯作者：
M. Namboodiri;M. Kazemi;Tahir Zeb Khan;A. Materny;J. Kiefer
中科院分区：
文献类型：
--
作者：
M. Namboodiri;M. Kazemi;Tahir Zeb Khan;A. Materny;J. Kiefer
利用飞秒时间分辨相干反斯托克斯拉曼散射（汽车）作为探针，研究了室温离子液体（IL）的振动动力学。实验在一系列含有双（三氟甲基磺酰基）酰亚胺[NTf 2]阴离子的1，3-二烷基咪唑离子液体上进行。通过分析1-乙基-3-甲基咪唑[EMM]、1-乙基-2，3-二甲基咪唑[EMMIM]、1-丁基-3-甲基咪唑[BMIM]和1-丁基-2，3-二甲基咪唑[BMMIM]的[NTf 2]-IL，研究了阳离子C2位置的甲基化对退相时间的影响。拉曼相干光在1400 cm（-1）附近被激发，并且指纹区域中的模式的振动退相被监测为时间的函数。结果表明，振动能量转移的发生受电子相互作用。这是由涉及超出激发光谱的振动的模式拍频以及时间失相行为中的系统差异所暗示的。相反，阳离子烷基侧链的长度对振动动力学的影响可以忽略不计。
Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) is used as a probe for monitoring the vibrational dynamics of room temperature ionic liquids (ILs). The experiments are performed on a series of 1,3-dialkylimidazolium ILs containing the bis(trifluoromethylsulfonyl)imide [NTf2] anion. The effect of methylation of the cationic C2 position on the dephasing time is studied analyzing [NTf2]-ILs of 1-ethyl-3-methylimidazolium [EMIM], 1-ethyl-2,3-dimethylimidazolium [EMMIM], 1-butyl-3-methylimidazolium [BMIM], and 1-butyl-2,3-dimethylimidazolium [BMMIM]. Raman coherences are excited around ∼1400 cm(-1), and the vibrational dephasing of the modes in the fingerprint region is monitored as a function of time. The results indicate that vibrational energy transfer occurs governed by the interionic interactions. This is suggested by mode beating involving vibrations beyond the excitation spectrum as well as systematic differences in the temporal dephasing behavior. In contrast, the length of the cationic alkyl side chain has a negligible impact on the vibrational dynamics.