Atom substitution effects of [XF6]- in ionic liquids. 1. Experimental study.
Atom substitution effects of [XF6]- in ionic liquids. 1. Experimental study.
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DOI：
10.1021/jp809880j
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发表时间：
2009-06
期刊：
影响因子：
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通讯作者：
H. Shirota;K. Nishikawa;T. Ishida
中科院分区：
文献类型：
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作者：
H. Shirota;K. Nishikawa;T. Ishida
研究了以[PF6]-、[AsF6]-和[SbF6]-为阴离子的1-丁基-3-甲基咪唑阳离子（[BMIm]+）离子液体的离子间振动动力学以及剪切粘度和液体密度等静态物理性质。离子液体的剪切粘度随着原子阴离子的重而降低：[BMIm][PF6]>[BMIm][AsF6]>[BMIm][SbF6]。这种重原子取代阴离子的趋势是由于较大的阴离子体积造成较弱的离子间相互作用。利用飞秒光学外差探测拉曼诱导克尔效应光谱法观察了离子液体的离子间振动动力学。在小于50 cm（-1）的频率区，离子间振动明显表现出重原子取代效应；即[XF6]-的重原子取代严重影响相互作用诱导的运动。即将发表的论文将通过分子动力学模拟方法进一步提供[XF6]-阴离子的重原子取代效应对三种离子液体的离子间动力学和相互作用的分子水平见解。
We have investigated the interionic vibrational dynamics of 1-butyl-3-methylimidazolium cation ([BMIm]+) based ionic liquids with the anions of [PF6]-, [AsF6]-, and [SbF6]- as well as the static physical properties, such as shear viscosity and liquid density. Shear viscosity for the ionic liquids becomes lower with the heavier atom anion: [BMIm][PF6]>[BMIm][AsF6]>[BMIm][SbF6]. This tendency for heavy atom substitution for the anion results from weaker interionic interaction caused by larger anion volume. Femtosecond optically heterodyne-detected Raman-induced Kerr effect spectroscopy has been used to observe the interionic vibrational dynamics of ionic liquids. The interionic vibration in the frequency region of less than 50 cm(-1) clearly shows the heavy atom substitution effect; that is, the heavy atom substitution of [XF6]- critically affects the interaction-induced motion. The forthcoming paper will further provide the molecular-level insights of the heavy atom substitution effect of the [XF6]- anion on the interionic dynamics and interaction for the three ionic liquids by a molecular dynamics simulation approach.