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Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Methanol, Acetonitrile, and Dimethyl Sulfoxide: A Combined Study of Femtosecond Raman-Induced Kerr Effect Spectroscopy and Molecular Dynamics Simulations.
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-08-12 , DOI: 10.1021/acs.jpcb.0c04870 Masatoshi Ando 1 , Masahiro Kawano 2 , Atsuya Tashiro 2 , Toshiyuki Takamuku 3 , Hideaki Shirota 1
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-08-12 , DOI: 10.1021/acs.jpcb.0c04870 Masatoshi Ando 1 , Masahiro Kawano 2 , Atsuya Tashiro 2 , Toshiyuki Takamuku 3 , Hideaki Shirota 1
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In this study, we examined the low-frequency spectra of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) mixtures with methanol (MeOH), acetonitrile (MeCN), and dimethyl sulfoxide (DMSO), which were obtained by femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and molecular dynamics (MD) simulations. In addition, we estimated the liquid properties of the mixtures, such as density ρ, surface tension γ, viscosity η, and electrical conductivity σ. The line shapes of the low-frequency Kerr spectra of the three [MOIm][BF4] mixture systems strongly depend on the mole fraction of the molecular liquid, XML. The spectral intensity increases with increasing XML of the [MOIm][BF4]/MeCN system but decreases for the [MOIm][BF4]/MeOH and [MOIm][BF4]/DMSO systems. These behaviors of the spectral intensities reasonably agree with the vibrational density-of-states spectra when the polarizability anisotropies of MeOH, MeCN, DMSO, and ion species are considered. The characteristic frequencies (first moments, M1) of the low-frequency spectra of the three mixture systems are almost insensitive at XML = 0–0.6. However, the frequencies vary mildly at XML = 0.6–0.9 and dramatically at XML = 0.9–1. The XML-dependent M1 in the Kerr spectra are well reproduced by the MD simulations. Plots of M1 versus bulk parameter, (γ/ρ)1/2, for the three mixture systems show that the mixtures at XML = 0–0.6 behave like aromatic cation-based ionic liquids (ILs), those at XML = 0.9–1 are molecular liquids (MLs), and those at XML = 0.6–0.9 are transitioning between aromatic cation-based ILs and MLs. MD simulations show that the solvent molecules localized at the interface between the ionic and the alkyl group regions without forming large solvent networks at XML = 0–0.6. However, solvent networks or regions develop largely at XML = 0.6–0.9 and the constituent ions of the IL disperse in the MLs at XML = 0.9–1. The MD simulations corroborate the results obtained by fs-RIKES.
中文翻译：
1-甲基-3-辛基咪唑四氟硼酸酯与甲醇，乙腈和二甲基亚砜混合物的低频光谱：飞秒拉曼诱导的Kerr效应光谱和分子动力学模拟的组合研究。
在这项研究中，我们研究了四氟硼酸1-甲基-3-辛基咪唑鎓（[MOIm] [BF 4 ]）与甲醇（MeOH），乙腈（MeCN）和二甲基亚砜（DMSO）的混合物的低频光谱，通过飞秒拉曼诱导的Kerr效应光谱（fs-RIKES）和分子动力学（MD）模拟获得。另外，我们估计了混合物的液体性质，例如密度ρ，表面张力γ，粘度η和电导率σ。三种[MOIm] [BF 4 ]混合体系的低频Kerr光谱的线形强烈依赖于分子液体X ML的摩尔分数。光谱强度随着[MOIm] [BF 4的X ML的增加而增加] / MeCN系统，但对于[MOIm] [BF 4 ] / MeOH和[MOIm] [BF 4 ] / DMSO系统降低。当考虑MeOH，MeCN，DMSO和离子物种的极化率各向异性时，光谱强度的这些行为与态振动密度谱合理地吻合。在X ML = 0–0.6时，三个混合系统的低频频谱的特征频率（第一矩M 1）几乎不敏感。但是，频率在X ML = 0.6–0.9时变化很小，在X ML = 0.9–1时变化很大。的X ML依赖性中号1MD模拟可以很好地再现Kerr光谱中的。对于三个混合系统，M 1与体积参数（γ/ρ）1/2的关系图表明，在X ML = 0–0.6时，混合物的行为类似于基于芳香族阳离子的离子液体（ILs），而在X ML = 0.9–1是分子液体（MLs），而X ML = 0.6–0.9的分子液体在基于芳族阳离子的IL和ML之间过渡。MD模拟表明，溶剂分子位于离子和烷基区域之间的界面，而在X ML处未形成较大的溶剂网络= 0–0.6。但是，溶剂网络或区域主要在X ML = 0.6–0.9处发展，IL的组成离子在X ML = 0.9–1时分散在ML中。MD模拟证实了fs-RIKES获得的结果。
更新日期：2020-09-10
中文翻译：
1-甲基-3-辛基咪唑四氟硼酸酯与甲醇，乙腈和二甲基亚砜混合物的低频光谱：飞秒拉曼诱导的Kerr效应光谱和分子动力学模拟的组合研究。
在这项研究中，我们研究了四氟硼酸1-甲基-3-辛基咪唑鎓（[MOIm] [BF 4 ]）与甲醇（MeOH），乙腈（MeCN）和二甲基亚砜（DMSO）的混合物的低频光谱，通过飞秒拉曼诱导的Kerr效应光谱（fs-RIKES）和分子动力学（MD）模拟获得。另外，我们估计了混合物的液体性质，例如密度ρ，表面张力γ，粘度η和电导率σ。三种[MOIm] [BF 4 ]混合体系的低频Kerr光谱的线形强烈依赖于分子液体X ML的摩尔分数。光谱强度随着[MOIm] [BF 4的X ML的增加而增加] / MeCN系统，但对于[MOIm] [BF 4 ] / MeOH和[MOIm] [BF 4 ] / DMSO系统降低。当考虑MeOH，MeCN，DMSO和离子物种的极化率各向异性时，光谱强度的这些行为与态振动密度谱合理地吻合。在X ML = 0–0.6时，三个混合系统的低频频谱的特征频率（第一矩M 1）几乎不敏感。但是，频率在X ML = 0.6–0.9时变化很小，在X ML = 0.9–1时变化很大。的X ML依赖性中号1MD模拟可以很好地再现Kerr光谱中的。对于三个混合系统，M 1与体积参数（γ/ρ）1/2的关系图表明，在X ML = 0–0.6时，混合物的行为类似于基于芳香族阳离子的离子液体（ILs），而在X ML = 0.9–1是分子液体（MLs），而X ML = 0.6–0.9的分子液体在基于芳族阳离子的IL和ML之间过渡。MD模拟表明，溶剂分子位于离子和烷基区域之间的界面，而在X ML处未形成较大的溶剂网络= 0–0.6。但是，溶剂网络或区域主要在X ML = 0.6–0.9处发展，IL的组成离子在X ML = 0.9–1时分散在ML中。MD模拟证实了fs-RIKES获得的结果。
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