Effect of Ion Rigidity on Physical Properties of Ionic Liquids Studied by Molecular Dynamics Simulation.
Effect of Ion Rigidity on Physical Properties of Ionic Liquids Studied by Molecular Dynamics Simulation.
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DOI：
10.1021/acs.jpcb.6b03379
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发表时间：
2016-06
期刊：
影响因子：
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通讯作者：
P. Ramírez-González;Gan Ren;G. Saielli;Yanting Wang
中科院分区：
文献类型：
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作者：
P. Ramírez-González;Gan Ren;G. Saielli;Yanting Wang
在这项工作中，我们进行了分子动力学（MD）模拟，比较了三种离子液体（IL）的结构和动力学性质：1-乙基-3-甲基-咪唑四氟硼酸盐（[EMI（+）][BF 4（-）]）、1，1 '-二甲基-4，4'-联吡啶双（四氟硼酸盐）（[VIO（2+）][BF 4（-）]2）和1，1 '-二甲基-4，4'-联吡啶鎓双[VIO（2+）][Tf 2N（-）]2），旨在发现离子刚性对离子液体物理性质的影响。[VIO（2+）]比[EMI（+）]刚性更大，[BF 4（-）]比[Tf 2N（-）]刚性更大。[VIO（2+）][BF 4（-）]2的阴离子分布与其他两种不同，其阴阳离子径向分布函数的峰高且尖锐，反映了阴离子在阳离子周围的紧密堆积局部结构。[VIO（2+）][BF 4（-）]2和[VIO（2+）][Tf 2N（-）]2具有比[EMI（+）][BF 4（-）]慢得多的类似动力学，并且[VIO（2+）][Tf 2N（-）]2显示出比[VIO（2+）][BF 4（-）]2和[EMI（+）][BF 4（-）]更各向同性的分子分布。此外，我们模拟了两个修改后的viologen为基础的离子液体，以加强我们的解释。从上述模拟结果中我们得出结论，阴离子的刚性影响阳离子的排列，并且阳离子的刚性对其旋转能力显示出很大的障碍。此外，我们还观察到由于静电相关，[VIO（2+）][BF 4（-）]2的扩散较慢，这稳定了离子笼效应。
In this work, we have performed molecular dynamics (MD) simulations to compare the structural and dynamical properties of three ionic liquids (ILs), 1-ethyl-3-methyl-imidazolium tetrafluorborate ([EMI(+)][BF4(-)]), 1,1'-dimethyl-4,4'-bipyridinium bis(tetrafluorborate) ([VIO(2+)][BF4(-)]2), and 1,1'-dimethyl-4,4'-bipyridinium bis(trifluoromethylsulfonyl)imide (bistriflimide in short) ([VIO(2+)][Tf2N(-)]2), aiming to discover the influence of ion rigidity on the physical properties of ILs. [VIO(2+)] is more rigid than [EMI(+)], and [BF4(-)] is more rigid than [Tf2N(-)]. [VIO(2+)][BF4(-)]2 has an anion distribution different from the other two by the higher and sharper peaks in the cation-anion radial distribution functions, reflecting a close-packed local structure of anions around cations. [VIO(2+)][BF4(-)]2 and [VIO(2+)][Tf2N(-)]2 have similar dynamics much slower than [EMI(+)][BF4(-)], and [VIO(2+)][Tf2N(-)]2 shows a more isotropic molecular distribution than [VIO(2+)][BF4(-)]2 and [EMI(+)][BF4(-)]. Additionally, we have simulated two modified viologen-based ILs to reinforce our interpretations. We conclude from the above simulation results that the rigidity of anions influences the alignment of cations and that the rigidity of cations shows a large obstacle to their rotational capacity. Moreover, we have observed a slower diffusion of [VIO(2+)][BF4(-)]2 due to the electrostatic correlations, which stabilizes the ion-cage effect.