The properties of residual water molecules in ionic liquids: a comparison between direct and inverse Kirkwood-Buff approaches.
The properties of residual water molecules in ionic liquids: a comparison between direct and inverse Kirkwood-Buff approaches.
复制标题
DOI：
10.1039/c7cp03717a
复制
发表时间：
2017-07
期刊：
影响因子：
--
通讯作者：
Takeshi Kobayashi;J. Reid;S. Shimizu;M. Fyta;Jens Smiatek
中科院分区：
文献类型：
--
作者：
Takeshi Kobayashi;J. Reid;S. Shimizu;M. Fyta;Jens Smiatek
采用原子分子动力学（MD）模拟方法研究了二烷基咪唑类离子液体1-乙基-3-甲基咪唑四氟硼酸盐（EMIM/BF 4）和1-丁基-3-甲基咪唑四氟硼酸盐（BMIM/BF 4）中不同摩尔分数下残余水分子的性质.通过直接计算径向分布函数，计算了水-离子和离子-离子关联行为的相应Kirkwood-Buff（KB）积分。的结果进行了比较，相应的KB积分的基础上的实验数据的逆方法。我们的研究结果揭示了这两种方法之间的定量协议，这为模拟和实验结果之间更可靠的比较铺平了道路。模拟结果进一步强调，即使在中间摩尔分数的水在溶液中的离子分布的影响可以忽略不计。局部/体积分配系数和部分结构因子的更详细的分析表明，在低摩尔分数的水分子主要保持在单体状态。在较大的水浓度下，可以发现高阶水团簇的非线性增加。对于两种离子液体，可以观察到与阴离子相比，阳离子周围的水配位更明显，这指出离子液体阳离子主要负责水配对机制。因此，我们的模拟提供了详细的见解，在二烷基咪唑离子液体的性质和它们对水结合的影响。
We study the properties of residual water molecules at different mole fractions in dialkylimidazolium based ionic liquids (ILs), namely 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM/BF4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM/BF4) by means of atomistic molecular dynamics (MD) simulations. The corresponding Kirkwood-Buff (KB) integrals for the water-ion and ion-ion correlation behavior are calculated by a direct evaluation of the radial distribution functions. The outcomes are compared to the corresponding KB integrals derived by an inverse approach based on experimental data. Our results reveal a quantitative agreement between both approaches, which paves a way towards a more reliable comparison between simulation and experimental results. The simulation outcomes further highlight that water even at intermediate mole fractions has a negligible influence on the ion distribution in the solution. More detailed analysis on the local/bulk partition coefficients and the partial structure factors reveal that water molecules at low mole fractions mainly remain in the monomeric state. A non-linear increase of higher order water clusters can be found at larger water concentrations. For both ILs, a more pronounced water coordination around the cations when compared to the anions can be observed, which points out that the IL cations are mainly responsible for water pairing mechanisms. Our simulations thus provide detailed insights in the properties of dialkylimidazolium based ILs and their effects on water binding.