A comparison of ether- and alkyl-derivatized imidazolium-based room-temperature ionic liquids: a molecular dynamics simulation study.
A comparison of ether- and alkyl-derivatized imidazolium-based room-temperature ionic liquids: a molecular dynamics simulation study.
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DOI：
10.1039/b808303g
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发表时间：
2008-11
期刊：
影响因子：
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通讯作者：
Grant D. Smith;O. Borodin;Liyong Li;Hojin Kim;Qin Liu;J. Bara;D. Gin;Richard Nobel
中科院分区：
文献类型：
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作者：
Grant D. Smith;O. Borodin;Liyong Li;Hojin Kim;Qin Liu;J. Bara;D. Gin;Richard Nobel
对醚衍生咪唑类室温离子液体[C（5）O（2）mim][TFSI]和[C（5）O（2）mim][BF（4）]进行了分子动力学模拟，并与烷基衍生类似物（ADI-RTIL）的模拟进行了比较.模拟产生RTIL密度，自扩散系数和粘度与实验数据非常吻合。模拟结果表明，在EDI-RTIL的结构，量化的尾部以及阳离子-离子和阳离子-阳离子的相关性的纳米级隔离的程度，减少相比，在ADI-RTIL中观察到的。EDI-RTIL中醚尾氧原子与咪唑环氢原子之间存在显著的相关性。这种相关性主要是分子内的起源，但有一个显着的分子间的组成部分。发现醚氧原子与TFSI（-）的氧原子或BF（4）（-）的氟原子竞争环氢原子的配位，与ADI-RTIL相比，EDI-RTIL中的阳离子-阴离子相关程度降低。分子间相关性的降低，特别是尾-尾分离，以及由于醚尾导致的阳离子-阴离子特异性相互作用的减弱，可以解释EDI-RTIL中观察到的比ADI-RTIL更快的动力学。
Molecular dynamics simulations of ether-derivatized imidazolium-based room-temperature ionic liquids (EDI-RTILs), [C(5)O(2)mim][TFSI] and [C(5)O(2)mim][BF(4)], have been performed and compared with simulations of alkyl-derivatized analogues (ADI-RTILs). Simulations yield RTIL densities, self-diffusion coefficients and viscosity in excellent agreement with experimental data. Simulations reveal that structure in the EDI-RTILs, quantified by the extent of nanoscale segregation of tails as well as cation-ion and cation-cation correlations, is reduced compared to that observed in the ADI-RTILs. Significant correlation between ether tail oxygen atoms and imidazolium ring hydrogen atoms was observed in the EDI-RTILs. This correlation is primarily intramolecular in origin but has a significant intermolecular component. Competition of ether oxygen atoms with oxygen atoms of TFSI(-) or fluorine atoms of BF(4)(-) for coordination of the ring hydrogen atoms was found to reduce the extent of cation-anion correlation in the EDI-RTILs compared to the ADI-RTILs. The reduction in intermolecular correlation, particularly tail-tail segregation, as well as weakening of cation-anion specific interactions due to the ether tail, may account for the faster dynamics observed in the EDI-RTILs compared to ADI-RTILs.