Molecular structure, reorientational dynamics, and intermolecular interactions in the neat ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate
Molecular structure, reorientational dynamics, and intermolecular interactions in the neat ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate
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DOI：
10.1351/pac200476010255
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发表时间：
2004-01-01
影响因子：
1.8
通讯作者：
Carper, WR
中科院分区：
文献类型：
--
作者：
Antony, JH;Mertens, D;Carper, WR
报道了离子液体1-丁基-3-甲基咪唑六氟磷酸盐（[BMIM][PF 6]）的分子结构、液体结构和取向动力学的研究结果。通过对[BMIM][PF 6]在气相中的量子化学计算，发现芳环中碳2上的质子与六氟磷酸根阴离子的氟原子之间存在氢键作用，通过对C-13弛豫数据的分析，计算了[BMIM][PF 6]的再取向运动，并分别计算了[BMIM][PF 6]的整体和内部再取向运动的Vogel-Fulcher-Tammann和Arrhenius活化能。给出了300 K时不同C-13-H-1矢量的关联时间。通过进行分子动力学（MD）模拟，阳离子和阴离子中的磷原子的部分之间的配对分布函数被确定。在碳2的质子的对分布函数表现出一个特别尖锐和强的最大值，表明与阴离子的强相互作用。量子化学计算、分子动力学参数和分子动力学模拟结果均支持离子液体中存在氢键和离子对。
Results on the molecular and liquid structure and the reorientational dynamics are reported for the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). In quantum-chemical calculations for [BMIM][PF6] in the gas phase, hydrogen bonding between the proton at carbon 2 in the aromatic ring and the fluorine atoms of the hexafluorophosphate anion was found. From the analysis of C-13 relaxation data, the reorientational motions were evaluated, and the Vogel-Fulcher-Tammann and Arrhenius activation energies for the overall and internal reorientational motions, respectively, of the different C-13-H-1 vectors are given as well as correlation times at 300 K. By performing molecular dynamics (MD) simulations, pair-distribution functions between moieties in the cation and the phosphorous atom in the anion were determined. The pair-distribution function for the proton at carbon 2 exhibits a particular sharp and strong maximum indicating a strong interaction with the anion. The quantum-chemical calculations, the motional parameters, and the results from the MD simulations support the existence of hydrogen bonding and the formation of ion pairs in the ionic liquid.