Li Xiaoning, Guo Wenli, Wu Yibo, Li Wei, Gong Liangfa, Zhang Xiaoqian, Li Shuxin, Shang Yuwei, Yang Dan, Wang Hao
College of Material Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.
Department of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing, 102617, China.
J Mol Model. 2018 Mar 6;24(4):83. doi: 10.1007/s00894-018-3586-y.
To identify ionic liquids (ILs) that could be used as solvents in isobutylene (IB) polymerization, the interactions between IB and eight different ILs based on the 1-butyl-3-methylimidazolium cation ([Bmim]) were investigated using density functional theory (DFT). The anions in the ILs were chloride, hexafluorophosphate, tetrafluoroborate, bis[(trifluoromethyl)sulfonyl]imide, tetrachloroaluminate ([AlCl]), tetrachloroferrate, acetate, and trifluoroacetate. The interaction geometries were explained by changes in the total energy, intermolecular distances, Hirshfeld charges, and the electrostatic potential surface. The IL solvents were screened by comparing their interaction intensities with IB to the interaction intensities of reference ILs ([AlCl]-based ILs) with IB. The microscopic mechanism for IB dissolution was rationalized by invoking a previously reported microscopic mechanism for the dissolution of gases in ILs. Computation results revealed that hydrogen (H) bonding between C2-H on the imidazolium ring and the anions plays a key role in ion pair (IP) formation. The addition of IB leads to slight changes in the dominant interactions of the IP. IB molecules occupied cavities created by small angular rearrangements of the anions, just as CO does when it is dissolved in an IL. The limited total free space in the ILs and the much larger size of IB than CO were found to be responsible for the poor solubility of IB compared with that of CO in the ILs.
为了确定可用于异丁烯（IB）聚合反应的离子液体（ILs），利用密度泛函理论（DFT）研究了IB与8种基于1-丁基-3-甲基咪唑阳离子（[Bmim]）的不同离子液体之间的相互作用。离子液体中的阴离子分别为氯离子、六氟磷酸根、四氟硼酸根、双（三氟甲基）磺酰亚胺、四氯铝酸根（[AlCl]）、四氯铁酸根、醋酸根和三氟醋酸根。通过总能量、分子间距离、Hirshfeld电荷和静电势表面的变化来解释相互作用几何结构。通过比较离子液体与IB的相互作用强度和参考离子液体（基于[AlCl]的离子液体）与IB的相互作用强度来筛选离子液体溶剂。通过引用先前报道的气体在离子液体中溶解的微观机制，对IB溶解的微观机制进行了合理化解释。计算结果表明，咪唑环上的C2-H与阴离子之间的氢键在离子对（IP）形成中起关键作用。IB的加入导致离子对主要相互作用的轻微变化。IB分子占据了由阴离子小角度重排形成的空穴，就像CO溶解在离子液体中时那样。发现离子液体中有限的总自由空间以及IB比CO大得多的尺寸是导致IB在离子液体中的溶解度比CO差的原因。
