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采用Hartree-Fock和密度泛函理论方法研究1-乙基-3-甲基咪唑阳离子(EMIM+)、PF6-、EMIM+-PF6-离子对。氢原子、碳原子、氮原子、氟原子和磷原子在6-31+(d,p)基组水平上,采用Gaussian94软件包给EMIM+、PF6-及12个EMIM+-PF6-离子的初始结构做全优化和频率分析。比较研究所优化结构和能量的性质。计算结果表明最低能量结构的EMIM+-PF6-阴阳离子对相互作用能,在Hartree-Fock水平上为326.6 kJ／mol、在密度泛函理论上为328.8 kJ／mol。阳离子不对称、阴阳离子间距较大、阴阳离子电荷的分散使①静电作用降低,导致离子液体熔点较低。②EMIM+氢原子的正电荷增加、PF6-氟原子的负电荷增加,导致C-H---F氢键相互作用增强。从而在离子液体中起重要作用。本文着重考察了EMIM+和PF6-相互作用的三种氢键方式。
The 1-ethyl-3-methylimidazolium cation (EMIM +), PF6-, EMIM + -PF6- ion pairs were studied using Hartree-Fock and density functional theory. The original structures of EMIM +, PF6- and 12 EMIM + -PF6- ions were made using the Gaussian94 software package at the 6-31 + (d, p) basis set for hydrogen atoms, carbon atoms, nitrogen atoms, fluorine atoms and phosphorus atoms Full optimization and frequency analysis. Compare the optimal structure and energy properties of the Institute. The calculated results show that the interaction energies of EMIM + -PF6-anion-cation pairs for the lowest energy structure are 326.6 kJ / mol at Hartree-Fock level and 328.8 kJ / mol at density functional theory. Cation asymmetry, the larger the distance between the anion and cation, the dispersion of the charge of the anion and cation so ① electrostatic effect decreases, resulting in a lower melting point of the ionic liquid. ②EMIM + hydrogen atom positive charge increases, PF6-fluorine atom negative charge increases, leading to C-H --- F hydrogen bond interaction enhanced. Thus playing an important role in ionic liquids. This article focuses on the three hydrogen bonding modes of EMIM + and PF6-interactions.