Analysis of interactions between 1-butyl-3-methylimidazolium cation and halide anions (Cl−, Br− and I−) by ab initio calculations: anion size effects on preferential locations of anions
Analysis of interactions between 1-butyl-3-methylimidazolium cation and halide anions (Cl−, Br− and I−) by ab initio calculations: anion size effects on preferential locations of anions
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DOI：
10.1080/00268970802258575
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发表时间：
2008-06
影响因子：
1.7
通讯作者：
S. Tsuzuki;R. Katoh;M. Mikami
中科院分区：
文献类型：
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作者：
S. Tsuzuki;R. Katoh;M. Mikami
采用MP2/6- 311 G ** 水平从头计算方法，研究了1-丁基-3-甲基咪唑（bmim）和1，3-二甲基咪唑（dmim）与卤阴离子的分子间相互作用能. DGDZVP基组用于碘化物。计算得到的bmim与Cl、Br和I阴离子的络合物的形成能分别为−88.4、−86.4和−79.0 kcal/mol。分布多极分析表明，静电相互作用是吸引力的主要来源。诱导能占总相互作用能的13-21%。静电相互作用主要决定了吸引力的大小和配合物的稳定几何构型。在[bmim]Cl和[bmim]Br配合物的最稳定几何构型中，阴离子位于咪唑平面内，并与bmim的C2-H紧密接触。另一方面，[bmim]I配合物具有另一种几乎等能的几何构型，其中I阴离子位于咪唑平面上方。阴离子的优先位置与晶体中观察到的一致。小的Cl和Br阴离子由于静电相互作用的稳定性而更倾向于位于平面内。由于静电相互作用的各向异性，其中Cl和Br阴离子位于咪唑平面上方或下方的几何形状较不稳定。静电相互作用的各向异性随着距离的增加而迅速减小。因此，大的I阴离子更喜欢这两个位置。
The intermolecular interaction energies for the 1-butyl-3-methylimidazolium (bmim) and 1,3-dimethylimidazolium (dmim) complexes with halide anions were studied using the MP2/6-311G** level ab initio calculations. The DGDZVP basis set was used for iodide. Calculated formation energies for the bmim complexes with Cl, Br and I anions from isolated ions were −88.4, −86.4 and −79.0 kcal/mol, respectively. Distributed multipole analysis shows that the electrostatic interaction is the major source of the attraction. The induction energy is 13–21% of the total interaction energy. The electrostatic interaction mainly determines the magnitude of the attraction and the stable geometries of the complexes. In the most stable geometries for the [bmim]Cl and [bmim]Br complexes, the anion locates within the imidazolium plane and have close contacts with the C2–H of bmim. On the other hand the [bmim]I complex has another nearly isoenergetic geometry, in which the I anion locates above the imidazolium plane. The preferential location of anions agrees well with those observed in the crystals. The small Cl and Br anions prefer to locate within the plane due to the stabilization by the electrostatic interaction. The geometries, in which the Cl and Br anions locate above or below the imidazolium plane, are less stable due to the anisotropy of the electrostatic interaction. The anisotropy of electrostatic interaction decreases rapidly with distance. Therefore the large I anion prefers both locations.