11 different initial structures of 1-(4-aminobutyl)-3-methylimidazolium chloride in gas phase was optimized at B3LYP/ 6-311++G(d,p)level by density functional theory method. Ion-pairs binding energy and second-order perturbation stabilization energy were also obtained at the same level. 8 different stable geometries were confirmed. The biggest energy difference between the geome-tries is 11. 1 kcal·mol-1. The analysis of natural bond orbital and frontier molecular orbitals on the most stable geometry shows that hyperconjugation in the imidazolium ring is caused by the interaction between LP(1)N1 and BD*(2)N4-C5,which results in the stabilization energy with the value of 73. 54 kcal·mol-1. It is because of the orbital symmetry matching thatσ(C-H…Cl)hydrogen bond is formed by the interactions between HOMO of Cl anion and unoccupied σ*orbital of C4 NH2 C1 im cation.%采用密度泛函理论方法B3LYP/6-311++G(d,p)计算了氯化1-(4-氨基丁基)-3-甲基咪唑离子液体气相下几何构型、离子对结合能和二阶微扰稳定化能等.得到了8种不同的稳定结构,不同结构所具有的能量差异最大为11.1 kcal·mol-1.能量最小稳定构型的氯化1-(4-氨基丁基)-3-甲基咪唑自然价键前线轨道分析结果表明:超共轭作用主要发生在咪唑环内,LP(1)N1→BD*(2)N4-C5电子离域引起的稳定化能达73.54 Kcal·mol-1.氯阴离子和1-(4-氨基丁基)-3-甲基咪唑阳离子作用生成氯化1-(4-氨基丁基)-3-甲基咪唑时,轨道对称性匹配占主导作用,阴离子的HOMO轨道与阳离子具有更高能量的非占据 σ*轨道相互作用,形成了 σ型的C-H…Cl氢键.
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