呋喃-乙酸分子间相互作用的量子化学研究

用密度泛函理论B3LYP方法选取6-311＋＋G(d,p)基组对呋喃-乙酸复合物进行了量子化学计算研究, 通过在相同水平下的频率振动分析发现了该势能面上6个极小值点, 其最稳定构型对应一强O…H—O型氢键, 其结合能在消除基组重叠误差后为－20.87 kJ•mol^－1. 通过自然键轨道(NBO)分析, 研究了电荷转移及轨道相互作用. 通过自洽反应场(SCRF)理论中的Onsager 溶剂模型在介电常数分别为1.0, 2.247, 4.9, 7.58, 10.36, 20.7, 32.63, 38.2, 46.7, 78.39的不同溶剂环境下重新优化呋喃与乙酸势能面上最稳定构型A, 研究了溶剂对呋喃-乙酸复合物几何构型、电荷分布、偶极矩以及结合能的影响. 发现溶剂化作用增大了呋喃与乙酸分子间的结合能, 导致O…H距离减小, H—O振动频率红移. 当溶液介电常数在1.0～32.63范围时, 溶剂效应十分显著, 当介电常数大于32.63后, 溶剂化作用几乎达到了极限.

Ab initio Investigation on the Interaction of Furan with Acetic Acid Complexes

Furan and acetic acid 1∶1 complex was subjected to density functional theory calculations using 6-311＋＋G(d,p) basis set. Six equilibrium isomers were located on the potential energy surface. The most stable structure has a strong O…H—O hydrogen-bonding interaction, and the calculated bonding energy of it is －20.87 kJ•mol^－1. A normal-mode analysis of the vibrations of the six isomers was carried out. The solvent effects on the geometries of equilibrium isomers and dipole moments were systematically studied by self-consistent reaction field technique with different dielectric constants of 1.0, 2.247, 4.9, 7.58, 10.36, 20.7, 32.63, 38.2, 46.7 and 78.39. It was found that the solvent effect would enhance significantly the strength of hydrogen bond as shown by the decrease of the O…H distance and appreciable red shift of the H—O vibration mode. The solvent effect was obvious when ε was in 1.0～32.63 and was weak when ε exceeded 32.63.