香豆素及其衍生物与CHF_3的团簇的理论研究

Theoretical Study on the Clusters of Coumarin and its Derivative with CHF_3

采用密度泛函理论中的M06-2X方法,以6-311++G(d,p)为基组,对香豆素分子和7-氟-香豆素分子的单体及其分别与三氟甲烷形成的团簇进行了几何构型优化和振动频率计算。结果表明,香豆素及其衍生物分子上具有不同的团簇结合位点,且氟取代基的存在使团簇结合能降低;应用分子中的原子理论(AIM)证明了团簇中的分子间作用是氢键作用;分析团簇的构型结果显示,在CH...X(X=O,F)型团簇中,CHF_3中质子供体C-H键的键长伸长,振动频率蓝移,而在CH…π型团簇中C-H键长和振频的变化没有明显规律。在此基础上,本文采用自然键轨道(NBO)理论对部分体系的氢键形成机理进行了解释,结果表明当重杂化效应占主导时,表现为蓝移氢键。

In this work,the geometry optimization and vibrational frequency calculations were performed for the monomers of coumarin and 7-fluoro-coumarin and their clusters with fluoroform at the M06-2X/6-311 ＋ ＋ G（ d,p） level of theory. The results indicated that there are different binding sites in the molecules,and the binding energies of the clusters decreases due to the fluorine substituent. Atoms in molecules（ AIM） theory were applied to prove the existence of the hydrogen bonds in these clusters. The analysis of the geometries indicated that in the CH... X（ X = O,F） type clusters,the proton donor C-H bond in CHF_3 becomes shorter and the stretching vibrational frequency increases,but in the CH…π type clusters,no obvious rule exist for the changes of the bond length and the vibrational frequency. The natural bond orbital（ NBO） analysis was used to help investigate the formation of the hydrogen bond in some systems we studied,and the blue-shifted hydrogen bond may be explained by the dominant rehybridization effect.