卟吩异构体的结构和稳定性的理论研究

Theoretical study on the structures and stability of porphine isomers

本文用B3LYP/6-31G^(**)方法,计算了P^2-和PH^2的各种异构体,并对各种异构体的稳定性进行了比较和分析。结果显示:(1)Z构型比E构型稳定,且Z构型大多为平面或近平面结构,芳香性是决定π共轭体系稳定的决定性因素:(2)骨架相同的条件下,分子间氢键的数目较多,强度较大,以及中心空穴的空间位阻和静电斥力较小,是trans的PH_2异构体稳定性高于cis异构体的主要原因,但是这些影响因素并不能改变不同骨架的异构体的能量高低顺序.

In this paper, the structures of p2- and PH2 isomers are optimized, then the relative stabilities of isomers are discussed. The results show that： （1） Z- isomers are more stable than Eisomers, and they are mostly planar or nearly planar, so aromaticity is the main foctor to affect the relative stability of lr conjugated systems. （2） On condition of the same molecular skeleton, the trans configurations of PH2 isomers are more stable than cis configurations, which resulted from the numbers and intensities of hydrogen bonds, steric hindrance and the electrostatic repulsion. But these foctors won＇t change the relative energies of isomers with the different skeletons.