双氧/硫杂紫菜嗪内氢迁移反应的理论研究

Theoretical study on the inner hydrogen atom transfer reactions of di-oxa-or thia-porphyrin

本文在确定各反应体系反应物和产物稳定构象的基础上,采用B3LYP/6-31G^(**)方法利用Gaussian 03程序,对质子化的双氧/硫杂紫菜嗪的内氢迁移反应进行了研究,寻找并优化相应的过渡态,比较了其迁移反应速率的差异。计算结果表明,在中心空穴较小的体系中,空间位阻和静电作用对构象稳定性的影响显著增强,并有可能超越共轭效应而成为影响构象的首要因素。另外,在体系的总电子不变的前提下,缩小中心空穴,提高芳香性,有助于电荷的平均分布,可以明显减弱取代基对IHAT反应速率的影响。

With the stable conformations of all the reactants and products,the inner transfer reaction of hydrogen atoms in protonated di-oxa- or thia-porphyrin are studied in this worked.The B3LYP/6-31G^（＊＊） method is carried out using Gaussian 03 software.The transition states are found and optimized,and the speeds of different IHAT reactions are compared.The results show that,in the molecule system with smaller central holes,the steric hindrance and the electrostatic interaction have more impact on the relative stability of conformation.These two factors may even exceed the aromaticity and become the key elements for conformation.Besides,when the electron number is set invariable,decrease the size of the central hole can derive more uniform distribution of electric charges and also obviously reduce the effect of substitutions on IHAT reactive speeds.