质子化双氧/硫杂卟啉内氢原子迁移反应的理论研究

Theoretical Study on the Inner Hydrogen Atom Transfer Reactions of Protonated Di-oxa- or Thia-porphyrin

在确定各反应体系反应物、产物稳定构象的基础上,采用B3LYP/6-31G**方法在Gaussian03程序下,对质子化的双氧/硫杂卟啉的内氢迁移(IHAT)反应进行研究,寻找并优化相应的过渡态,比较其迁移反应速率的差异.计算结果表明,质子化双氧/硫杂卟啉的构象稳定性仍然是由芳香性、空间位阻、静电作用共同决定的.质子化后的双取代体系的内氢迁移反应速率大小差异显著,内环取代对IHAT反应速率的影响主要来源于电子效应,而非构象变化;且双取代对体系IHAT反应速率的影响要远大于单取代.

On the basis of the stable structures of reactants and products, transfer reactions of inner hydrogen atoms in protonated di-oxa- or thia-porphyrin were studied. The transition states were found and optimized, and the differences between rates of inner hydrogen atom transfer （IHAT） reactions were presented. The calculated results show that the main foctors to affect the relative stability of conformations of the studied protonated molecular systems are aromaticity, the steric hindrance and the electrostatic interaction. The rate differences of IHAT reactions in these protonated double-substitution systems are remarkable. The IHAT reaction rate differences of inner ring substitution mainly resulted from electronic effects rather than conformational changes. In addition, the di-substitutional effects on the IHAT reaction rates are greatly larger than the mono-substitutional effects.