卟吩内氢迁移反应机理的密度泛函研究

将密度泛函理论应用于卟吩内氢迁移反应机理的理论研究,计算反式卟吩trans-PH2和顺式卟吩cis-PH2的结构参数、总能量、电子密度和振动频率等参数。计算发现trans-PH2比cis-PH2的能量低29．13 kJ／mol(接近实验数据25．0 kJ／mol)。振动分析表明中间态TS-PH2只有一个虚频,而中间态SS-PH2有两个虚频,可以判定TS-PH2是分步反应机理的过渡态,而且同步反应历程比分步反应历程需要更大的活化能,因此可得出卟吩内氢迁移反应采用分步反应历程的结论。此研究表明,密度泛函理论的计算结果与实验数据能够较好地相吻合,能直观地表述卟吩内氢迁移反应的机理,从理论上解释了该反应采用分步反应机理。

DFT study in inner hydrogen atoms transfer mechanism of porphine

The transfer reaction of inner hydrogen atoms in porphine is calculated by using density functional theory. The structural parameters, total energies, electron density, vibration frequencies, deformation density and Fukui indices were calculated. The calculation results showed that the difference of energies between trans-PH2 and cis-PH2 was 29. 13 kJ/mol, the value was more close to the experimental data than those in the references. TS-PH2 possessed only one imaginary frequency, while SS-PH2 possessed two imaginary frequencies. This showed that TS-PH2 was the transition state of asynchronous mechanism. The activation energy of asynchronous mechanism was smaller than the activation energy of synchronous mechanism. So the tautomerization adopts asynchronous mechanism. So the application of DFT in the transfer reaction of inner hydrogen atoms in porphine was successful.