铁卟啉化合物与氧气分子形成的体系的密度泛函理论研究(英文)

Density functional theory(DFT) studies of iron porphyrin complex-oxygen molecule systems

采用密度泛函理论B3LYP方法在6-31G（d）基组水平下对氯化铁（＋3）卟啉与氧气分子形成的体系进行了研究，得到了几何构型，电子性质及分子轨道结构等相关数据．对两个体系不同自旋状态下的几何构型参数和电子性质对比发现：受体系立体构型对称性的影响，在两个体系中凡是与卟啉环上N原子相关的几何参数及电子性质均呈现出相同规律性．又采用密度泛函理论UB3LYP／6—311G^＊／／UB3LYP／6．31G^＊方法对这两个体系不同自旋状态下的能量进行了计算，分析表明自旋多重度越高体系越稳定．然后分别分析了两个体系在最稳定自旋状态下的分子轨道占据情况及中心Fe原子最外层3d轨道的电子分布情况，结果表明Fe原子的3dz2和3dxz／3dyz与氧气分子的单占据反键轨道HOMOπ^＊2px/π^＊2py之间存在相互作用，这种相互作用引起铁卟啉环与O2分子间的电子转移并使O2活化．然而，根据分析在通常状态下铁卟啉对O2分子的活化作用是微弱的．

The geometry optimizations and the molecular orhitals of the iron（I/I） porphyrin chloride-oxygen molecule system [FePCl-O2] and the iron（W） tetraphenylporphyrin chloride-oxygen molecule system [Fe（TPP）C1-O2] are carried out by using the density functional theory（DFT） UB3LYP method with the 6-31G^＊ basis set. The geometry parameters and the electron properties for the two systems in different spin states are compared. The results show the parameters and electron properties correlated with the N atoms on porphyrin ring display some rule due to the systems＇ symmetrical structures. And the energies of the systems in different spin states are calculated by using UB3LYP/6-311G^＊//UB3LYP/6-31G^＊ method. The results reveal the stability of the two systems in different spin states decreases along the series octet〉sextet〉quartet. The molecular orbitals of the two systems in the most stable spin state are analyzed in detail. The results show it is the 3dz2 and 3dxz/3dyz atomic orbitals of the Fe atom that interact with the single occupied HOMO π^＊2px/π^＊2py of the O2 molecule feebly, which cause the electrons transfer and activate the O2 molecule. The activation of O2 molecule is weak in theory.