取代基和配体的负离子效应对(TPFC)Mn(Ⅴ)O轴向配位作用的影响

Effects of Substituents and Anionic Ligands on Axial Coordination of(TPFC) Mn(Ⅴ)O

采用密度泛函理论(DFT)的BP86方法对系列β位取代的锰(Ⅴ)-氧咔咯(TPFC) Mn(Ⅴ) O配合物与咪唑的轴向配位作用,以及无β位取代的(TPFC) Mn(Ⅴ) O与4-甲基咪唑和吡咯的轴向配位性质进行理论研究.计算结果显示:β位取代基吸电子性质和轴向配体负离子效应均能缩短配位键长并增强结合能,显著增强(TPFC) Mn(Ⅴ) O配合物的轴向配位作用,其中轴向配体负离子效应影响更加显著.通过自然键轨道(NBO)分析发现,这2种效应加强(TPFC) Mn(Ⅴ) O轴向配位作用的主要因素:配位氮原子的孤对电子轨道LP(N)与Mn原子的孤对电子轨道LP(Mn,4s)和锰氧反键轨道σ*(Mn≡O)间形成较大的二级微扰稳定化能E(2).

The axial coordination of a series of β site substituted manganese(Ⅴ)-oxygen corrole( TPFC) Mn(Ⅴ) O with imidazole and the non β site substituted( TPFC) Mn(Ⅴ) O with 4-methyl imidazole and pyrrole were investigated using the BP86 method of the density functional theory( DFT). The calculation results show that the electronwithdrawing ability of the β-substituents and the anionic effect of the axial ligand can both result in a short length of coordination bond and the strong binding energy which significantly enhances the axial coordination interaction of the( TPFC) Mn(Ⅴ) O,especially the anionic effect of the axial ligand. As the natural bond orbital( NBO) analysis shows,the main factor for both effects on the axial coordination of( TPFC) Mn(Ⅴ) O is the strong second-order perturbation stabilization energy E( 2) that is formed between the lone-pair electron orbit of nitrogen on the axial ligand LP( N) and the lone-pair electron orbital of manganese LP( Mn,4 S) and the antibond orbital of manganese oxygen bond σ*( Mn≡O).