Understanding the structures and aromaticity of heteroporphyrins with computations
Understanding the structures and aromaticity of heteroporphyrins with computations
复制标题
通过计算了解杂卟啉的结构和芳香性
DOI：
10.1039/d0ob00656d
复制
发表时间：
2020
影响因子：
3.2
通讯作者：
Yuan-Bin She
中科院分区：
文献类型：
--
作者：
Xiao-Li Fang;Xia-He Chen;Qun-Min Wang;Yun-Fang Yang;Yuan-Bin She
杂卟啉是一种卟啉衍生物，由其他含杂原子基团如PH、AsH、SiH2、O、S等取代吡啶NH部分。对于所有研究的异卟啉，由于大杂原子的存在，大环结构被扭曲。与常规卟啉相比，异卟啉的HOMO-LUMO间隙通常减小。计算了与原子核无关的化学位移值和感应电流密度的可视化各向异性来描述异卟啉的芳构性。感应电流密度的各向异性图表明，环电流在每个环上分为外通路和内通路。电流主要在有内氢的吡啶环上通过外通路，在没有内氢的吡啶环上通过内通路。在正规卟啉和o -取代杂卟啉中，芳香途径主要由22π电子芳香途径模型贡献。PH、AsH、S、Se、Te等杂原子对杂卟啉的芳构性影响不大。此外，CH2和SiH2部分的π共轭也被中断，环电流主要通过CH2和SiH2取代吡咯NH部分的杂卟啉外通路。因此，18π-[18]环烯模式在PH-、AsH-、S-、Se-、Te-、CH2-和sih2取代的杂卟啉中占主导地位。这些计算研究为进一步研究杂卟啉的芳香特性提供了新的思路，为进一步开发各种新型杂卟啉提供了依据。
Heteroporphyrins are porphyrin derivatives with replacement of the pyrrolic NH moiety by other heteroatom-containing groups, such as PH, AsH, SiH2, O, S, etc. For all studied heteroporphyrins, the macrocycle structure is distorted due to the presence of large heteroatoms. The HOMO–LUMO gap of heteroporphyrins is generally decreased compared to regular porphyrins. Both nucleus independent chemical shifts values and visualized anisotropy of induced current density were computed to describe the aromaticity of heteroporphyrins. The plots of anisotropy of induced current density suggest that the ring current diverged into an outer and an inner pathway at each ring. The current mainly passes through the outer path at the pyrrolic rings with inner hydrogen and through the inner path at the pyrrolic rings without inner hydrogen. In both regular porphyrin and O-substituted heteroporphyrins, the aromatic pathway is mainly contributed by the 22π-electron aromatic route model. Heteroatoms such as PH, AsH, S, Se and Te have little contribution to the aromaticity of heteroporphyrins. In addition, the π conjugation is also interrupted at the CH2 and SiH2 moiety, and the ring current mainly passes through the outer path of the heteroporphyrins with CH2 and SiH2 replacing the pyrrolic NH moiety. Therefore the 18π-[18]annulene model is dominated in PH-, AsH-, S-, Se-, Te-, CH2- and SiH2-substituted heteroporphyrins. These computational studies shed new light on the aromatic characters of heteroporphyrins, and will facilitate the further development of various novel heteroporphyrins.