金属卟啉与咪唑及吡啶轴向配位作用的密度泛函理论研究

A density functional theory study for the coordination of metalloporphyrins with imidazole and pyridine

为了考察金属卟啉与含氮杂环化合物之间的轴向配位作用,本文采用密度泛函理论方法研究了中心金属分别为铁、锰、钴的3种金属卟啉与咪唑及吡啶2种轴向配体之间形成的配位络合物,从几何结构、相互作用能方面考察了配位络合物的稳定性、并从电荷和前线分子轨道能级方面解释了所形成配位络合物稳定性的差异。计算结果表明,具有不同中心金属离子的卟啉与不同轴向配体之间的配位作用也不同,卟啉中心金属的正电性越强,其与咪唑及吡啶所形成的配位络合物越稳定。3种金属卟啉中,铁卟啉中心金属具有较多的正电荷,更易与咪唑或吡啶发生轴向配位作用形成稳定的配位络合物。与吡啶相比,咪唑与金属卟啉之间的配位作用更强,形成的配位络合物更稳定。

In order to investigate the axial coordination between metalloporphyrins and nitrogen containing heterocyclic compounds, the complexes formed by three metalloporphyrins and two axial ligands （imidazole and pyridine） were studied by density functional theory. The stability of different complexes was investigated by analyzing the complex structures, the interaction energy, Mulliken charge and frontier molecular orbital energy levels of metalloporphyrins and axial ligands. The calculation results show that the coordination strength is different for different metalloporphyrins and axial ligands. The complexes are more stable for the metalloporphyrins with stronger electropositive central metal. Among the three metalloporphyrins, iron pophyrin with more positive charge in the central metal is more easily to form stable coordination complexes with imidazole or pyridine. Compared with pyridine, the coordination between metalloporphyfins and imidazole is stronger, and the complexes are more stable.