Heme is a key cofactor of hemoproteins in which porphyrin is often found to be preferen-tially metallated by an iron cation.Density functional reactivity theory ( DFRT ) descriptors and their spin-polarized version have been previously applied to understand the metal-binding specificity of porphy-rin in the literature.It was found that the iron-porphyrin complex significantly differs in many aspects from porphyrin complexes with other metal cations.In this study, we employ DFRT and its spin-polarized version to investigate the reactivity for a series of small ligands axially bonded to the iron-porphyrin com-plex with the general formula of L-Fe(Ⅱ)-porphyrin, where L=SMe, SHMe, 1H-imidazole, imidazol-1-ide, OH, H2 O, H2 O2 , CO, NO, O2 , furan, isoindole, pyrrole, and pyridine.Both global and local DFRT descriptors were examined within this framework.We found that, from the analysis of DFRT and spin-polarized DFRT descriptors, CO is the ligand giving rise to the most stable Fe(Ⅱ)-prophyrin com-plex, which at the same time is less reactive than other systems.We also discovered substantial differ-ences in structural and reactivity descriptors between the systems with L=H2 O and SHMe systems as well as the systems with L=OH and SMe.Quantitative reactivity relationships have been revealed.These re-sults should help better understanding of the reactivity of heme bonding with different ligands for heme-containing enzymes and other metalloproteins alike.%血红素在许多生化反应中起着至关重要的作用，且血红素的核心为卟啉环配位铁离子。文献采用密度泛函活性理论及其自旋极化方法对卟啉环连接的金属离子的选择性进行了研究，发现卟啉环连接铁离子时其结构和活性与连接其他金属离子的体系有很大的差异。实验研究表明，轴向连接不同配体对体系的结构和活性有显著影响。本文采用密度泛函活性理论及其自旋极化方法对铁卟啉体系中铁离子轴向连接不同配体的体系进行系统探究。轴向配体包括SMe， SHMe，1H-咪唑及衍生物， OH， H2 O， H2 O2， CO， NO， O2，呋喃，异吲哚，吡咯和吡啶。通过对全局和局域化学活性描述符的计算分析发现，当配体是CO时，体系化学性质稳定、反应活性也低；在众多种体系中H2 O和SHMe的得失质子对体系活性的影响最大。这些计算结果对更深入了解血红素及其类似体系的活性和作用机理有重要意义。
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