Axial ligands control the various chemical reactions triggered by heme proteins. Thus, studies on the reaction of iron porphyrin with ligands are important for understanding their functions. Here, a spectroscopic investigation was performed to clarify the distortion effect of the porphyrin ring on the ligation of imidazoles (imidazole (Im), 1-methyl- and 2-methylimidazole (1-MeIm and 2-MeIm)) to iron(III) porphyrin. The overall stability constant (${\beta }_2)$ was found to have increased, while $K_1$ decreased with increasing distortion of the porphyrin core. However, the ${\beta }_2$ of the tetraphenyl-substituted complex, which is considered the least distorted, was not minimal, while the $K_1$ was not maximal. These results suggest that the stability of bis-ligand iron(III) porphyrin complexes depends on the increase in the saddle-type distortion of the porphyrin, the type of distortion, and the steric hindrance at the surrounding substituents. Furthermore, the ligation of 1-MeIm to iron(III) porphyrin hydroxo complexes with the porphyrin ring distortion was investigated. The ligation of 1-MeIm to the iron(III) dodecaphenylporphyrin hydroxo complex (DPPFeOH) suggests that a reaction mechanism different from the general reaction mechanism may occur simultaneously, i.e., a simultaneous reaction. In addition, the ${\beta }_2$ of DPPFeOH was found to be approximately 15 times smaller than that of the chloride complex. The relationship between the distortion and stability of bis-ligands iron(III) porphyrin complexes obtained in this study is expected to assist in the elucidation of the model reaction of heme proteins.

轴向配体控制血红素蛋白引发的各种化学反应。因此，研究铁卟啉与配体的反应对于理解其功能非常重要。在这里，进行了光谱研究，以澄清卟啉环对咪唑（咪唑（Im）、1-甲基-和2-甲基咪唑（1-MeIm 和 2-MeIm））与铁（III）连接的畸变影响卟啉。整体稳定常数（${\beta }_2）$发现增加了，同时$K_1$随着卟啉核心变形的增加而减少。但是，那${\beta }_2$四苯基取代的络合物被认为是扭曲程度最小的，但其值也不是最小的，而$K_1$不是最大的。这些结果表明，双配体铁(III)卟啉配合物的稳定性取决于卟啉鞍型畸变的增加、畸变的类型以及周围取代基的空间位阻。此外，还研究了1-MeIm与铁(III)卟啉羟基配合物与卟啉环扭曲的连接。1-MeIm与铁(III)十二苯基卟啉羟基络合物( DPPFeOH )的连接表明不同于一般反应机制的反应机制可能同时发生，即同时反应。除此之外${\beta }_2$发现DPPFeOH的尺寸大约比氯化物配合物的尺寸小 15 倍。本研究中获得的双配体铁(III)卟啉复合物的畸变与稳定性之间的关系有望有助于阐明血红素蛋白的模型反应。