Faraggi M, Peretz P, Weinraub D
Int J Radiat Biol Relat Stud Phys Chem Med. 1986 Jun;49(6):951-68. doi: 10.1080/09553008514553181.
Solution properties of the iron-(III) 'picket-fence-like' porphyrin, Fe(III)-alpha,alpha,alpha, beta-tetra-ortho (N-methyl-isonicotinamidophenyl) porphyrin, (Fe(III)PFP) were investigated. These were acid/base properties of the aquo complex with pKa of 3.9 and its aggregation (formation of dimer with K = 1 X 10(-10) dm3 mol-1), complex formation with cyanide ions and 1-methyl imidazole (1-MeIm), spectral properties of the three iron complexes in their ferric and ferrous form and the one-electron reduction potential of these complexes. Knowing these properties, the reaction of the ferric complexes, aquo, dicyano and bis (1-MeIm), with the superoxide radical and other reducing radicals were studied using the pulse radiolysis technique. The second-order reaction rate constant of O2- with the iron (III) aquo complex which governs the catalytic efficiency of the metalloporphyrin upon the disproportionation of the superoxide radical was 7.6 X 10(7) dm3 mol-1 s-1, two orders of magnitude faster when compared to the reaction of each of the other complexes. The reduction by other radicals with all iron (III) complexes had similar second-order rate constants (10(9) to 10(10) dm3 mol-1 s-1). The reduction reaction in all cases produced Fe(II)PEP and no intermediate was found. The oxidation reaction of Fe(II)PEP by O2- was one order of magnitude faster when compared to the reduction of Fe(III)PFP by the same radical. Since the reactivity of O2- toward the three iron (III) porphyrin complexes follows their reduction potentials, it is suggesting the formation of a peroxo Fe(II) porphyrin as an intermediate. The reactions of the Fe(II)PFP complexes with dioxygen were also studied. The aquo complex was found to be first order in O2 and second order in Fe(II)PFP, suggesting the formation of a peroxo Fe(II) porphyrin as an intermediate. The intermediate formation was corroborated by evidence of the rapid CO binding reaction to the aquo complex of Fe(II)PFP. The two other complexes reacted very slowly with O2 as well as with CO.
研究了铁（III）“栅栏状”卟啉，即Fe（III）-α，α，α，β-四邻（N-甲基异烟酰胺基苯基）卟啉（Fe（III）PFP）的溶液性质。这些性质包括水合配合物的酸碱性质（pKa为3.9）及其聚集情况（形成二聚体，K = 1×10⁻¹⁰ dm³ mol⁻¹）、与氰离子和1-甲基咪唑（1-MeIm）形成配合物的情况、三种铁配合物在其铁离子和亚铁离子形式下的光谱性质以及这些配合物的单电子还原电位。了解这些性质后，使用脉冲辐解技术研究了铁离子配合物、水合配合物、二氰配合物和双（1-MeIm）配合物与超氧自由基及其他还原自由基的反应。超氧阴离子与铁（III）水合配合物的二级反应速率常数决定了金属卟啉对超氧自由基歧化反应的催化效率，为7.6×10⁷ dm³ mol⁻¹ s⁻¹），与其他每种配合物的反应相比快两个数量级。其他自由基与所有铁（III）配合物的还原反应具有相似的二级速率常数（10⁹至10¹⁰ dm³ mol⁻¹ s⁻¹）。在所有情况下，还原反应均生成Fe（II）PEP，未发现中间体。超氧阴离子对Fe（II）PEP的氧化反应比同一自由基对Fe（III）PFP的还原反应快一个数量级。由于超氧阴离子对三种铁（III）卟啉配合物的反应活性遵循它们的还原电位，这表明形成了过氧Fe（II）卟啉作为中间体。还研究了Fe（II）PFP配合物与氧气的反应。发现水合配合物对氧气为一级反应，对Fe（II）PFP为二级反应，这表明形成了过氧Fe（II）卟啉作为中间体。Fe（II）PFP水合配合物与一氧化碳的快速结合反应的证据证实了中间体的形成。另外两种配合物与氧气以及与一氧化碳的反应都非常缓慢。
