Oxidizing intermediates from the sterically hindered iron salen complexes related to the oxygen activation by nonheme iron enzymes
Oxidizing intermediates from the sterically hindered iron salen complexes related to the oxygen activation by nonheme iron enzymes
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DOI：
10.1021/ic051377e
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发表时间：
2005-10-31
影响因子：
4.6
通讯作者：
Fujii, H
中科院分区：
文献类型：
--
作者：
Kurahashi, T;Kobayashi, Y;Fujii, H
氧化中间体产生nonheme铁（III）配合物，调查的电子结构和反应性，在比较与氧代铁（IV）卟啉π-阳离子自由基（化合物1）作为血红素酶模型。带有第五配体Cl（1）、OH 2（2）、OEt（3）和OH（4）的位阻铁salen络合物被电化学和化学氧化。1和2的逐步单电子氧化产生铁（III）单-和二苯氧基自由基，如通过详细的光谱研究所揭示的，包括UV-vis、EPR、穆斯堡尔、共振拉曼和ESIMS光谱。与在单电子氧化时由羟铁（III）卟啉形成氧代铁（IV）相反，羟络合物4不产生氧代铁（IV）物质。2与mCPBA的反应也导致铁（III）-苯氧基自由基的形成。3的单电子氧化导致第五个DO配体的氧化降解，甚至在203 K下释放乙醛。铁（III）苯氧基自由基对铁（III）上的醇氧化物显示出高反应性，但对醇（甚至包括苄醇）几乎没有反应性，而没有碱来除去醇质子。这项研究解释了独特的性质的单核nonheme酶与Tyr残基，也差的环氧化活性的Fe salen相比，锰和铬salen化合物。
Oxidizing intermediates are generated from nonheme iron(III) complexes to investigate the electronic structure and the reactivity, in comparison with the oxoiron(IV) porphyrin pi-cation radical (compound 1) as a heme enzyme model. Sterically hindered iron salen complexes, bearing a fifth ligand Cl (1), OH2 (2), OEt (3), and OH (4), are oxidized both electrochemically and chemically. Stepwise one-electron oxidation of 1 and 2 generates iron(Ill)mono- and diphenoxyl radicals, as revealed by detailed spectroscopic investigations, including UV-vis, EPR, Mossbauer, resonance Raman, and ESIMS spectroscopies. In contrast to the oxoiron(IV) formation from the hydroxoiron(III) porphyrin upon one-electron oxidation, the hydroxo complex 4 does not generate oxoiron(IV) species. Reaction of 2 with mCPBA also results in the formation of the iron(Ill)-phenoxyl radical. One-electron oxidation of 3 leads to oxidative degradation of the fifth DO ligand to liberate acetaldehyde even at 203 K. The iron(Ill)phenoxyl radical shows high reactivity for alcoxide on iron(III) but exhibits virtually no reactivity for alcohols including even benzyl alcohol without a base to remove an alcohol proton. This study explains unique properties of mononuclear nonheme enzymes with Tyr residues and also the poor epoxidation activity of Fe salen compared to Mn and Cr salen compounds.