Mechanistic analysis of metal-oxygen active species and their synthetic application to new catalytic oxidation

本研究旨在阐明血红素酶的人工模型复合物的双氧活化过程，通过光谱表征的活性中间体，如过氧和氢过氧血红素物种，这是由相应的双氧加合物的γ-射线低温辐射分解（单电子还原）产生的。所采用的配合物具有模拟物的基本功能团，a）轴向配体，B）氢键朝向双氧，发现在血红素酶的活性位点。从氧复合物的2K-低温辐射分解得到的物种被分配到低自旋六配位过氧铁血红素。在133 K退火后，形成氢过氧物种。这些结果证实，本发明的配合物可以重现的第一个重要部分的双氧活化过程组成的协调的双氧的还原和质子化的产生的peroxo group. Fe卟啉配合物，其中带有四个或两个萘酚羟基的金属中心附近，合成前列腺素H合酶的模型。在该酶的催化循环中，酪氨酰残基被氧化为苯氧自由基，从而夺取聚烯烃底物的特定氢原子。本模型配合物被过氧酸氧化，得到由萘氧基自由基和铁离子组成的活性物种，如在酶中观察到的。活性物种可以将非共轭二烯底物氧化成相应的氢过氧化物，同时回收起始的附加有萘酚的铁络合物。通过X-射线晶体学确定了其中一个模型配合物的结构。

This study is intended to clarify the dioxygen activation process by artificial model complexes for heme enzymes through the spectroscopic characterization of the reactive intermediates such as peroxo-and hydroperoxo heme species, which are generated by the cryoradiolysis with γ-ray (one-electron reduction) of the corresponding dioxygen adducts. The employed complexes have the mimics of the essential functional groups, a) axial ligand, b) hydrogen bondings toward dioxygen, found in the active sites of heme enzymes. The resulting species from the 2K-cryoradiolysis of oxy-complex was assignable to a low-spin six-coordinated peroxoferric heme. After annealing at 133K, a hydroperoxo species was formed. These results confirm that the present complex can reproduce the first important part of the dioxygen activation process composed of the reduction of the coordinated dioxygen and the protonation of the resulting peroxo group.Iron porphyrin complexes, which bear four or two naphtholic hydroxyl groups in the vicinity of the metal center, were synthesized as models of prostaglandin H synthase. In the catalytic cycle of this enzyme, the tyrosyl residue is oxidized to the phenoxyl radical, which abstracts the specific hydrogen atom of the polyolefinic substrate. The present model complexes were oxidized with peroxy acid to give the active species composed of naphthoxyl radical and ferryl ion, as observed in the enzyme. The active species can oxidize non-conjugated diene substrate to the corresponding hydroperoxide with the recovery of the starting naphthol-appended ferric complex. The structure of one of the model complexes was determined by X-ray crystallography.