Electron Transfer Properties and Control of Active Oxygen Species

研究了各种超氧化物金属配合物的形成及其催化作用。超氧化物-金属离子配合物的电磁共振光谱的gzz值随金属离子类型的不同而有显著的变化。根据gzz值与自由自旋值的偏差，确定了π_g能级由于络合物的形成而产生的能量分裂值（ΔE）。ΔE值与金属离子在氧的电子转移还原反应中的催化活性有很好的相关性。超氧化物离子与金属离子之间的这种络合物的形成在超氧化物歧化酶的酶促功能、活性氧-铜络合物的形成以及O_2对锌卟啉-富勒烯连接分子的反向电子转移的新型催化作用中发挥了重要作用。以锰卟啉和树状大分子为催化剂也实现了包括水在内的底物的催化氧化，并通过对活性氧的检测和详细的动力学研究揭示了催化机理。利用二钴卟啉和适当的间隔剂，阐明了氧四电子还原成水的催化机理。

Formation of a variety of superoxide-metal complexes and the catalytic function have been investigated. The gzz-values of ESR spectra of superoxide-metal ion complexes vary significantly depending on the type of metal ions. From the deviation of the gzz-value from the free spin value are determined the energy splitting values (ΔE) of π_g levels due to the complex formation.The ΔE values are correlated well with the catalytic reactivities of metal ions in the electron transfer reduction of oxygen. Such a complex formation between superoxide ion and metal ions has been shown to play an essential role in the enzymatic function of superoxide dismutase, formation of active oxygen-opper complexes, and the novel catalytic effect of O_2 in back electron transfer of zinc porphyrin-fullerene linked molecules. The catalytic oxygenation of substrates including water has also been achieved using manganese porphyrins and dendrimers as catalysts and the catalytic mechanisms have been revealed based on the detection of active oxygen species and detailed kinetic studies. The catalytic mechanism of four-electron reduction of oxygen to water has also been elucidated using dicobalt porphyrins with an appropriate spacer.