Research Interests/研究テーマ

Development of Environmentally Benign Bio-inspired Oxidation Catalysts 

Our research objective is to evaluate the chemical functions of metalloenzymes, biocatalysts involving transition-metal ion(s) in their active-sites, and apply them to catalytic oxidation reactions. Our targets are iron- and copper-containing oxygenases and molybdenum- and tungsten-containing oxidoreductases. The iron- and copper-containing metalloenzymes, for example, bind molecular oxygen in the air to transport it to all over our body and reductively activate it by injecting electrons and protons (eq. 1) to accomplish a series of oxidation/oxygenation reactions of a variety of substrates. Such reactions are indispensable to prepare useful materials and to degrade harmful compounds in our body. On the other hand, metalloenzymes involving a molybdenum or a tungsten ion activates water molecule by abstracting electrons and protons (eq 2) to perform oxygen atom transfer to several organic and inorganic substances. These reactions (eq 1 & 2) afford very clean and environmentally benign processes since they employ very cheap molecular oxygen or water molecule as the oxygen source and produce no harmful byproducts.  Thus, much recent attention has been focused on such ideal chemical processes.




In our laboratory, we are trying to evaluate the structures, physicochemical properties (spectroscopic, redox, and magnetic features), and reactivity of the active-oxygen species generated on the active-site transition-metal ion(s) and apply those strategies (eq 1 & 2) to develop efficient oxidation/oxygenation catalysts for practical applications. To accomplish these objectives, we employ several experimental techniques such as those of synthetic organic chemistry for the design and synthesis of new bio-inspired ligands, coordination chemistry for the synthesis of active-site model complexes, several spectroscopic techniques (UV-vis, IR, resonance Raman, fluorescence, X-ray crystallographic analysis, NMR, ESR, etc.) for structural and physicochemical evaluations, and electrochemistry and kinetics for mechanistic investigations. Furthermore, we are dealing with biochemistry of real proteins (enzymes), where not only mechanistic studies of the enzymes but also creation of novel artificial metalloenzymes are conducted by using advanced molecular biology techniques.


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