Artificial photosynthesis via two-electron conversion: Photochemical oxygenation sensitized by ruthenium porphyrins with water as both electron and oxygen atom donor*
Haruo Inoue, Shigeaki Funyu, Yutaka Shimada, and Shinsuke Takagi
Department of Applied Chemistry, Graduate Course of Engineering, Tokyo Metropolitan University, Japan Science and Technology, Minami-ohsawa, Hachiohji, Tokyo 192-0397, Japan
Abstract: Recent progress in the field of artificial photosynthesis is reviewed. Among various approaches to oxidizing the water molecule, attention has been focused on the two-electron chemical conversion processes mediated by metallo-porphyrins upon visible light irradiation. Photochemical oxygenation reactions such as the epoxidation of alkenes sensitized by ruthenium(II) porphyrins with water as both electron and oxygen atom donor have been found. Ru porphyrin induces highly efficient two-electron oxidation of water with a quantum yield of 60 % to form an epoxide from the alkene with high selectivity. The water molecule serves as both an efficient electron and oxygen atom donor in the reaction, in which the oxygen atom of water is incorporated in a useful product, i.e., epoxide.
Keywords: artificial photosynthesis; oxidation of water; epoxidation; ruthenium porphyrin; photochemical oxygenation; photochemistry; oxygenation.
*Paper based on a presentation at the XXth IUPAC Symposium on Photochemistry, Granada, Spain, 17-22 July 2004. Other presentations are published in this issue, pp. 925-1085.