title: Development of an efficient photocatalytic system for CO2 reduction using rhenium(I) complexes based on mechanistic studies.
abstract: The reaction mechanism of photocatalytic CO2 reduction using rhenium(I) complexes has been investigated by means of a detailed comparison of the photocatalyses of three rhenium(I) complexes, fac-[Re(bpy)(CO)3L] (L = SCN- (1-NCS), Cl- (1-Cl), and CN- (1-CN)). The corresponding one-electron-reduced species (OER) of the complexes play two important roles in the reaction: (a) capturing CO2 after loss of the monodentate ligand (L) and (b) donation of the second electron to CO2 by another OER without loss of L. In the case of 1-NCS, the corresponding OER has both of the capabilities in the photocatalytic reaction, resulting in more efficient CO formation (with a quantum yield of 0.30) than that of 1-Cl (quantum yield of 0.16), for which OER species have too short a lifetime to accumulate during the photocatalytic reaction. On the other hand, 1-CN showed no photocatalytic ability, because the corresponding OER species does not dissociate the CN- ligand. Based on this mechanistic information, the most efficient photocatalytic system was successfully developed using a mixed system with fac-[Re(bpy)(CO)3(CH3CN)]+ and fac-[Re{4,4'-(MeO)2bpy}(CO)3{P(OEt)3}]+, for which the optimized quantum yield for CO formation was 0.59.
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-E1-9 O-okayama, Meguro-ku, Tokyo, 152-8551, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takeda
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Koike
authors.forename: Haruo
authors.initials: H
authors.lastname: Inoue
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishitani
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D004563:Electrochemistry; D004583:Electrons; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D012211:Rhenium / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D002245:Carbon Dioxide; D012211:Rhenium