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Photochemical and Electrochemical Reduction of Carbon Dioxide to Carbon Monoxide Mediated by (2,2′‐Bipyridine)tricarbonylchlororhenium(I) and Related Complexes as Homogeneous Catalysts
Author(s) -
Hawecker Jeannot,
Lehn JeanMarie,
Ziessel Raymond
Publication year - 1986
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19860690824
Subject(s) - chemistry , rhenium , formate , photochemistry , carbon monoxide , bipyridine , catalysis , electron transfer , electrochemistry , quantum yield , amine gas treating , ligand (biochemistry) , electrochemical reduction of carbon dioxide , reaction rate constant , inorganic chemistry , organic chemistry , kinetics , biochemistry , physics , receptor , electrode , quantum mechanics , crystal structure , fluorescence
[ fac ‐Re(bpy) (CO) 3 Cl] (bpy = 2,2′‐bipyridine) is an efficient homogeneous catalyst for the selective and sustained photochemical or electrochemical reduction of CO 2 to CO. A quantum yield of 14% and a faradic efficiency of 98% were measured in the presence of excess Cl − ions. The photochemical process took place under visible‐light irradiation and consumed a tertiary amine as electron donor. A formato‐rhenium complex was isolated in the absence of excess Cl − ions. Substitution by Cl − ion generated free formate, but no CO was detected. Luminescence measurements showed that the tertiary amine quenches the metal‐to‐ligand charge‐transfer excited state of the rhenium complex via a reductive mechanism, with a rate constant of 3.4 × 10 7 M −1 S −1 . The 19e‐complex [Re(bpy) (CO) 3 X] − produced either photochemically or electrochemically appears to be the active precursor in the CO‐generation process. Detailed spectroscopic studies on 13 C‐enriched carbonyl‐rhenium and formato‐rhenium complexes derived from 13 C‐enriched CO 2 were performed in order to confirm the origin of the products and to study the exchange of the ligands. A mechanism for the present CO 2 photoreduction process is presented; it involves separate pathways for CO and formate generation, in which the [Re(bpy) (CO) 3 X] complex plays the role of both the photoactive and the catalytic center .