Unraveling the Light‐Activated Reaction Mechanism in a Catalytically Competent Key Intermediate of a Multifunctional Molecular Catalyst for Artificial Photosynthesis. Issue 37 (19th August 2019)

• Record Type: Journal Article
• Authors: Zedler, Linda; Mengele, Alexander Klaus; Ziems, Karl Michael; Zhang, Ying; Wächtler, Maria; Gräfe, Stefanie; Pascher, Torbjörn; Rau, Sven; Kupfer, Stephan; Dietzek, Benjamin
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 37(2019)
• Page Start: 13140
• Page End: 13148
• Publication Date: 2019-08-19
• Subjects: enzyme catalysis -- rhodium -- ruthenium -- spectro-electrochemistry -- ultrafast spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201907247
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Understanding photodriven multielectron reaction pathways requires the identification and spectroscopic characterization of intermediates and their excited‐state dynamics, which is very challenging due to their short lifetimes. To the best of our knowledge, this manuscript reports for the first time on in situ spectroelectrochemistry as an alternative approach to study the excited‐state properties of reactive intermediates of photocatalytic cycles. UV/Vis, resonance‐Raman, and transient‐absorption spectroscopy have been employed to characterize the catalytically competent intermediate [(tbbpy)2 Ru II (tpphz)Rh I Cp*] of [(tbbpy)2 Ru(tpphz)Rh(Cp*)Cl]Cl(PF6 )2 (Ru(tpphz)RhCp* ), a photocatalyst for the hydrogenation of nicotinamide (NAD‐analogue) and proton reduction, generated by electrochemical and chemical reduction. Electronic transitions shifting electron density from the activated catalytic center to the bridging tpphz ligand significantly reduce the catalytic activity upon visible‐light irradiation. Abstract : The working gears of a photocatalyst : Using spectroelectrochemistry with UV/Vis, resonance‐Raman, and transient‐absorption spectroscopy, the reactive intermediates of the photocatalytic cycle of the photocatalyst [(tbbpy)2 Ru(tpphz)Rh(Cp*)Cl]Cl(PF6 )2 have been studied in detail. Photo‐induced electronic transitions limiting the catalytic efficiency have been identified and can guide structural improvements.