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Unraveling the Light‐Activated Reaction Mechanism in a Catalytically Competent Key Intermediate of a Multifunctional Molecular Catalyst for Artificial Photosynthesis
Author(s) -
Zedler Linda,
Mengele Alexander Klaus,
Ziems Karl Michael,
Zhang Ying,
Wächtler Maria,
Gräfe Stefanie,
Pascher Torbjörn,
Rau Sven,
Kupfer Stephan,
Dietzek Benjamin
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201907247
Subject(s) - photochemistry , artificial photosynthesis , catalysis , chemistry , excited state , photocatalysis , resonance raman spectroscopy , reactive intermediate , raman spectroscopy , electrochemistry , electron transfer , electron paramagnetic resonance , reaction intermediate , redox , inorganic chemistry , organic chemistry , nuclear magnetic resonance , physics , electrode , nuclear physics , optics
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(PF 6 ) 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.