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)2RuII(tpphz)RhICp*] of [(tbbpy)2Ru(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.

No abstract

No abstract

A new dyad consisting of a Ru(II) chromophore, a tetrapyridophenazine bridging ligand and a Rh(Cp*)Cl catalytic center, [Ru(tbbpy)2(tpphz)Rh(Cp*)Cl]Cl(PF6)2, acts as durable photocatalyst for hydrogen production from water. Catalytic activity is observed for more than 650 hours. Electrochemical investigations reveal that up to two electrons can be transferred to the catalytic center by a thermodynamically favorable intramolecular process, which has so far not been reported for similar tpphz based supramolecular photocatalysts. Additionally, mercury poisoning tests indicate that the new dyad works as a homogeneous photocatalyst.

A hetero‐binuclear dyad that contains a ruthenium polypyridyl moiety bound through an aromatic bridging ligand to an organometallic catalytic center has been used for the light‐driven reduction of the N‐benzyl‐3‐carbamoylpyridinium cation, NAD+, and NADP+ to yield the two‐electron‐reduced analog. Direct coupling with enzymatic conversion was proved by using UV/Vis spectroscopy and liquid chromatography, which showed cofactor‐recycling and enzymatic conversion with a turnover number of 350 per photocatalyst. First insights into the complex behavior of the catalytic system under irradiation point towards multiple prerequisites on the molecular as well as on the macroscopic level to generate highly efficient semiartificial photo‐biocatalytic systems for future energy‐storage applications.