TY  - JOUR
A1  - Noll, Niklas
A1  - Groß, Tobias
A1  - Shoyama, Kazutaka
A1  - Beuerle, Florian
A1  - Würthner, Frank
T1  - Folding‐Induced Promotion of Proton‐Coupled Electron Transfers via Proximal Base for Light‐Driven Water Oxidation
JF  - Angewandte Chemie International Edition
N2  - Proton‐coupled electron‐transfer (PCET) processes play a key role in biocatalytic energy conversion and storage, for example, photosynthesis or nitrogen fixation. Here, we report a series of bipyridine‐containing di‐ to tetranuclear Ru(bda) macrocycles 2 C–4 C (bda: 2,2′‐bipyridine‐6,6′‐dicarboxylate) to promote O−O bond formation. In photocatalytic water oxidation under neutral conditions, all complexes 2 C–4 C prevail in a folded conformation that support the water nucleophilic attack (WNA) pathway with remarkable turnover frequencies of up to 15.5 s\(^{−1}\) per Ru unit respectively. Single‐crystal X‐ray analysis revealed an increased tendency for intramolecular π‐π stacking and preorganization of the proximal bases close to the active centers for the larger macrocycles. H/D kinetic isotope effect studies and electrochemical data demonstrate the key role of the proximal bipyridines as proton acceptors in lowering the activation barrier for the crucial nucleophilic attack of H\(_{2}\)O in the WNA mechanism.
KW  - artificial photosynthesis
KW  - folded macrocyles
KW  - homogeneous catalysis
KW  - photocatalysis
KW  - Ruthenium complexes
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312020
VL  - 62
IS  - 7
ER  - 
TY  - JOUR
A1  - Würthner, Frank
A1  - Noll, Niklas
T1  - A Calix[4]arene‐Based Cyclic Dinuclear Ruthenium Complex for Light‐Driven Catalytic Water Oxidation
JF  - Chemistry - A European Journal
N2  - A cyclic dinuclear ruthenium(bda) (bda: 2,2’‐bipyridine‐6,6’‐dicarboxylate) complex equipped with oligo(ethylene glycol)‐functionalized axial calix[4]arene ligands has been synthesized for homogenous catalytic water oxidation. This novel Ru(bda) macrocycle showed significantly increased catalytic activity in chemical and photocatalytic water oxidation compared to the archetype mononuclear reference [Ru(bda)(pic)\(_2\)]. Kinetic investigations, including kinetic isotope effect studies, disclosed a unimolecular water nucleophilic attack mechanism of this novel dinuclear water oxidation catalyst (WOC) under the involvement of the second coordination sphere. Photocatalytic water oxidation with this cyclic dinuclear Ru complex using [Ru(bpy)\(_3\)]Cl\(_2\) as a standard photosensitizer revealed a turnover frequency of 15.5 s\(^{−1}\) and a turnover number of 460. This so far highest photocatalytic performance reported for a Ru(bda) complex underlines the potential of this water‐soluble WOC for artificial photosynthesis.
KW  - water
KW  - oxidation
KW  - ruthenium
KW  - dinuclear
KW  - catalytic
KW  - artificial photosynthesis
KW  - homogenous catalysis
KW  - photocatalysis
KW  - ruthenium complexes
KW  - water oxidation
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230030
UR  - https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202004486
VL  - 27
IS  - 1
ER  -