Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Liu, Tianqi; Li, Ge; Shen, Nannan; Wang, Linqin; Timmer, Brian J. J.; Zhou, Shengyang; Zhang, Biaobiao; Кравченко, А. И.; Bai, Xu; Ahlquist, Mårten S. G.; Sun, Licheng

doi:10.31635/ccschem.021.202101159

Cited by 19 publications

(25 citation statements)

References 50 publications

(38 reference statements)

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“…Catalysts with a hydrophobic outer sphere outperformed their hydrophilic analogs (Figure 4 and Table 1), indicating the promotional effects of hydrophobic outer spheres. Especially, and c) [20]…”

Section: Resultsmentioning

confidence: 99%

“…Complex 1 has been previously reported to capture the seven-coordinate aqua ligand at a low oxidation state. [20] The other three pocketshape catalysts 2-4 and structural Ref. [5] [21] were synthesized following similar procedures (cf.…”

Section: Resultsmentioning

confidence: 99%

“…[5] could rotate freely (flexible conformation), while the small hydrophilic pocket ligand of complex 1 is limited to left-to-right switching in front of the catalytic site (locked conformation). [20] In the locked conformation, protons H g and H d are differently affected by the ring current of the bda-ligand, leading to the downfield shift for H d and upfield shift for H g (Figure 2). Complex 2 and 4 with the hydrophobic pocket ligands exhibited similar tendencies in chemical shifts, therefore the locked conformations could be envisaged.…”

Section: Resultsmentioning

confidence: 99%

“…In this study, four pocket‐shaped water oxidation catalysts (Figure 1) were designed as models of interest in which the hydrophilic/hydrophobic microenvironments provided by the distal ligands could be fine‐tuned [20] . The effect of the outer sphere on the structure‐activity relationship was clarified to provide a better understanding of the modus operandi of water oxidation, i. e., the hydrophobic microenvironment facilitates proton transfer and stabilizes high‐valent intermediates in water oxidation catalysis.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 3. Single crystal structures of complex 1 • H 2 O (a and c)[20] and 3 • H 2 O (b and d) with thermal ellipsoids at 50 % probability. Hydrogen atoms are omitted for clarity.…”

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confidence: 99%

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Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions

Liu

Shen

et al. 2022

Chemistry A European J

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The outer coordination sphere of metalloenzyme often plays an important role in its high catalytic activity, however, this principle is rarely considered in the design of man‐made molecular catalysts. Herein, four Ru‐bda (bda=2,2′‐bipyridine‐6,6′‐dicarboxylate) based molecular water oxidation catalysts with well‐defined outer spheres are designed and synthesized. Experimental and theoretical studies showed that the hydrophobic environment around the Ru center could lead to thermodynamic stabilization of the high‐valent intermediates and kinetic acceleration of the proton transfer process during catalytic water oxidation. By this outer sphere stabilization, a 6‐fold rate increase for water oxidation catalysis has been achieved.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Figure 3. Single crystal structures of complex 1 • H 2 O (a and c)[20] and 3 • H 2 O (b and d) with thermal ellipsoids at 50 % probability. Hydrogen atoms are omitted for clarity.…”

mentioning

confidence: 99%

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Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions

Liu

Shen

et al. 2022

Chemistry A European J

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Folding‐Induced Promotion of Proton‐Coupled Electron Transfers via Proximal Base for Light‐Driven Water Oxidation

et al. 2023

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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 bipyridinecontaining di-to tetranuclear Ru(bda) macrocycles 2 C-4 C (bda: 2,2'-bipyridine-6,6'-dicarboxylate) to promote OÀ 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 À 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.

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Pivotal Role of Geometry Regulation on O−O Bond Formation Mechanism of Bimetallic Water Oxidation Catalysts

Chen,

Xian,

Zhang

et al. 2024

Angewandte Chemie

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In this study, we highlight the impact of catalyst geometry on the formation of O−O bonds in Cu2 and Fe2 catalysts. A series of Cu2 complexes with diverse linkers were designed as electrocatalysts for water oxidation. Interestingly, the catalytic performance of these Cu2 complexes is enhanced as their molecular skeleton become more rigid, which contrast with the behavior observed in our previous investigation with Fe2 analogs. Moreover, mechanistic studies reveal that the reactivity of the bridging O atom results in distinct pathways for O−O bond formation in Cu2 and Fe2 catalysts. In Cu2 systems, the coupling takes place between a terminal CuIII−OH and a bridging μ−O• radical. Whereas in Fe2 systems, it involves the coupling of two terminal Fe−oxo entities. Furthermore, an in‐depth structure‐activity analysis uncovers the spatial geometric prerequisites for the coupling of the terminal OH with the bridging μ−O• radical, ultimately leading to the O−O bond formation. Overall, this study emphasizes the critical role of precisely adjusting the spatial geometry of catalysts to align with the O−O bonding pathway.

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Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Cited by 19 publications

References 50 publications

Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions

Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions

Folding‐Induced Promotion of Proton‐Coupled Electron Transfers via Proximal Base for Light‐Driven Water Oxidation

Pivotal Role of Geometry Regulation on O−O Bond Formation Mechanism of Bimetallic Water Oxidation Catalysts

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