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

• Published in: Chemistry : a European journal Vol. 28; no. 24; pp. e202104562 - n/a
• Main Authors: Liu, Tianqi, Li, Ge, Shen, Nannan, Wang, Linqin, Timmer, Brian J. J., Kravchenko, Alexander, Zhou, Shengyang, Gao, Ying, Yang, Yi, Yang, Hao, Xu, Bo, Zhang, Biaobiao, Ahlquist, Mårten S. G., Sun, Licheng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 27.04.2022; John Wiley and Sons Inc
• Subjects: Acceleration; Catalysis; Catalysts; Catalytic activity; Chemical Sciences; Chemistry; Engineering Science with specialization in Nanotechnology and Functional Materials; Humans; Hydrophobicity; Intermediates; Kemi; Kinetics; Natural Sciences; Naturvetenskap; outer sphere; Oxidation; Oxidation-Reduction; proton transfer; Protons; Stabilization; Teknisk fysik med inriktning mot nanoteknologi och funktionella material; third coordination sphere; Water - chemistry; water oxidation; hydrophobicity; proton transfer; outer sphere; water oxidation; intermediates; third coordination sphere
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202104562

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. Outer coordination sphere engineering: A series of pocket‐shaped catalysts with well‐defined outer coordination environments were synthesized and characterized, showing that the hydrophobic outer coordination sphere could stabilize high‐valent intermediates and promote proton transfer during water oxidation catalysis. The introduction of hydrophobic outer‐sphere interactions is therefore envisaged as an effective strategy to tune other related proton‐coupled electron transfer (PCET) reactions.