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Enhanced Hydrogen Evolution in Neutral Water Catalyzed by a Cobalt Complex with a Softer Polypyridyl Ligand
Author(s) -
Wang Ping,
Liang Guangchao,
Smith Noah,
Hill Kyra,
Donnadieu Bruno,
Webster Charles Edwin,
Zhao Xuan
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202002640
Subject(s) - chemistry , protonation , catalysis , ligand (biochemistry) , cobalt , aqueous solution , electron transfer , pyridine , proton coupled electron transfer , amine gas treating , carboxylate , turnover number , medicinal chemistry , photochemistry , inorganic chemistry , stereochemistry , organic chemistry , ion , biochemistry , receptor
To explore the structure–function relationships of cobalt complexes in the catalytic hydrogen evolution reaction (HER), we studied the substitution of a tertiary amine with a softer pyridine group and the inclusion of a conjugated bpy unit in a Co complex with a new pentadentate ligand, 6‐[6‐(1,1‐di‐pyridin‐2‐yl‐ethyl)‐pyridin‐2‐ylmethyl]‐[2,2′]bipyridinyl (Py3Me‐Bpy). These modifications resulted in significantly improved stability and activity in both electro‐ and photocatalytic HER in neutral water. [Co(Py3Me‐Bpy)(OH 2 )](PF 6 ) 2 catalyzes the electrolytic HER at −1.3 V (vs. SHE) for 20 hours with a turnover number (TON) of 266 300, and photolytic HER for two days with a TON of 15 000 in pH 7 aqueous solutions. The softer ligand scaffold possibly provides increased stability towards the intermediate Co I species. DFT calculations demonstrate that HER occurs through a general electron transfer/proton transfer/electron transfer/proton transfer pathway, with H 2 released from the protonation of Co II −H species.