Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 59, Issue 31, Pages 12694-12697Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.202002640
Keywords
cobalt complexes; density functional calculations; hydrogen evolution; ligand design
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Funding
- National Science Foundation [CAREER CHE-1352036, CHE-1800201, OIA-1539035, CHE-1531466]
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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)(OH2)](PF6)(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.
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