Enhanced Hydrogen Evolution in Neutral Water Catalyzed by a Cobalt Complex with a Softer Polypyridyl Ligand.
Angew Chem Int Ed Engl
; 59(31): 12694-12697, 2020 Jul 27.
Article
em En
| MEDLINE
| ID: mdl-32307871
ABSTRACT
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 -1.3â
V (vs. SHE) for 20â
hours with a turnover number (TON) of 266 300, and photolytic HER for two days with a TON of 15 000 in pHâ
7 aqueous solutions. The softer ligand scaffold possibly provides increased stability towards the intermediate CoI species. DFT calculations demonstrate that HER occurs through a general electron transfer/proton transfer/electron transfer/proton transfer pathway, with H2 released from the protonation of CoII -H species.
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MEDLINE
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En
Ano de publicação:
2020
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Article