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Polar Substituents Enable Efficient Catalysis for a Class of Cobalt Polypyridyl Hydrogen Evolving Catalysts


Müller, Peter; Probst, Benjamin; Spingler, Bernhard; Blacque, Olivier; Alberto, Roger (2022). Polar Substituents Enable Efficient Catalysis for a Class of Cobalt Polypyridyl Hydrogen Evolving Catalysts. Helvetica Chimica Acta, 105(3):e202100237.

Abstract

A series of structurally related, acyclic cobalt tetrapyridyl hydrogen evolving catalysts (HEC) were prepared and characterized. The common motif, di(2,2′-bipyridin-6-yl)-methane, was derivatized at the bridging methylene to include a carbonyl group (L1), a hydroxy (L2), a methyl and a hydroxy (L3), a 1,1′-biphenyl-2,2′-diyl (L4), a hydroxy and a phenyl (L5) or a hydroxy and a pyrid-6-yl group. These catalysts were compared with the known HEC [Co(appy)Br]Br. Photo- and electrochemistry showed a distinct influence of the bridging position on rates and stabilities of the hydrogen evolution reaction (HER). Apolar ligands resulted in inferior catalytic performance as compared to HECs with polar substituents. Electrochemically, [Co(L1)Br2] was shown to be converted to [Co(L2)Br2] in catalysis. The best catalyst made more than 10’000 turnovers, albeit at an overpotential of 600 mV. Additional pH dependent mechanistic aspects were elucidated by cyclic voltammetry.

Abstract

A series of structurally related, acyclic cobalt tetrapyridyl hydrogen evolving catalysts (HEC) were prepared and characterized. The common motif, di(2,2′-bipyridin-6-yl)-methane, was derivatized at the bridging methylene to include a carbonyl group (L1), a hydroxy (L2), a methyl and a hydroxy (L3), a 1,1′-biphenyl-2,2′-diyl (L4), a hydroxy and a phenyl (L5) or a hydroxy and a pyrid-6-yl group. These catalysts were compared with the known HEC [Co(appy)Br]Br. Photo- and electrochemistry showed a distinct influence of the bridging position on rates and stabilities of the hydrogen evolution reaction (HER). Apolar ligands resulted in inferior catalytic performance as compared to HECs with polar substituents. Electrochemically, [Co(L1)Br2] was shown to be converted to [Co(L2)Br2] in catalysis. The best catalyst made more than 10’000 turnovers, albeit at an overpotential of 600 mV. Additional pH dependent mechanistic aspects were elucidated by cyclic voltammetry.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
08 Research Priority Programs > Solar Light to Chemical Energy Conversion
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Catalysis
Life Sciences > Biochemistry
Life Sciences > Drug Discovery
Physical Sciences > Physical and Theoretical Chemistry
Physical Sciences > Organic Chemistry
Physical Sciences > Inorganic Chemistry
Uncontrolled Keywords:Inorganic Chemistry, Organic Chemistry, Physical and Theoretical Chemistry, Drug Discovery, Biochemistry, Catalysis
Language:English
Date:1 March 2022
Deposited On:13 Apr 2022 06:16
Last Modified:27 Jun 2024 01:37
Publisher:Wiley Open Access
ISSN:1522-2675
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1002/hlca.202100237
Project Information:
  • : FunderSNSF
  • : Grant IDCRSII2_160801
  • : Project TitlePhotocatalytic Processes at Solvated Interfaces
  • Content: Published Version
  • Licence: Creative Commons: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)