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PCET-Based Ligand Limits Charge Recombination with an Ir(III) Photoredox Catalyst.

Authors :
Sayre H
Ripberger HH
Odella E
Zieleniewska A
Heredia DA
Rumbles G
Scholes GD
Moore TA
Moore AL
Knowles RR
Source :
Journal of the American Chemical Society [J Am Chem Soc] 2021 Aug 25; Vol. 143 (33), pp. 13034-13043. Date of Electronic Publication: 2021 Aug 11.
Publication Year :
2021

Abstract

Upon photoinitiated electron transfer, charge recombination limits the quantum yield of photoredox reactions for which the rates for the forward reaction and back electron transfer are competitive. Taking inspiration from a proton-coupled electron transfer (PCET) process in Photosystem II, a benzimidazole-phenol (BIP) has been covalently attached to the 2,2'-bipyridyl ligand of [Ir(dF(CF <subscript>3</subscript> )ppy) <subscript>2</subscript> (bpy)][PF <subscript>6</subscript> ] (dF(CF <subscript>3</subscript> )ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine; bpy = 2,2'-bipyridyl). Excitation of the [Ir(dF(CF <subscript>3</subscript> )ppy) <subscript>2</subscript> (BIP-bpy)][PF <subscript>6</subscript> ] photocatalyst results in intramolecular PCET to form a charge-separated state with oxidized BIP. Subsequent reduction of methyl viologen dication (MV <superscript>2+</superscript> ), a substrate surrogate, by the reducing moiety of the charge separated species demonstrates that the inclusion of BIP significantly slows the charge recombination rate. The effect of ∼24-fold slower charge recombination in a photocatalytic phthalimide ester reduction resulted in a greater than 2-fold increase in reaction quantum efficiency.

Details

Language :
English
ISSN :
1520-5126
Volume :
143
Issue :
33
Database :
MEDLINE
Journal :
Journal of the American Chemical Society
Publication Type :
Academic Journal
Accession number :
34378919
Full Text :
https://doi.org/10.1021/jacs.1c01701