Exploiting Charge-Transfer States for Maximizing Intersystem Crossing Yields in Organic Photoredox Catalysts

A key feature of prominent transition-metal-containing photoredox catalysts (PCs) is high quantum yield access to long-lived excited states characterized by a change in spin multiplicity. For organic PCs, challenges emerge for promoting excited-state intersystem crossing (ISC), particularly when pot...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2018-04, Vol.140 (14), p.4778-4781
Main Authors: Sartor, Steven M, McCarthy, Blaine G, Pearson, Ryan M, Miyake, Garret M, Damrauer, Niels H
Format: Article
Language:English
Subjects:
Catalysis
Molecular Structure
Organometallic Compounds - chemistry
Oxidation-Reduction
Photochemical Processes
Quantum Theory
Transition Elements - chemistry
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Summary:A key feature of prominent transition-metal-containing photoredox catalysts (PCs) is high quantum yield access to long-lived excited states characterized by a change in spin multiplicity. For organic PCs, challenges emerge for promoting excited-state intersystem crossing (ISC), particularly when potent excited-state reductants are desired. Herein, we report a design exploiting orthogonal π-systems and an intermediate-energy charge-transfer excited state to maximize ISC yields (ΦISC) in a highly reducing (E 0* = −1.7 V vs SCE), visible-light-absorbing phenoxazine-based PC. Simple substitution of N-phenyl for N-naphthyl is shown to dramatically increase ΦISC from 0.11 to 0.91 without altering catalytically important properties, such as E 0*.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.8b01001