Issue 29, 2021

Sensitization-initiated electron transfer via upconversion: mechanism and photocatalytic applications

Abstract

Sensitization-initiated electron transfer (SenI-ET) describes a recently discovered photoredox strategy that relies on two consecutive light absorption events, triggering a sequence of energy and electron transfer steps. The cumulative energy input from two visible photons gives access to thermodynamically demanding reactions, which would be unattainable by single excitation with visible light. For this reason, SenI-ET has become a very useful strategy in synthetic photochemistry, but the mechanism has been difficult to clarify due to its complexity. We demonstrate that SenI-ET can operate via sensitized triplet–triplet annihilation upconversion, and we provide the first direct spectroscopic evidence for the catalytically active species. In our system comprised of fac-[Ir(ppy)3] as a light absorber, 2,7-di-tert-butylpyrene as an annihilator, and N,N-dimethylaniline as a sacrificial reductant, all photochemical reaction steps proceed with remarkable rates and efficiencies, and this system is furthermore suitable for photocatalytic aryl dehalogenations, pinacol couplings and detosylation reactions. The insights presented here are relevant for the further rational development of photoredox processes based on multi-photon excitation, and they could have important implications in the greater contexts of synthetic photochemistry and solar energy conversion.

Graphical abstract: Sensitization-initiated electron transfer via upconversion: mechanism and photocatalytic applications

Supplementary files

Article information

Article type
Edge Article
Submitted
14 apr 2021
Accepted
16 iyn 2021
First published
01 iyl 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 9922-9933

Sensitization-initiated electron transfer via upconversion: mechanism and photocatalytic applications

F. Glaser, C. Kerzig and O. S. Wenger, Chem. Sci., 2021, 12, 9922 DOI: 10.1039/D1SC02085D

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