Extent of carbon nitride photocharging controls energetics of hydrogen transfer in photochemical cascade processes

Graphitic carbon nitride is widely studied in organic photoredox catalysis. Reductive quenching of carbon nitride excited state is postulated in many photocatalytic transformations. However, the reactivity of this species in the turn over step is less explored. In this work, we investigate electron...

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Bibliographic Details
Published in:Nature communications 2023-11, Vol.14 (1), p.7684-7684, Article 7684
Main Authors: Savateev, Oleksandr, Nolkemper, Karlo, Kühne, Thomas D., Shvalagin, Vitaliy, Markushyna, Yevheniia, Antonietti, Markus
Format: Article
Language:English
Subjects:
119/118
140/131
639/301/299/890
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639/638/77/890
Amines
Ammonium
Carbon
Carbon nitride
Catalysis
Cations
Charge transfer
Electron transfer
Electrons
Humanities and Social Sciences
Imines
multidisciplinary
Oxidants
Oxidizing agents
Photocatalysis
Photochemicals
Photoredox catalysis
Protons
Science
Science (multidisciplinary)
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Summary:Graphitic carbon nitride is widely studied in organic photoredox catalysis. Reductive quenching of carbon nitride excited state is postulated in many photocatalytic transformations. However, the reactivity of this species in the turn over step is less explored. In this work, we investigate electron and proton transfer from carbon nitride that is photocharged to a various extent, while the negative charge is compensated either by protons or ammonium cations. Strong stabilization of electrons by ammonium cations makes proton-coupled electron transfer uphill, and affords air-stable persistent carbon nitride radicals. In carbon nitrides, which are photocharged to a smaller extent, protons do not stabilize electrons, which results in spontaneous charge transfer to oxidants. Facile proton-coupled electron transfer is a key step in the photocatalytic oxidative-reductive cascade – tetramerization of benzylic amines. The feasibility of proton-coupled electron transfer is modulated by adjusting the extent of carbon nitride photocharging, type of counterion and temperature. Savateev et al. investigate proton-coupled electron transfer from persistent graphitic carbon nitride radical to oxygen and imines. The results of their study find application in cascade photocatalysis – selective tetramerization of benzylic amines.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-023-43328-6