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Published on: May 21, 2019
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Excited Organic Radicals in Photoredox Catalysis
Björn Pfund1, Oliver S Wenger1
1Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
JACS Au
|February 28, 2025
Summary
This study questions the photocatalytic role of organic radicals, revealing their rapid decay and potential degradation products. It proposes new pathways for future photocatalysis advancements using excited organic radicals.
Area of Science:
- Organic Chemistry
- Photocatalysis
- Reaction Mechanisms
Background:
- Excited organic radicals are proposed as photoactive species in synthesis.
- Doubts exist regarding their photocatalytic efficiency due to degradation products and rapid excited-state decay (picoseconds).
Purpose of the Study:
- To critically analyze the proposed photocatalytic roles of organic radicals in synthetic transformations.
- To compare theoretical excited-state potentials with required potentials for observed reactivity.
- To investigate the mechanisms behind photoinduced electron transfer in excited radicals.
Main Methods:
- Comparative analysis of theoretical maximum excited-state potentials versus required potentials.
- Summarization of mechanistic studies on similar photocatalysts.
- Kinetic analysis of subpicosecond photoinduced electron transfer.
- Rationalization of anti-Kasha reactivity from higher excited states.
Main Results:
- Skepticism regarding organic radicals as true photocatalysts due to degradation and fast decay.
- Identification of systems where proposed radical photocatalysts exceed theoretical maximum reactivity.
- Evidence of photoinduced electron transfer in excited radicals on subpicosecond timescales.
- Potential for anti-Kasha reactivity from higher excited states with femtosecond lifetimes.
Conclusions:
- The true photocatalytic role of organic radicals requires re-evaluation.
- Understanding ultrafast excited-state dynamics is crucial for developing novel photocatalytic pathways.
- Future advancements may leverage higher excited states for enhanced photocatalysis.
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