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Abstract Diffusion‐limited kinetics is a key mechanistic debate when consecutive photoelectron transfer (conPET) is discussed in photoredox catalysis. In situ generated organic photoactive radicals can access catalytic systems as reducing as alkaline metals that can activate remarkably stable bonds. However, in many cases, the extremely short‐lived transient nature of these doublet state open‐shell species has led to debatable mechanistic studies, hindering adoption and development. Herein, we document the use of an isolated and stable neutral organicnPrDMQA radical as a highly photoreducing species. The isolated radical offers a unique platform to investigate the mechanism behind the photocatalytic activity of organic photocatalyst radicals. The involvement of reduced solvent is observed, formed by single electron transfer (SET) between the short‐lived excited statenPrDMQA radical and the solvent. In our detailed mechanistic studies, spectroscopic and chemical affirmation of solvent reduction is strongly evident. Reduction of aryl halides, including difluoroarenes is presented as a model study of the conPET method. Further, the activation of N2O, a greenhouse gas that is yet to be activated by photoredox catalysis, is showcased in the absence of a transition metal.
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Perovskite Photocatalytic CO 2 Reduction or Photoredox Organic Transformation?
Abstract Metal‐halide perovskites have been explored as photocatalysts for CO2reduction. We report that perovskite photocatalytic CO2reduction in organic solvents is likely problematic. Instead, the detected products (i.e., CO) likely result from a photoredox organic transformation involving the solvent. Our observations have been validated using isotopic labeling experiments, band energy analysis, and new control experiments. We designed a typical perovskite photocatalytic setup in organic solvents that led to CO production of up to ≈1000 μmol g−1 h−1. CO2reduction in organic solvents must be studied with extra care because photoredox organic transformations can produce orders of magnitude higher rate of CO or CH4than is typical for CO2reduction routes. Though CO2reduction is not likely to occur, in situ CO generation is extremely fast. Hence a suitable system can be established for challenging organic reactions that use CO as a feedstock but exploit the solvent as a CO surrogate.
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- Award ID(s):
- 2140261
- PAR ID:
- 10371936
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 61
- Issue:
- 39
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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