Shaikh Aslam C, Hossain Md Mubarak, Moutet Jules, Kumar Anshu, Thompson Benjamin, Huxter Vanessa M, Gianetti Thomas L
Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States.
Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab, 140001, India.
Angew Chem Int Ed Engl. 2025 Feb 24;64(9):e202420483. doi: 10.1002/anie.202420483. Epub 2025 Jan 20.
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 organic PrDMQA 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 state PrDMQA 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 NO, a greenhouse gas that is yet to be activated by photoredox catalysis, is showcased in the absence of a transition metal.
在光氧化还原催化中讨论连续光电子转移（conPET）时，扩散限制动力学是一个关键的机理争议点。原位生成的有机光活性自由基可以进入催化体系，其还原能力可与碱金属相当，能够活化非常稳定的化学键。然而，在许多情况下，这些双态开壳物种极短的瞬态性质导致了有争议的机理研究，阻碍了其应用和发展。在此，我们记录了使用一种分离且稳定的中性有机PrDMQA自由基作为一种高还原能力的物种。这种分离的自由基提供了一个独特的平台来研究有机光催化剂自由基光催化活性背后的机理。观察到通过短寿命激发态PrDMQA自由基与溶剂之间的单电子转移（SET）形成了还原态溶剂。在我们详细的机理研究中，溶剂还原的光谱和化学确证非常明显。作为conPET方法的模型研究，展示了包括二氟芳烃在内的芳基卤化物的还原。此外，在没有过渡金属的情况下，展示了尚未被光氧化还原催化活化的温室气体NO的活化。
