Unusual and Persistent Free Radical Intermediate Production from 2-Pyridyl Ketones via UV Irradiation: A Direct ESR Study
Aryl ketones are often used as photosensitizers and photoinitiators. Free radical intermediates have been suggested, but not confirmed, to be generated after photoirradiation. Here we found, unexpectedly, that a persistent radical was produced from di-2-pyridyl ketone after UV irradiation, which was detected by the direct ESR method. Interestingly, the persistent radical was very sensitive to oxygen and the pH of the reaction medium. A similar persistent radical was also observed from phenyl-2-pyridyl ketone, but not from 3-benzoylpyridine, 4-benzoylpyridine, and benzophenone, suggesting that the presence of a carbonyl group connected to the <i>ortho</i>-position of the pyridine ring is critical for such radical production. By complementary applications of ESR, HPLC, and ESI-Q-TOF-MS, the possible chemical structures of the persistent radical and final product were identified, and the possible underlying reaction mechanism was proposed. This represents the first report on UV-induced persistent radical generation from 2-pyridyl ketones, which should be of great significance for future studies.
Authors
- Chun‐Hua Huang (ORCID: https://orcid.org/0000-0001-7158-2149)
- Z. A. Liu (ORCID: https://orcid.org/0009-0004-2608-1977)
- Jie Shao (ORCID: https://orcid.org/0000-0001-9212-9685)
- Jing Chen (ORCID: https://orcid.org/0000-0002-8602-4593)
- Qin Li (ORCID: https://orcid.org/0000-0001-7942-6685)
- Zhihui Zhang (ORCID: https://orcid.org/0000-0003-3111-2665)
- Zhenhuan Li (ORCID: https://orcid.org/0000-0003-4734-2334)
- Li Mao (ORCID: https://orcid.org/0000-0002-1597-5316)
- Lin-Na Xie (ORCID: https://orcid.org/0000-0003-0465-9809)
- Zhi-Guo Sheng
- Bo Shao (ORCID: https://orcid.org/0000-0003-0488-3966)
- Dan Xu (ORCID: https://orcid.org/0000-0002-6031-8542)
- Ben‐Zhan Zhu (ORCID: https://orcid.org/0000-0001-5484-4290)
Institutions
- Zhejiang Chinese Medical University (CN)
- Hong Kong Baptist University (HK)
- Chinese Center For Disease Control and Prevention (CN)
- Research Center for Eco-Environmental Sciences (CN)
- University of Chinese Academy of Sciences (CN)
- Jining Medical University (CN)
Publication Details
- Journal
- The Journal of Physical Chemistry Letters
- Published
- 2024-11-05
- DOI
- https://doi.org/10.1021/acs.jpclett.4c02657
- Citations
- 2
- Primary Topic
- Radical Photochemical Reactions
- Type
- article
- Field-Weighted Citation Impact
- 0.50
Funders
- National Natural Science Foundation of China
- Chinese Academy of Sciences
- Peking University
- Peking University Third Hospital
- Natural Science Foundation of Zhejiang Province