A Mechanistic Study of Halogen Addition and Photoelimination from π-Conjugated Tellurophenes

Carrera, Elisa I.; Lanterna, Anabel E.; Lough, Alan J.; Scaiano, Juan C.; Seferos, Dwight S.

Abstract

The ability to drive reactivity using visible light is of importance for many disciplines of chemistry and has significant implications for sustainable chemistry. Identifying photochemically active compounds and understanding photochemical mechanisms is important for the development of useful materials for synthesis and catalysis. Here we report a series of photoactive diphenyltellurophene compounds bearing electron-withdrawing and electron-donating substituents synthesized by alkyne coupling/ring closing or palladium-catalyzed ipso-arylation chemistry. The redox chemistry of these compounds was studied with respect to oxidative addition and photoelimination of bromine, which is of importance for energy storage reactions involving X2. The oxidative addition reaction mechanism was studied using density functional theory, the results of which support a three-step mechanism involving the formation of an initial η1 association complex, a monobrominated intermediate, and finally the dibrominated product. All of the tellurophene derivatives undergo photoreduction using 430, 447, or 617 nm light depending on the absorption properties of the compound. Compounds bearing electron-withdrawing substituents have the highest photochemical quantum efficiencies in the presence of an alkene trap, with efficiencies of up to 42.4% for a pentafluorophenyl-functionalized tellurophene. The photoelimination reaction was studied in detail through bromine trapping experiments and laser flash photolysis, and a mechanism is proposed. The photoreaction, which occurs by release of bromine radicals, is competitive with intersystem crossing to the triplet state of the brominated species, as evidenced by the formation of singlet oxygen. These findings should be useful for the design of new photochemically active compounds supported by main-group elements.

Citation

Carrera, E. I., Lanterna, A. E., Lough, A. J., Scaiano, J. C., & Seferos, D. S. (2016). A Mechanistic Study of Halogen Addition and Photoelimination from π-Conjugated Tellurophenes. Journal of the American Chemical Society, 138(8), 2678-2689. https://doi.org/10.1021/jacs.5b11649

• Journal Article Type: Article
• Acceptance Date: Feb 7, 2016
• Online Publication Date: Feb 19, 2016
• Publication Date: Mar 2, 2016
• Deposit Date: Jun 22, 2020
• Publicly Available Date: Jul 21, 2020
• Journal: Journal of the American Chemical Society
• Print ISSN: 0002-7863
• Electronic ISSN: 1520-5126
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 138
• Issue: 8
• Pages: 2678-2689
• DOI: https://doi.org/10.1021/jacs.5b11649
• Keywords: Colloid and Surface Chemistry; Biochemistry; General Chemistry; Catalysis
• Public URL: https://nottingham-repository.worktribe.com/output/4701620
• Publisher URL: https://pubs.acs.org/doi/10.1021/jacs.5b11649
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/jacs.5b11649.