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Shedding Light on the Oxidizing Properties of Spin-Flip Excited States in a CrIII Polypyridine Complex and Their Use in Photoredox Catalysis

Bürgin, Tobias H. and Glaser, Felix and Wenger, Oliver S.. (2022) Shedding Light on the Oxidizing Properties of Spin-Flip Excited States in a CrIII Polypyridine Complex and Their Use in Photoredox Catalysis. Journal of the American Chemical Society, 144 (31). pp. 14181-14194.

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Abstract

The photoredox activity of well-known RuII complexes stems from metal-to-ligand charge transfer (MLCT) excited states, in which a ligand-based electron can initiate chemical reductions and a metal-centered hole can trigger oxidations. CrIII polypyridines show similar photoredox properties, although they have fundamentally different electronic structures. Their photoactive excited state is of spin-flip nature, differing from the electronic ground state merely by a change of one electron spin, but with otherwise identical d-orbital occupancy. We find that the driving-force dependence for photoinduced electron transfer from 10 different donors to a spin-flip excited state of a CrIII complex is very similar to that for a RuII polypyridine, and thereby validate the concept of estimating the redox potential of d3 spin-flip excited states in analogous manner as for the MLCT states of d6 compounds. Building on this insight, we use our CrIII complex for photocatalytic reactions not previously explored with this compound class, including the aerobic bromination of methoxyaryls, oxygenation of 1,1,2,2-tetraphenylethylene, aerobic hydroxylation of arylboronic acids, and the vinylation of N-phenyl pyrrolidine. This work contributes to understanding the fundamental photochemical properties of first-row transition-metal complexes in comparison to well-explored precious-metal-based photocatalysts.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Wenger)
UniBasel Contributors:Wenger, Oliver and Bürgin, Tobias Hendrik and Glaser, Felix
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
ISSN:0002-7863
e-ISSN:1520-5126
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
edoc DOI:
Last Modified:28 Sep 2022 06:23
Deposited On:28 Sep 2022 06:23

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