Issue 27, 2021

Photomediated core modification of organic photoredox catalysts in radical addition: mechanism and applications

Abstract

Dihydrophenazines and their analogues have been widely used as strong reducing photoredox catalysts in radical chemistry, such as organocatalyzed atom transfer radical polymerization (O-ATRP). However, when dihydrophenazines were employed as organic photoredox catalysts (OPCs) to mediate O-ATRP, the initiator efficiency was nonquantitative due to cross-coupling between dihydrophenazines and radical species. Here, a new kind of core modification for dihydrophenazines, phenoxazines and phenothiazines was developed through this cross-coupling process. Mechanistic studies suggested that the radical species would be more likely to couple with OPC' radical cations rather than the ground-state OPC. Core modification of OPCs could stabilize the radical ions in an oxidative quenching catalytic cycle. Significantly, core modifications of OPCs could lower the energy of light required for photoexcitation. Compared with their noncore-modified counterparts, all the core-modified dihydrophenazines and phenoxazines exhibited efficient performance in controlling O-ATRP for the synthesis of poly(methyl methacrylate) with higher initiator efficiencies under the irradiation of simulated sunlight.

Graphical abstract: Photomediated core modification of organic photoredox catalysts in radical addition: mechanism and applications

Supplementary files

Article information

Article type
Edge Article
Submitted
23 Apr 2021
Accepted
08 Jun 2021
First published
10 Jun 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 9432-9441

Photomediated core modification of organic photoredox catalysts in radical addition: mechanism and applications

Y. Zhang, D. Jiang, Z. Fang, N. Zhu, N. Sun, W. He, C. Liu, L. Zhao and K. Guo, Chem. Sci., 2021, 12, 9432 DOI: 10.1039/D1SC02258J

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