Polymer-supported photosensitizers for oxidative organic transformations in flow and under visible light irradiation

• John M. Tobin^†
• Timothy J. D. McCabe^‡
• Andrew W. Prentice^†
• Sarah Holzer^†
• Gareth O. Lloyd^†
• Martin J. Paterson^†
• Valeria Arrighi^†
• Peter A. G. Cormack^‡
• Filipe Vilela^†

• ^† School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS Scotland, United Kingdom
• ^‡ WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL Scotland, United Kingdom

A 2,1,3-benzothiadiazole (BTZ)-based vinyl cross-linker was synthesized and copolymerized with large excesses of styrene using free radical polymerization to deliver heterogeneous triplet photosensitizers in three distinct physical formats: gels, beads, and monoliths. These photosensitizers were employed for the production of singlet oxygen (1O2) and for the aerobic hydroxylation of arylboronic acids via superoxide radical anion (O2•–), whereby the materials demonstrated good chemical and light stability. BTZ-containing beads and monoliths were exploited as photosensitizers in a commercial flow reactor, and 1O2 production was also demonstrated using direct sunlight irradiation, with a conversion rate comparable to the rates achieved when a 420 nm LED module is used as the source of photons.

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