Engineering Cyanoarene Photocatalysts to Resolve Deactivation Challenges in Organocatalyzed ATRP

Abstract Cyanoarene‐based photocatalysts (PCs) have been widely utilized in organic transformations including photo‐mediated controlled radical polymerization (CRP). Despite favorable photophysical and electrochemical properties, these PCs have exhibited limited efficacy in photoinduced organocatalyzed ATRP (O‐ATRP). We identified that reduced performance arises from preferential formation of [PC •+… Br − ] complexes, which facilitates detrimental back electron transfer (BET), generating bromine radicals and side reactions. To address this, we developed a new cyanoarene‐based PC, 4DMDP‐IPN, incorporating strongly electron‐donating groups at donor moieties. This design effectively suppresses complex formation and alleviates BET, significantly improving O‐ATRP performance. With 4DMDP‐IPN, O‐ATRP of methacrylates with high monomer conversion, narrow dispersity, and excellent chain‐end fidelity, even at an ultra‐low PC loading of 5 ppm. This represents the lowest reported PC loading that still ensures polymerization control, eliminating the need for post‐polymerization catalyst removal. Moreover, we demonstrated successful O‐ATRP of poly(methyl acrylate), a particularly challenging monomer, with decent levels of control and chain‐end fidelity. This work not only overcomes intrinsic limitations of cyanoarene‐based PCs in O‐ATRP, but also establishes a new design strategy for next‐generation PCs. We anticipate that these findings will contribute significantly to the advancement of photo‐CRP and broaden the applicability of cyanoarene‐based PCs in a wide range of organic transformations.