Molecular Design of Donor‐Acceptor‐Type Organic Photocatalysts for Metal‐free Aromatic C−C Bond Formations under Visible Light

Abstract Metal‐free and photocatalytic radical‐mediated aromatic C−C bond formations offer a promising alternative pathway to the conventional transition metal‐catalyzed cross‐coupling reactions. However, the formation of aryl radicals from common precursors such as aryl halides is highly challenging due to their extremely high reductive potential. Here, we report a structural design strategy of donor‐acceptor‐type organic photocatalysts for visible light‐driven C−C bond formations through the reductive dehalogenation of aryl halides. The reduction potential of the photocatalysts could be systematically aligned to be −2.04 V vs. SCE via a simple heteroatom engineering of the donor‐acceptor moieties. The high reductive potential of the molecular photocatalyst could reduce various aryl halides into aryl radicals to form the C−C bond with heteroarenes. The designability of the molecular photocatalyst further allowed the synthesis of a high LUMO (lowest unoccupied molecular orbital) polymer photocatalyst by a self‐initiated free radical polymerization without compromising its LUMO level. magnified image