Birch-Type-Reduced Carbazole Anions Enable Redox-Adaptive Super-Reducing Photocatalysis

Abstract

Abstract Photocatalytic activation of inert chemical bonds is constrained by the redox potential of the catalyst. Here, we report a redox-adaptive photocatalytic strategy in which an electron-rich carbazole photocatalyst, CBZ6, functions as a molecular redox transformer through the formation of Birch-type carbazole anions. Under visible light, CBZ6 switches between a neutral state for conventional photoredox reactions and an anionic state for super-reducing catalysis. Excitation of the anionic state generates a super-reducing species with an excited-state oxidation potential of approximately −3.6 V versus SCE, substantially beyond that of the neutral excited state (−2.2 V). This adaptive redox switching enables activation of otherwise inaccessible C–F bonds in aryl fluorides, polyfluoroalkyl compounds, and fluoropolymers. The complementary reactivities of the two states further enable diverse photoredox transformations, establishing redox adaptation as a strategy for expanding the accessible reactivity of organic photocatalysts.