Persistent Halogenated Perylenediimide Organic Radical Anions Orchestrating Three-Photon Energy Conversion and...

Persistent radical ions capable of sequential photon harvesting have remained rare due to their inherent instability. Here we report a halogen-engineered perylenediimide radical anion (PDI-Br₈ ^•‒) that exhibits exceptional air stability (>18 months) while maintaining broad and intense absorption across the visible spectrum (200-800 nm). This electronically delocalized radical displays reversible two-electron redox cycling and an extended excited-state lifetime (∼2 ns), enabling a self-sustained, three-photon, double Z-scheme photocatalytic process. At ultralow (∼ 100 ppm) loading, PDI-Br₈ ^•‒ efficiently catalyzed the one-pot, stereoselective coupling of terminal alkynes, acrylonitrile, and bromotrihalomethanes (CBrX₃; X = Br, Cl, F) to afford (E)-enenitriles under ambient conditions. Bromine substitution might have stabilized the unpaired spin and mitigated charge recombination, transforming an otherwise transient radical into a photochemically robust catalyst. This work establishes a molecular blueprint for multi-photon radical photochemistry, unifying energy storage, charge transport, and synthetic reactivity within a single organic framework.