Persistent Halogenated Perylenediimide Organic Radical Anions Orchestrating Three‐Photon Energy Conversion and Programmable Molecular Coupling

ABSTRACT 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‐Br 8 •‒ ) 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‐Br 8 •‒ efficiently catalyzed the one‐pot, stereoselective coupling of terminal alkynes, acrylonitrile, and bromotrihalomethanes (CBrX 3 ; 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.