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.
Dinda et al. (2026) studied this question.