Photochemistry of N ‐Phenyl Benzonaphthothiophene and Dinaphthothiophene Sulfoximines

The sequential photorelease of nitrenes and atomic oxygen [O( 3 P)] is a rare photochemical phenomenon by which two reactive intermediates can be released from a single chromophore. This reactivity has been previously demonstrated in dibenzothiophene (DBT) sulfoximines. We expand the chromophore framework to benzonaphthothiophene (BNT) and dinaphthothiophene (DNT) N ‐phenyl sulfoximine systems to investigate how π‐system extension and electronic effects influence photochemical behavior. Benzonaphthothiophene derivatives bearing electron‐donating and electron‐withdrawing substituents were synthesized to probe electronic effects on photoactivity. Photochemical characterization revealed that DNT‐based scaffolds exhibit significantly enhanced reactivity, with quantum yields of sulfoxide formation approaching threefold higher than those observed for unsubstituted BNT analogs. Electron‐donating/withdrawing group‐substituted BNT derivatives showed moderate increases in quantum yield, indicating that electronic tuning provides incremental improvements relative to chromophore expansion. Spectroscopic measurements show that DNT derivatives display pronounced redshifted absorption and emission profiles with lower singlet excited‑state energies, consistent with increased π‑delocalization. Mechanistic studies, including nitrene trapping, triplet sensitization, and time‑resolved kinetics, support a stepwise photodecomposition pathway involving initial S─N cleavage to form nitrene intermediates followed by S─O bond cleavage to generate O( 3 P). Overall, these findings demonstrate that chromophore extension is a more effective strategy than simple electronic substitution for enhancing reductive photodeimination of aryl sulfoximines.