One-Step Intermolecular Oxidative Coupling and Cyclodehydration Strategy for Pure-Green B,N,O-Embedded Hetero[9]Helicene Emitter.

Helicenes are promising circularly polarized luminescence (CPL) candidates owing to their inherent chirality. In particular, B,N-embedded heterohelicenes achieve superior exciton utilization via multiple-resonance thermally activated delayed fluorescence, whereas their syntheses remain challenging. Herein, we present a facile strategy of one-step intermolecular oxidative coupling and cyclodehydration to achieve the concise synthesis of a B,N,O-embedded hetero[9]helicene (BNFN). BNFN exhibits narrowband green photoluminescence peaking at 516 nm with a rapid reverse intersystem crossing rate (3.76 × 105 s-1), and the enantiomers display intense CPL with dissymmetry factors (gPL) of +2.4/-2.6 × 10-3. Corresponding circularly polarized organic light-emitting diodes (CP-OLEDs) deliver CIE coordinates of (0.20, 0.72) and gEL of +3.4/-3.3 × 10-3. Notably, these devices demonstrate maximum external quantum efficiencies of 31.3%/30.2% and low efficiency roll-off. This work paves the way toward the development of a novel B,N-embedded heterohelicene for efficient CP-OLEDs.