Green-Emitting Extended B 3 ,N 2 -Doped Polycyclic Aromatic Hydrocarbon with Multiple Resonance Structure.

An air-stable B 3 ,N 2 -PAH ( B 3 N 2 ; nine annulated six-membered rings) was synthesized from 1-X-2,6-di(azasilaanthryl)benzenes (X = Cl, I) via lithiation/borylation, electrophilic aromatic borylation, and Si/B exchange. The heteroatom distribution in B 3 N 2 meets the requirements for multiple resonance thermally activated delayed fluorescence (MR-TADF). Indeed, B 3 N 2 emits green light (λ em = 523 nm; Φ PL = 85%; CHCl 3 ) with a small fwhm of 0.15 eV. Lifetimes for prompt (7.8 ns) and delayed (60 μs) fluorescence were measured in PMMA.