Green-Emitting Extended B₃,N₂-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 (lambda(em) = 523 nm; Phi(PL) = 85%; CHCl3) with a small fwhm of 0.15 eV. Lifetimes for prompt (7.8 ns) and delayed (60 mu s) fluorescence were measured in PMMA.