Non-Alternant Helical Bilayer Molecular Carbons Bearing a Diaza[9]Helicene with Enhanced Emission and Circularly...

Helical bilayer molecular carbons have attracted considerable attention due to their distinct physicochemical properties. However, constrained by the limited structural diversity, helical bilayer molecular carbons typically exhibit low quantum yields and low circularly polarized luminescence (CPL) brightness, which limits their potential applications as CPL emitters. In this work, helical bilayer molecular carbons (NDPH and NDPBu) featuring a heptagon-embedded diaza[9]helicene were successfully synthesized employing ring expansion strategy. The incorporated heptagons enhance the highly twisted and rigid bilayer geometry with a significant interlayer interaction index δ_g (18.6), while the introduction of carbazole units yields a high fluorescence quantum yield (Φ_F = 74%). As a result, the resultant enantiomers exhibit pronounced electronic circular dichroism and CPL responses with a high CPL brightness (B_CPL) value of 112 M^-1 cm^-1. In addition, an organic light-emitting diode (OLED) device was fabricated employing NDPH as dopant, achieving a maximum external quantum efficiency (η_EQE,max) of 3.6%, which demonstrates its potential optoelectronic application.