The helical elongation of π-extended diazahelicenes with amplified circularly polarized luminescence

Helicenes are circularly polarized luminescence (CPL)-active but suffer from a fundamental tradeoff between fluorescence quantum yield (Φ_F) and luminescence dissymmetry factor (|g_lum|). Herein, we present a strategy combining lateral π-extension and helical elongation in carbazole-embedded helicenes to address this challenge. Specifically, π-extended diaza[7]helicene (1) and diaza[9]helicene (2) were synthesized and characterized, revealing nearly a 2-fold increase in Φ_F and a 6-fold enhancement in |g_lum| from 1 to 2. This approach offers a new pathway for high-performance CPL emitters.