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 (ΦF) and luminescence dissymmetry factor (|glum|). 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 ΦF and a 6-fold enhancement in |glum| from 1 to 2. This approach offers a new pathway for high-performance CPL emitters.