A π‐Extended Pentadecabenzo[9]Helicene

A novel chiral nanographene (i.e. EP9H) with a pentadecabenzo[9]helicene core fragment has been synthesized and fully characterized. Single‐crystal X‐ray diffraction unambiguously confirms the helical structure. The fluorescence emission of EP9H is located in the near infrared region (λem=684 nm) with a medium quantum yield (0.10) for helicene derivatives. Cyclic voltammetry reveals its seven quasi‐reversible redox states from −2 to +5. Furthermore, enantiopure EP9H displays distinct CD signals in a broad spectral range from 300 to 700 nm. Notably, compared to the reported small organic molecules, EP9H displays an outstanding |glum| value of 4.50×10−2 and BCPL as 304 M−1 cm−1. A chiral bilayer nanographene (EP9H) containing a pentadecabenzo[9]helicene core fragment has been synthesized with an extended π‐system perpendicular to the helical axis of [9]helicene. Furthermore, the structure extension induced significant improvements in the fluorescence quantum yield and circularly polarized luminescence, as evident from the large glum and BCPL values.