Amplified Circularly Polarized Luminescence via Torsion Angle Engineering in Carbonyl-N Embedded Hetero[7]helicenes

Helicenes with circularly polarized luminescence (CPL) have attracted increasing interest due to their potential application in chiroptical devices. Thus, it is significant to develop helicene based materials that simultaneously exhibit large luminescence dissymmetry factors (glum) and high photoluminescence quantum yields (ΦPL). Herein, chiral carbonyl-N embedded hetero[7]helicenes incorporating axially chiral binaphthyl are synthesized through acid catalyzed intramolecular electrophilic cyclization reaction and separated via diastereomer resolution. Single-crystal X-ray diffraction analysis confirms that the insertion of peripheral carbon atoms significantly enlarges the total torsion angles within the inner helix of the hetero[7]helicene framework. Thanks to the twist carbonyl-N embedded helical skeleton, the hetero[7]helicenes exhibit intense CPL signals with |glum| of 2.6 × 10−3 and CPL brightness (BCPL) up to 20 M−1 cm−1, demonstrating that the |glum| values can be efficiently amplified via diastereomeric configuration regulation and total torsion angle engineering.