Undecabenzo[7]superhelicene: A Helical Nanographene Ribbon as a Circularly Polarized Luminescence Emitter

The synthesis and characterization of an enantiopure superhelicene nanographene is reported in which two saddle‐shaped and one planar hexabenzocoronene (HBC) units are arranged in a helicoidal shape to form an undecabenzo[7]carbohelicene. The described compound is the first fully π‐extended [7]helicene. Racemic resolution of the helical nanographene permitted analysis of the chiroptical properties and revealed dissymmetry factors in the range of 2×10 −3 both in the absorption and in the emission measurements. Remarkably, non‐linear photophysical analysis demonstrated a two‐photon absorption cross‐section of 870 GM at 800 nm and a perfect overlap between linear, non‐linear, and chiral emissions.