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  • Undecabenzo[7]superhelicene...
    Cruz, Carlos M.; Castro‐Fernández, Silvia; Maçôas, Ermelinda; Cuerva, Juan M.; Campaña, Araceli G.

    Angewandte Chemie International Edition, November 5, 2018, Volume: 57, Issue: 45
    Journal Article

    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 undecabenzo7carbohelicene. The described compound is the first fully π‐extended 7helicene. 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. A twist in the ribbon: A chiral helical nanographene with a central 7helicene unit was synthesized and its enantiomers isolated and studied. Both enantiomers of the undecabenzo7superhelicene exhibit remarkable chiroptical and non‐linear optical properties, with a two‐photon absorption cross‐section of 870 GM at 800 nm and a perfect overlap between linear, non‐linear, and chiral emissions. CPL=circularly polarized luminescence.