Octagon?Embedded Carbohelicene as a Chiral Motif for Circularly Polarized Luminescence Emission of Saddle?Helix Nanographenes

We report a new family of hexa-peri-hexabenzocoronene (HBC)-based helical nanographenes incorporating ?-extended carbo[5]helicenes bearing an octagonal carbocycle. This represents kind highly distorted saddle-helix hybrid nanographenes. For the first time, eight-membered ring becomes constituent both carbo[5]helicene and HBC thus, negative curvature is responsible for twisting units. novel chiral motif, namely, oct-[5]helicene results in largest torsion angle recorded so far (?=79.5°), as it has been suggested by DFT-calculations confirmed X-ray crystallography. Consequently, barriers isomerization become exceptionally high [5]helicene unsubstituted fjord region since neither racemization nor decomposition were observed at 200 °C 1 or 3 during 5 h. Therefore, racemic resolutions allowed subsequent chiroptical studies showing ECD CPL responses this