Chiral Distorted Hexa-peri-hexabenzocoronenes Bearing a Nonagon-Embedded Carbohelicene.

Abstract

A new family of chiral saddle‐helix hybrid nanographenes is reported. The first hexa‐peri‐hexabenzocoronene (HBC) analogues bearing a nine‐membered carbocycle are presented. Furthermore, for the first time, π‐extended carbo[n]helicenes containing a nine‐membered ring as part of the helical moiety have been synthesized. The combination of a [5]helicene moiety and a nonagon ring in a single chiral motif induces a tremendous distortion from planarity into the nanographenic structures compared to other saddle‐helix hybrids such as heptagon‐ and octagon‐containing π‐extended carbo[5]helicenes. In fact, the interplanar angle of the two terminal rings reaches the largest angle (134.8°) of a carbohelicene reported to date, thus being by far the most twisted helicene yet prepared. Photophysical properties evaluation showed improved absorption dissymmetry factors (|g abs|=4.2×10−3) in the new family of nonagon‐containing π‐extended carbo[5]helicenes.