Asymmetric Triple Helical Nonbenzenoid Nanographenes with Controllable Helicene Lengths

Helical nanographenes (NGs) play a crucial role in the development of chiral nanomaterials due to their distinctive optoelectronic and chiroptical properties. Herein, we report the efficient synthesis of two unprecedented azulene-embedded asymmetric triple helical NGs (1 and 2) with controllable helicene subunit lengths and π-extension. The crystallographic analysis confirms their highly twisted and asymmetric geometries. Both compounds exhibit narrow and tunable optical energy gaps (1: 1.74 eV; 2: 1.63 eV), as determined by UV–vis absorption and cyclic voltammetry measurements. Moreover, the enantiomers of 1 display pronounced chiroptical activity with a gabs of up to 3.1 × 10–3.