Nonplanar S-Shaped Bisanthene: Synthesis, Structures, and Properties

Spiro-fused polycyclic aromatic compounds have attracted increasing attention. In this work, we designed a nonplanar S-shaped compound hel-BA featuring dual [4]helicene. Its synthesis adopts an efficient cationic radical-mediated direct C–H aromatic nucleophilic substitution. X-ray diffraction reveals tight columnar stacking, with its photoluminescence quantum yield in the powder state being 28%. hel-BA displays reversible multiple redox, with the charged states showing near-infrared (NIR) absorption and promising NIR electrochromic materials. These results provide a new perspective on extended helicenes.