Hexabenzoheptacene: A Longitudinally Multihelicene Nanocarbon with Local Aromaticity and Enhanced Stability

Abstract

AbstractWe report the synthesis of a longitudinally helical molecular nanocarbon, hexabenzoheptacene (HBH), along with its dimethylated derivative (HBH‐Me), which are composed of six benzene rings periodically benzannulated to both zigzag edges of a heptacene core. This benzannulation pattern endows the resulting nanocarbons with a helical heptacene core and local aromaticity, imparting enhanced solubility and stability to the system. The chiral HBH‐Me adopts a more highly twisted conformation with an end‐to‐end twist angle of 95°, enabling the separation of the enantiomers. Both HBH and HBH‐Me can be facilely oxidized into their corresponding dications, which exhibit enhanced planarity and aromaticity upon loss of electrons. Notably, both longitudinally helical nanocarbons readily promote solid state packing into two‐dimensional (2D) arrangement. Single‐crystal microbelts of HBH‐Me show hole mobility up to 0.62 cm2 V−1 s−1, illustrating the promising potential of these longitudinally helical molecules for organic electronic devices.