N-Annulated 5helicene (NH5) and its dibenzo-extended derivatives are synthesized by cycloisomerization and Scholl-type cyclodehydrogenation methods, respectively. Nitrogen-bridging of fjord-carbons 1 and 14 of 5helicene endows saddle-like NH5 featuring an antiaromatic azepine core with enhanced orbital overlap between nitrogen and the carbon π-system. N-Annulation results in less stabilized HOMO, a smaller HOMO-LUMO energy gap, red-shifted absorption, fluorescence, paratropic ring current over the azepine unit, and tunable aromaticity of the core relative to pristine 5helicene. The NH5 derivatives exhibit space-charge-limited current hole mobility on the order of 10-3 cm2 V-1 s-1, which is higher than that of N-annulated PAH, like N-annulated perylene.
Saha et al. (2026) studied this question.