Thus, we performed DFT calculations and found that all azaheptalenes have much higher racemization barriers (E calc /kcal mol -1 = 50.5 for 1, 50.7, for 2, and 50.9 for 3) (Figures and) than those for helical nanographene with a 6-7-7-6 ring system (E calc /kcal mol -1 = 29.2) and N-centered [4]helicene with a 6-6-6-6 ring system (E calc /kcal mol -1 = 32.7). Thus, we concluded that the theoretically obtained barrier of ca. 50 kcal mol -1 is reasonable for these systems. In the case of radical cation 3 +• , DFT calculations [B3LYP/6-31G(d,p)] revealed a smaller racemization barrier (E calc /kcal mol -1 = 40.1 for 3 +• ) (Figure ), which can be accounted for by the decreased torsion upon oxidation. In conclusion, we designed helical azaheptalenes 1-3 with a contiguous 6-7-7-6 ring system, which could be efficiently synthesized by a palladium-catalyzed one-pot reaction. Regardless of these azaheptalenes composed of a minimal number of fused rings, its helicity exhibits sufficient configurational stablity to be separated using chiral HPLC. Moreover, thanks to the electron-donating nitorogen atom, such helical azaheptalene 3 undergoes one-electron oxidation to produce radical cation species with a chiroptical response. Notably, a larger g abs value was observed in the UV region for neutral azaheptalene 3 with P or M helicity, and its radical cation (P) or (M)-3 +• SbCl 6 -exhibited obvious CD signals extending to the NIR region. Therefore, helical azaheptalene, the chiroptical properties of which can be switched by an electric potential, may help to pave the way for the development of stimuli-responsive materials.