Antiaromatic 1,5‐Diaza‐ s ‐indacenes

s ‐Indacene is a classical non‐alternant hydrocarbon that contains 12 π‐electrons in a cyclic π‐conjugation system. Herein, we report its nitrogen‐doped analogue, 1,5‐diaza‐ s ‐indacene. 1,5‐Diaza‐ s ‐indacenes were readily prepared from commercially available 2,5‐dichlorobenzene‐1,4‐diamine through a two‐step transformation consisting of a palladium‐catalyzed Larock cyclization with diaryl acetylenes followed by hydrogen abstraction. The thus obtained 1,5‐diaza‐ s ‐indacenes exhibited distinct antiaromaticity, as manifested in clear bond‐length alternation, a forbidden HOMO–LUMO transition, and a paratropic ring current. As compared to the parent s ‐indacene, the 1,5‐diaza‐ s ‐indacenes showed higher electron‐accepting ability owing to the presence of imine‐type nitrogen atoms. The 1,5‐diaza‐ s ‐indacene core is effectively conjugated with the peripheral aryl groups, which enables fine‐tuning of the absorption spectra and redox properties. The two possible localized forms of 1,5‐diaza‐ s ‐indacene were compared in terms of their energetic aspects.