Dibenzo‐ peri ‐Heptacene: A Stable Open‐Shell Graphene Fragment With a Balanced Combination of Armchair and Zigzag Edge Structures

Abstract Atomically precise open‐shell graphene fragments, such as extended peri ‐acenes, hold significant interest for electronics and spintronics. However, their inherent high reactivity poses challenges for synthesis and application. In this study, a novel approach is introduced: the fusion of a zigzag‐edged peri ‐tetracene with an all‐armchair‐edged hexa‐ peri ‐hexabenzocoronene (HBC) via two shared benzene rings to produce a stable open‐shell hydrocarbon, named dibenzo‐ peri ‐heptacene (DBPH). The DBPH derivative 1 exhibits considerably enhanced stability, with a half‐life ( t _1/2 ) of 46 days in toluene solution under ambient conditions. This improved stability is attributed to peri ‐benzannulation, enhanced aromatic stabilization, and kinetic protection of the reactive sites along the zigzag edges. The structure of 1 is unequivocally verified through single‐crystal X‐ray diffraction analysis. With a balanced combination of armchair and zigzag edge structures, derivative 1 displays a diradical character of 39.2% and a singlet‐triplet gap of ≈−3.16 kcal mol ⁻¹ . It features a narrow electrochemical energy gap (0.87 eV) and exhibits amphoteric redox behavior. Notably, its dication and dianion states manifest a closed‐shell singlet ground state, representing doubly charged structures where a HBC unit is fused with a benzo[ f ]tetraphene moiety. This research paves the way for synthesizing novel open‐shell graphene fragments with adjustable electronic properties and exceptional stability.