Peri‐acenes are good model compounds for zigzag graphene nanoribbons, but their synthesis is extremely challenging owing to their intrinsic open‐shell diradical character. Now, the successful synthesis and isolation of a stable peri‐tetracene derivative PT‐2ClPh is reported; four 2,6‐dichlorophenyl groups are attached onto the most reactive sites along the zigzag edges. The structure was confirmed by X‐ray crystallographic analysis and its electronic properties were systematically investigated by both experiments and theoretical calculations. It exhibits an open‐shell singlet ground state with a moderate diradical character (y₀=51.5 % by calculation) and a small singlet–triplet gap (ΔE_S‐T=−2.5 kcal mol⁻¹ by SQUID measurement). It displays global aromatic character, which is different from the smaller‐size bisanthene analogue BA‐CF3.

中文翻译：

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并四茂铁基双自由基：合成与性能

i并苯是曲折形石墨烯纳米带的良好模型化合物，但由于其固有的开壳双自由基特性，其合成极具挑战性。现在，已经报道了稳定的并四苯衍生物PT-2ClPh的成功合成和分离。四个2,6-二氯苯基基团沿着锯齿形边缘连接到反应性最高的位点上。通过X射线晶体学分析证实了该结构，并通过实验和理论计算系统地研究了其电子性能。它表现出开壳的单重态基态，具有适度的双自由基特征（根据计算，y ₀ = 51.5％）和小的单重态-三重态间隙（ΔE _S-T = -2.5 kcal mol ^-1通过SQUID测量）。它显示出整体的芳香特性，这与较小尺寸的联蒽类似物BA-CF3不同。