We prepared an electron‐rich p‐quinodimethane compound, 2,9‐dibromo‐7,14‐dimesityl‐5,12‐dioxapentacene (1). The quinoidal character was clarified by bond‐length alternation in the central ring. Clear vibrational structures in both absorption and emission bands and small Stokes shift indicate the rigid dioxapentacene framework. The reversible redox waves of 1 were observed at +0.14 and +0.69 V vs. Fc⁺/Fc, respectively. The radical cation salt 1^⋅+⋅SbF₆⁻ was successfully isolated and characterized by means of X‐ray structural analysis and ESR and UV/Vis‐near infrared absorption spectroscopies. The molecular structure and electronic properties of the neutral and radical cation species were compared to those of the isomeric o‐quinodimethane.

中文翻译：

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与同构邻-邻二甲基甲烷比较的具有两个氧桥的多环对-邻二甲基甲烷的制备，性质及其自由基阳离子

我们制备了一个富电子的对-喹二甲烷化合物，2,9-二溴-7,14-二甲苯基-1,5,12-二氧杂戊并五烯（1）。通过中心环中键长的交替来阐明喹诺酮的特征。吸收带和发射带中清晰的振动结构以及小的斯托克斯位移表明刚性的二氧杂戊并五苯骨架。相对于Fc ⁺ / Fc，分别在+0.14和+0.69 V处观察到1的可逆氧化还原波。自由基阳离子盐1 ^⋅+ ⋅SbF ₆ ^-通过X射线结构分析，ESR和UV / Vis-近红外吸收光谱法成功分离并鉴定了X-射线。将中性和自由基阳离子物种的分子结构和电子性能与邻-喹二甲烷异构体进行了比较。