This study presents an important and efficient synthetic approach to 5,8-dibromo-2,11-di-tert-butylpicene (3), with multigram scale, which was then converted to a new series of picenophanes (6-10). The tub-shaped [2,2](5,8)picenophanediene 8 with two cis-ethylene linkers was explored using X-ray crystallography. The tub-to-tub inversion proceed through the successive bending of the linkers and the barrier for isopropyl-substituted derivative 10 was experimentally estimated to be 18.7 kcal/mol. Picenophanes with a large π-system and semi-rigid structure exhibited anomalous photophysical properties. The ethano-bridged picenophane shows the weak exciton delocalization while the cis-ethylene-bridged picenophane exhibits dual emission rendered by the weakly delocalized exciton and excimer. With the aid of the ultrafast time-resolved emission spectroscopy, the mechanism of the excimer formation is resolved, showing a unique behavior of two-state reversible reaction with fast structural deformation whose lifetime is around 20 ps at 298 K. This work demonstrates that the slight difference in the bridge of tub-shaped picenophanes renders distinct photophysical behavior, revealing the potential of harnessing inter-moiety reaction in the picenophane systems.

中文翻译：

---

[2,2](5,8)Picenophanedienes：合成、结构分析、分子动力学和可逆分子内结构转换


本研究提出了一种重要且高效的 5,8-二溴-2,11-二叔丁基芫烯 (3) 合成方法，具有多克规模，然后将其转化为一系列新的芫烯芬 (6-10)。使用X射线晶体学研究了具有两个顺式乙烯连接体的管状[2,2](5,8)picenophanediene 8。管到管的反转通过连接体的连续弯曲进行，并且异丙基取代的衍生物10的势垒经实验估计为18.7 kcal/mol。具有大π系统和半刚性结构的Picenophanes表现出异常的光物理性质。乙醇桥联五烯芬表现出弱激子离域，而顺式乙烯桥联五烯芬表现出弱离域激子和准分子的双重发射。借助超快时间分辨发射光谱，解析了准分子形成的机制，显示出具有快速结构变形的两态可逆反应的独特行为，其寿命在298 K时约为20 ps。这项工作表明，桶状五烯芬的桥的微小差异呈现出不同的光物理行为，揭示了利用五烯芬系统中的部分间反应的潜力。