Although helicenes are promising molecules, the synthetic difficulty and tediousness have often been problems, and only small amounts of optically pure helicenes have been obtained by using chiral HPLC in most cases. Herein, aza[7]helicenes or closed‐aza[7]helicenes with (1R)‐menthyl substituents were selectively synthesized via the intramolecular Scholl reaction, and the diastereomeric pairs were separated by silica gel column chromatography. The optically pure helicenes were further transformed into the corresponding cyclic dimers, and the chiroptical properties were investigated. The rigid p‐frameworks of the dimers led to the high molar extinction coefficients and fluorescence quantum yields, while the twisted helicene moieties induced clear Cotton effects and CPL in the visible region, and the high CPL brightness (BCPL) was achieved. Furthermore, the cyclic dimers were found to have the macrocyclic cavity with the two NH groups suitable for the selective binding of a fluoride anion, which induced significantly redshifted fluorescence and CPL in the red region.

中文翻译：

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环状氮杂氮杂环二聚体表现出明亮的圆偏振发光和选择性氟化物识别


尽管螺旋烯是一种很有前途的分子，但合成困难和繁琐往往是个问题，并且大多数情况下使用手性高效液相色谱法只能获得少量光学纯的螺旋烯。在此，通过分子内Scholl反应选择性合成了氮杂[7]螺旋烯或带有(1R)-薄荷基取代基的封闭氮杂[7]螺旋烯，并通过硅胶柱色谱分离了非对映体对。将光学纯的螺旋烯进一步转化为相应的环状二聚体，并研究其手性光学性质。二聚体的刚性p-骨架导致了高摩尔消光系数和荧光量子产率，而扭曲的螺旋烯部分则在可见光区域诱导了明显的Cotton效应和CPL，并实现了高CPL亮度（BCPL）。此外，发现环状二聚体具有带有两个NH基团的大环空腔，适合氟阴离子的选择性结合，从而在红色区域诱导显着红移的荧光和CPL。