Chirale polyzyklische aromatische Kohlenwasserstoffe mit Affensattel-Topologie [Data]

In this thesis, the first chiral polycyclic aromatic hydrocarbon (PAH) with a monkey saddle topology is presented. Starting from a truxene building block that is readily preparatively accessible, the monkey saddle PAH could easily be obtained in three steps. By using additional functionalized precursors, a series of twelve derivatives has been obtained and characterized. Solid-state structures confirmed the three-dimensional shape of the PAHs unambiguously, which is induced by the five-, six- and eight-membered rings. This makes the PAH a section of a Mackay-type crystal. Due to the curvature, the target compounds exhibit triple axial chirality. Separation of the enantiomers was possible and characterization of these via CD spectroscopy and the investigation of racemization revealed half-lives ranging from a few milliseconds to several days. In addition, first attempts to synthesize Mackay-like cage compounds have been conducted and provided important insights for future projects. A deeper insight into the properties of the curved PAHs was achieved by the isosteric exchange of three CH groups with nitrogen. Its effect could be studied in detail and led to a stabilization of the enantiomers towards a half-life of two months. Furthermore, a rearrangement was developed that lead to a chiral molecular basket whose enantiomers do not longer racemize at room temperature. The experimental results were supported and extended by a large number of quantumchemical calculations. A second truxene precursor formed the basis on which the preparation of a system with three azulene units succeeded. Synthetic difficulties on the way to the target compound could be circumvented and thus a keto-functionalized PAH has been obtained, which forms two separable diastereomers. The azulene PAH represents a model of a graphene defect due to the five- and seven-membered rings and was studied in terms of its photophysical and electrochemical properties as well as compared with isomeric compounds. Confirmation of the structures of all three target compounds by X-ray structural analysis was also successful. First experiments on post-functionalization were performed so that future projects can build on them.

本论文首次报道了具有猴鞍状拓扑结构的手性多环芳烃（polycyclic aromatic hydrocarbon, PAH）。以易于制备的曲星烯（truxene）砌块为起始原料，仅需三步反应即可便捷合成该猴鞍状PAH。通过引入额外的功能化前驱体，我们成功合成并表征了共计12种衍生物。固态结构分析明确证实了该类PAH的三维空间构型，该构型由五元环、六元环与八元环共同诱导形成，因此该PAH可作为麦凯型（Mackay-type）晶体的结构片段。由于分子存在固有曲率，目标化合物具有三重轴向手性。我们成功实现了其对映异构体（enantiomers）的分离，并通过圆二色（Circular Dichroism, CD）光谱对其进行表征，同时对外消旋化过程开展研究，结果显示其半衰期范围为数毫秒至数天不等。此外，我们首次尝试合成类麦凯笼状化合物，相关研究为后续项目提供了重要参考。通过将三个CH基团进行氮原子等排置换，我们进一步深入探究了这类曲面PAH的性质，详细研究了该置换的作用效果，发现其可显著稳定对映异构体，使其半衰期延长至两个月。此外，我们开发了一种重排反应，得到一种手性分子篮，其对映异构体在室温下不再发生外消旋化。大量量子化学计算辅助并拓展了上述实验结果。以第二种曲星烯（truxene）前驱体为基础，我们成功制备了含有三个薁（azulene）单元的体系。我们克服了目标化合物合成过程中的诸多难题，得到一种酮基功能化的PAH，该化合物可形成两种可分离的非对映异构体。由于含有五元环与七元环，该薁基PAH可作为石墨烯缺陷的模型分子，我们对其光物理与电化学性质开展了研究，并与同分异构体进行了对比分析。通过X射线结构分析，我们成功确认了全部三种目标化合物的结构。我们还开展了首例后功能化（post-functionalization）实验，为后续研究奠定了坚实基础。