Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
Instituto de Química, Centro de Tecnologia, Universidade Federal do Rio de Janeiro, 21941-909 Rio de Janeiro, Rio de Janeiro, Brazil.
J Am Chem Soc. 2022 Dec 7;144(48):22316-22324. doi: 10.1021/jacs.2c10865. Epub 2022 Nov 20.
The intrinsic relationship between helicenes and circulenes is of fundamental interest and importance in molecular engineering. Herein, electrophilic borylation of phenanthroline-derived aza[5]helicenes is presented, resulting in the incorporation of a boryl unit into two termini of helicenes to afford quasi-[7]circulenes. Their bowl-shaped structures were determined by X-ray diffraction. UV-vis absorption and fluorescence spectroscopy, as well as electrochemical measurements and DFT calculations, gave insight into their electronic properties. Variable-temperature NMR studies and DFT calculations revealed bowl-to-bowl inversion at room temperature and bowl-to-helix equilibria at elevated temperature, highlighting the important role of B ← N bond strength in tuning their dynamic properties.
螺旋芳烃和轮烷芳烃之间的内在关系在分子工程中具有基础的兴趣和重要性。在此，展示了源于菲咯啉的氮杂[5]螺旋芳烃的亲电硼化反应，该反应将硼基单元引入螺旋芳烃的两个末端，得到准[7]轮烷芳烃。通过 X 射线衍射确定了它们的碗状结构。紫外-可见吸收光谱、荧光光谱以及电化学测量和 DFT 计算深入研究了它们的电子性质。变温 NMR 研究和 DFT 计算揭示了在室温下的碗-碗翻转和在高温下的碗-螺旋平衡，突出了 B←N 键强度在调节它们的动态性质方面的重要作用。
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