Krämer Philipp, Kohn Julia, Hofmeister David Ari, Kersten Maximilian, Sterzenbach Christopher, Gres Antonia, Hansen Andreas, Jester Stefan-Sven, Grimme Stefan, Höger Sigurd
Kekulé-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany.
Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, Beringstraße 4, 53115, Bonn, Germany.
Angew Chem Int Ed Engl. 2024 Nov 11;63(46):e202411092. doi: 10.1002/anie.202411092. Epub 2024 Oct 2.
A lateral expansion of molecular spoked wheels (MSWs) based on an all-phenylene backbone is described. The MSWs contain a central hub, six spokes, and a rim that is formed by a sixfold Yamamoto coupling of the respective non-cyclized dodecabromo precursor yielding MSWs with up to 30 phenylene rings in the perimeter. Attempts to prepare compounds of such size without flexible side groups at the spokes were unsuccessful, most probably due to an aggregation and accompanying oligomerization of the precursors during the cyclization. To overcome these problems, fluorene units are inserted into the spokes. These contain additional alkyl chains and lead to a curvature of the wheels. Quantum chemical calculations on the mechanism of the Yamamoto coupling lead to geometry and strain-related criteria for the successful rim closure to the respective MSW. Subsequently, MSWs are prepared with four and even six phenylene units at each edge of the hexagonal wheels. The resulting MSWs are characterized by spectroscopic methods, and additionally some of them are visualized via scanning tunneling microscopy (STM).
本文描述了一种基于全亚苯基主链的分子辐条轮（MSW）的横向扩展。MSW包含一个中心轮毂、六条辐条和一个轮辋，该轮辋由各自未环化的十二溴前体通过六重山本偶联形成，得到周长上具有多达30个亚苯基环的MSW。在辐条处没有柔性侧基的情况下制备这种尺寸的化合物的尝试未成功，最可能的原因是环化过程中前体的聚集和伴随的低聚反应。为克服这些问题，芴单元被插入到辐条中。这些芴单元包含额外的烷基链并导致轮的曲率。对山本偶联机理的量子化学计算得出了与几何形状和应变相关的标准，以成功地将轮辋封闭成相应的MSW。随后，在六边形轮的每个边缘制备了具有四个甚至六个亚苯基单元的MSW。所得的MSW通过光谱方法进行表征，此外，其中一些还通过扫描隧道显微镜（STM）进行可视化。
