Keller Tristan J, Sterzenbach Christopher, Bahr Joshua, Schneiders Taria L, Bursch Markus, Kohn Julia, Eder Theresa, Lupton John M, Grimme Stefan, Höger Sigurd, Jester Stefan-S
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 Bering str. 4 53115 Bonn Germany
Chem Sci. 2021 Jun 9;12(27):9352-9358. doi: 10.1039/d1sc01381e. eCollection 2021 Jul 14.
Molecular spoked wheels with and symmetry are synthesized by Vollhardt trimerization of -symmetric dumbbell structures with central acetylene units and subsequent intramolecular ring closure. Scanning tunneling microscopy of the -symmetric species at the solid/liquid interface on graphite reveals triporous chiral honeycomb nanopatterns in which the alkoxy side chains dominate the packing over the carboxylic acid groups, which remain unpaired. In contrast, -symmetric isomers partially allow for pairing of the carboxylic acids, which therefore act as a probe for the reduced alkoxy chain nanopattern stabilization. This observation also reflects the adsorbate substrate symmetry mismatch, which leads to an increase of nanopattern complexity and unexpected templating of alkoxy side chains along the graphite armchair directions. State-of-the-art GFN-FF calculations confirm the overall structure of this packing and attribute the unusual side-chain orientation to a steric constraint in a confined environment. These calculations go far beyond conventional simple space-filling models and are therefore particularly suitable for this special case of molecular packing.
通过具有中心乙炔单元的 - 对称哑铃结构的福尔哈特三聚反应以及随后的分子内环化反应，合成了具有 和 对称性的分子辐条轮。在石墨上的固/液界面处对 - 对称物种进行扫描隧道显微镜观察，发现了三孔手性蜂窝状纳米图案，其中烷氧基侧链在堆积中比未配对的羧酸基团占主导地位。相比之下， - 对称异构体部分允许羧酸配对，因此羧酸可作为降低烷氧基链纳米图案稳定性的探针。这一观察结果还反映了吸附质 - 底物对称性不匹配，这导致纳米图案复杂性增加以及烷氧基侧链沿石墨扶手椅方向出现意外的模板化。最新的GFN - FF计算证实了这种堆积的整体结构，并将不寻常的侧链取向归因于受限环境中的空间位阻约束。这些计算远远超出了传统的简单空间填充模型，因此特别适用于这种分子堆积的特殊情况。
