Di Giovannantonio Marco, Qiu Zijie, Pignedoli Carlo A, Asako Sobi, Ruffieux Pascal, Müllen Klaus, Narita Akimitsu, Fasel Roman
Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, 8600, Dübendorf, Switzerland.
Istituto di Struttura della Materia - CNR (ISM-CNR), 00133, Roma, Italy.
Nat Commun. 2024 Mar 1;15(1):1910. doi: 10.1038/s41467-024-46173-3.
On-surface synthesis relies on carefully designed molecular precursors that are thermally activated to afford desired, covalently coupled architectures. Here, we study the intramolecular reactions of vinyl groups in a poly-para-phenylene-based model system and provide a comprehensive description of the reaction steps taking place on the Au(111) surface under ultrahigh vacuum conditions. We find that vinyl groups successfully cyclize with the phenylene rings in the ortho positions, forming a dimethyl-dihydroindenofluorene as the repeating unit, which can be further dehydrogenated to a dimethylene-dihydroindenofluorene structure. Interestingly, the obtained polymer can be transformed cleanly into thermodynamically stable polybenzo[k]tetraphene at higher temperature, involving a previously elusive pentagon-to-hexagon transformation via ring opening and rearrangement on a metal surface. Our insights into the reaction cascade unveil fundamental chemical processes involving vinyl groups on surfaces. Because the formation of specific products is highly temperature-dependent, this innovative approach offers a valuable tool for fabricating complex, low-dimensional nanostructures with high precision and yield.
表面合成依赖于经过精心设计的分子前体，这些前体通过热活化来提供所需的共价耦合结构。在此，我们研究了基于聚对亚苯基的模型体系中乙烯基的分子内反应，并全面描述了在超高真空条件下金（111）表面发生的反应步骤。我们发现乙烯基成功地与邻位的亚苯基环环化，形成二甲基二氢茚并芴作为重复单元，该重复单元可进一步脱氢为二亚甲基二氢茚并芴结构。有趣的是，所得聚合物在较高温度下可通过金属表面的开环和重排，由难以捉摸的五边形到六边形转变，从而干净利落地转化为热力学稳定的聚苯并[k]四苯。我们对反应级联的深入了解揭示了涉及表面乙烯基的基本化学过程。由于特定产物的形成高度依赖于温度，这种创新方法为高精度、高产量地制造复杂的低维纳米结构提供了一种有价值的工具。
