On-surface cyclization of vinyl groups on poly-para-phenylene involving an unusual pentagon to hexagon transformation

On-surface synthesis relies on carefully designed molecular precursors that are thermally activated to afford desired, covalently coupled architectures. In a recent publication, we studied the reactions of vinyl groups on poly-para-phenylene and provided a comprehensive description of all 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. This record contains the data that support the scientific results in the publication.

表面合成（On-surface synthesis）依赖于精心设计的分子前驱体，此类前驱体经热活化后可得到目标共价偶联结构。在近期一项研究中，我们针对聚对亚苯基（poly-para-phenylene）表面的乙烯基（vinyl groups）反应展开了系统探究，并对超高真空条件下Au(111)表面发生的所有反应步骤进行了全面表征。我们发现，乙烯基可与邻位亚苯基环顺利发生环化反应，生成以二甲基二氢茚并芴（dimethyl-dihydroindenofluorene）为重复单元的结构，该单元可进一步脱氢得到二亚甲基二氢茚并芴（dimethylene-dihydroindenofluorene）结构。值得注意的是，所得聚合物在更高温度下可完全转化为热力学稳定的苯并[k]并四苯（polybenzo[k]tetraphene），该过程涉及此前鲜有报道的、通过金属表面开环重排实现的五边形-六边形结构转变。我们对该反应级联过程的深入解析，揭示了表面乙烯基参与的基础化学过程。由于特定产物的生成对温度具有高度依赖性，该创新策略为高精度、高产率制备复杂低维纳米结构提供了极具价值的研究手段。本数据集包含支撑该论文中科学结论的全部实验数据。