Distance-Selected Topochemical Dehydro-Diels–Alder Reaction of 1,4-Diphenylbutadiyne toward Crystalline Graphitic Nanoribbons

Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric materials, but in contrast to various reactions that happen in solution, only very limited types of SSTP reactions are reported. Diels-Alder (DA) and dehydro-DA (DDA) reactions are textbook reactions for preparing six-membered rings in solution but are scarcely seen in solid-state synthesis. Here, using multiple cutting-edge techniques, we demonstrate that the solid 1,4-diphenylbutadiyne (DPB) undergoes a DDA reaction under 10-20 GPa with the phenyl as the dienophile. The crystal structure at the critical pressure shows that this reaction is distance-selected. The distance of 3.2 Å between the phenyl and the phenylethynyl facilitates the DDA reaction, while the distances for other DDA and 1,4-addition reactions are too large to allow the bonding. The obtained products are crystalline armchair graphitic nanoribbons, and hence our studies open a new route to construct the crystalline carbon materials with atomic-scale control.

固态拓扑化学聚合（SSTP）是构建功能性结晶聚合物材料的一种有前景的方法，但与溶液中发生的各种反应相比，报道的SSTP反应类型非常有限。狄尔斯 - 阿尔德（DA）反应和脱氢 - 狄尔斯 - 阿尔德（DDA）反应是在溶液中制备六元环的经典反应，但在固态合成中很少见。在此，我们利用多种前沿技术证明，固态的1,4 - 二苯基丁二炔（DPB）在10 - 20吉帕压力下以苯作为亲双烯体发生DDA反应。临界压力下的晶体结构表明该反应是距离选择性的。苯与苯乙炔基之间3.2 Å的距离促进了DDA反应，而其他DDA反应和1,4 - 加成反应的距离过大，无法成键。所获得的产物是结晶的扶手椅型石墨纳米带，因此我们的研究开辟了一条在原子尺度上控制构建结晶碳材料的新途径。