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）是一种构建功能结晶聚合物材料的颇具前景的方法，然而，与溶液中发生的各种反应相比，关于SSTP反应的报道却极为有限。狄尔斯-阿尔德反应（DA）以及脱氢狄尔斯-阿尔德反应（DDA）是制备溶液中六元环的经典反应，但在固态合成中却鲜有出现。在本研究中，我们运用多种尖端技术，证明了固态1,4-二苯基丁二炔（DPB）在10-20 GPa的压力下发生DDA反应，其中苯基作为共轭二烯体。在临界压力下的晶体结构表明，该反应具有“距离选择性”。苯基与苯乙炔基之间的3.2 Å距离促进了DDA反应，而其他DDA和1,4-加成反应的距离则过大，无法形成键合。所得产物为结晶的扶手椅石墨烯纳米带，因此，我们的研究开辟了一条构建具有原子级控制的结晶碳材料的新途径。