Zhang Chi, Kazuma Emiko, Kim Yousoo
Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Angew Chem Int Ed Engl. 2019 Dec 2;58(49):17736-17744. doi: 10.1002/anie.201909111. Epub 2019 Oct 23.
Dehalogenative cycloaddition reaction is a powerful strategy to generate new ring scaffolds with π-conjugated features on a surface, and thus holds great promise toward atomically precise electronic devices or nanomaterials. The ortho-dihalo substitution provides a good strategy to realize cycloaddition. However, the limited understanding of intermediate states involved hinders mechanistic exploration for further precise design and optimization of reaction products. Now, the evolutions of competing surface-stabilized radicals and organometallic intermediates in real space were visualized toward the formation of dominant conjugated four-membered ring connections. From the interplay of scanning tunneling microscopy and density functional theory calculations, the stepwise metal-mediated dehalogenative cycloaddition pathway is elucidated both experimentally and theoretically. The results provide fundamental insights into the intermediate states involved in on-surface synthesis.
脱卤环加成反应是一种在表面生成具有π共轭特征的新型环骨架的有效策略，因此在原子精确的电子器件或纳米材料方面具有巨大潜力。邻二卤代取代为实现环加成提供了一种良好的策略。然而，对所涉及的中间态的有限理解阻碍了对反应产物进行进一步精确设计和优化的机理探索。现在，在实空间中竞争的表面稳定自由基和有机金属中间体向形成占主导地位的共轭四元环连接的演化过程得以可视化。通过扫描隧道显微镜和密度泛函理论计算的相互作用，从实验和理论上阐明了逐步的金属介导脱卤环加成途径。这些结果为表面合成中涉及的中间态提供了基本见解。
