Highly Selective Cross-Coupling of Asymmetric Dibromonaphthalene Directed by Self-Assembly of Organometallic Intermediates on Ag(111)

Achieving selective cross-coupling of asymmetric precursors is a fundamental challenge in on-surface synthesis due to competing homocoupling reactions. In this study, we demonstrate the coupling reactions of asymmetric 1,7-dibromonaphthalene (1,7-DBN) on Ag(111). The results show that depositing 1,7-DBN on Ag(111) and then annealing at 308 K leads to the formation of symmetric organometallic dimers connected via sites 1 or sites 7. Following annealing at 320 K, asymmetric triangular organometallic trimers connected through sites 1 and 7 are generated, which form large-scale assembled structures on the surface. After further annealing to 390 K, these triangular organometallic trimers transform into triangular covalent trimers linked at sites 1 and 7. The assemblies of triangular organometallic trimers are suggested to act as structural templates that not only suppress molecular desorption but also direct exclusive cross-coupling at sites 1 and 7. This work highlights the significant role of intermediate assemblies in directing the pathway of on-surface reactions. It also establishes molecular assembly as an effective strategy for steering on-surface cross-coupling.