Steering Surface Reaction Dynamics with Self-Assembly Strategy

Ullmann coupling of 4-bromobiphenyl thermally catalyzed on Ag(111), Cu(111) and Cu(100) surfaces was scrutinized by scanning tunneling microscopy as well as theoretical calculations. Detailed experimental evidence showed that whether the initially formed organometallic intermediate self-assembled or sparsely dispersed at surfaces essentially determined its subsequent reaction pathways. In specific, the assembled organometallic intermediates at full coverage underwent a single-barrier process to directly convert into the final coupling products while the sparsely dispersed ones at low coverage went through a double-barrier process via newly identified clover-shaped intermediates prior to their formation of the final coupling products. This demonstrates that the self-assembly strategy can efficiently steer surface reaction pathways and dynamics.