Contrasting Behaviors of 2,7‐Dibromotriphenylene on Ag(110) and Au(110): From Self‐Assembly to Oriented Covalent Polymerization

ABSTRACT

The on‐surface reactions of 2,7‐dibromotriphenylene (DBTP) on Ag(110) and Au(110) surfaces have been systematically investigated by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. On Ag(110), DBTP molecules form self‐assembled structures upon mild annealing, and both the molecules and bromine atoms desorb at 385 K without covalent coupling. In contrast, on the reconstructed Au(110) surface, DBTP molecules undergo dehalogenative homocoupling upon thermal activation, leading to the formation of highly oriented polymer chains aligned along the direction. We identify the thermally induced transition from physisorbed lying‐down configurations to chemisorbed standing‐up geometries as the key factor enabling this directional growth. This study highlights the critical role of substrate topography and reactivity in governing molecular adsorption and steering on‐surface polymerization pathways.