On-Surface Synthesis of Azapolyarenes and Their Bromine-Assisted Chiral Self-Assembly

The rational design of molecular precursors that direct divergent surface reactions offers powerful opportunities for controlling the formation and organization of heteroatom-doped π-conjugated nanostructures. Here, we report the on-surface synthesis of three distinct azapolyaromatic compounds─a helicene, a pyrazine, and a nanographene─obtained from a single brominated precursor on Au(111). Thermal activation triggers selective dehalogenation, C-C or C-N coupling, and intramolecular cyclodehydrogenation, giving rise to structurally defined products whose structures were elucidated by scanning tunneling microscopy and density functional theory calculations. Remarkably, the resulting species undergo bromine-assisted self-assembly into phase-separated two-dimensional domains, reflecting differences in molecular chirality, planarity, and intermolecular interactions. These findings highlight the potential of programmed on-surface chemistry for generating multiple heteroatom-doped aromatic architectures from a single feedstock, providing a versatile strategy for the atomically precise construction of functional nanographenes and chiral π-systems.