On-surface synthesis of N-doped zig-zag nanochains

On-surface synthesis offers unprecedented atomic-level control in fabricating N-doped zig-zag nanostructures with tailored π-conjugation and a spin-polarized edge state, laying the foundation for the design and synthesis of organic quantum materials with tailored spin and charge transport properties. Herein, we systematically investigate the substrate-regulated self-assembly and thermal-induced reaction pathways of DAQ-Br molecules on Ag(111) and Au(111) surfaces using STM, achieving atomic-scale visualization of structural evolution from molecular self-assembly to zig-zag nanochains. Distinct coverage-dependent assembly patterns stabilized by different Br-based interactions are formed on Ag(111) and Au(111) surfaces. Thermal annealing triggers diverse pathways: on Ag(111), C-Ag-C organometallic chains are predominantly formed, with limited generation of C-C coupling products, whereas on Au(111), well-ordered zig-zag C-C covalent chains are directly formed. The zig-zag covalent nanochains obtained on the Au(111) surface exhibit a higher yield and a better long-range order. Furthermore, DFT calculations unravel the underlying differences in assembly behaviors and covalent coupling efficiencies on both surfaces. This study provides fundamental insights into the rational design of precursors for synthesizing target N-doped zig-zag nanostructures with controlled topologies by on-surface synthesis.