Introducing Design Strategies to Preserve N‐Heterocycles Throughout the On‐Surface Synthesis of Graphene Nanostructures

Despite the impressive advances in the synthesis of atomically precise graphene nanostructures witnessed during the last decade, advancing in compositional complexity faces major challenges. The concept of introducing the desired functional groups or dopants in the molecular precursor often fails due to their lack of stability during the reaction path. Here, a study on the stability of different pyridine and pyrimidine moieties during the on‐surface synthesis of graphene nanoribbons on Au(111) is presented. Combining bond‐resolved scanning tunneling microscopy with X‐ray photoelectron spectroscopy, the thermal evolution of the nitrogen dopants throughout the whole reaction sequence is tracked. A comparative experimental and ab initio electronic characterization confirms the presence of dopants in the final structures, revealing also that the pyridinic nitrogen leads to a significant band downshift. The results demonstrate that, by using synthetic strategies to lower the reaction temperatures, one can preserve specific N‐heterocycles throughout all the reaction steps of the synthesis of graphene nanoribbons and beyond the interibbon coupling reaction that leads to nanoporous graphene. The stability of pyridine and pyrimidine moieties in the process of synthesizing graphene nanoribbons on Au(111) surfaces is studied. Utilizing bond‐resolved scanning tunneling microscopy and X‐ray photoelectron spectroscopy, the thermal behavior of nitrogen dopants throughout the reaction is monitored. The presence of dopants is confirmed by a comparative analysis of the structural and electronic properties with ab initio simulations. Schematic representation of the products obtained by precursors containing different N‐heterocycles.