Bottom-Up Fabrication of Graphene Nanoribbons with Nonalternant 5/7/5 Ring Motifs

Nonbenzenoid carbon nanostructures have attracted increasing attention because of their unique electronic, magnetic, and optoelectronic properties. However, their precise synthesis has remained challenging for both conventional solutions and on-surface synthetic approaches. In this work, we demonstrate the successful fabrication of graphene nanoribbons (GNRs) incorporating 5/7/5 ring motifs on Au(111) via surface-assisted Wurtz couplings followed by cyclodehydrogenation of a dibromomethyl-substituted aromatic molecule. The resulting GNRs exhibit two distinct symmetry types arising from the trans- and cis-configurations of the precursor during coupling, with their atomistic structures unambiguously characterized by noncontact atomic force microscopy. Through combined scanning tunneling spectroscopy investigations and density functional theory simulations, we elucidate the distinct electronic structures and aromatic characteristics of these nanoribbons. This study establishes a novel synthetic strategy for constructing 5/7/5 ring-containing GNRs, offering valuable insights for precursor design and reaction pathway control for low-dimensional nonbenzenoid carbon nanomaterials.