Emergent Chirality from Pairing of Achiral Molecules: Homochiral Chains of Paired 1,10‐Phenanthroline on Au(111)

ABSTRACT Understanding how chirality emerges from assemblies of achiral molecules is central to the study of symmetry breaking at surfaces. Here we show that achiral 1,10‐phenanthroline adsorbed on Au(111) generates chirality through a pairing‐driven hierarchical self‐assembly pathway. Upon adsorption, molecules selectively form hydrogen‐bonded pairs via weak but directional C─H···N interactions. Steric and electrostatic constraints restrict this interaction to two molecules, forcing a choice between two symmetry‐equivalent nitrogen sites and thereby producing left‐ or right‐handed molecular pairs that act as local chiral motifs. These motifs organize through attractive intermolecular interactions into homochiral one‐dimensional chains, which further assemble into two‐dimensional chiral domains governed by repulsive interchain interactions. Scanning tunneling microscopy directly visualizes mirror‐related left‐ and right‐handed domains. Density functional theory calculations confirm that the face‐to‐face paired configuration is energetically preferred and stabilized by adsorption on Au(111). This work reveals a distinct route to surface chirality in which chirality originates at the level of a hydrogen‐bonded molecular pair and is amplified into organized chiral architectures through weak intermolecular interactions.