▎ 摘　　要

On-surface synthesis has been widely used for the precise fabrication of surface-supported covalently bonded nanostructures. Here, we report on tuning the on-surface synthesis of graphene nanoribbons by noncovalent intermolecular interactions on Au(111) surfaces. By introducing noncovalent intermolecular interactions with the companion molecules (dianhydride derivative), intramolecular cyclodehydrogenation of nonplanar precursor molecules (bianthryl derivative) are promoted at 200 degrees C, with the monomers interlinked by gold atoms instead of the formation of polyanthrylene. By adjusting the deposition sequence of precursor and companion molecules, conjugated graphene nanoribbons can be finally obtained at a temperature of 240 degrees C, much lower than the synthesis procedures without companion molecules. Density functional theory calculations indicate that intermolecular interactions result in a dramatic shrinkage of the torsional angle between the adjacent anthryl groups of the precursor molecule, aiding the cyclodehydrogenation process. Our work demonstrates an intermolecular strategy for controllable fabrication of covalently bonded nanostructures by on-surface synthesis.