Critical Role of Phenyl Substitution and Catalytic Substrate in the Surface-Assisted Polymerization of Dibromobianthracene Derivatives

Understanding the nature and hierarchy of on-surface reactions is a major challenge for designing coordination and covalent nanostructures by means of multistep synthetic routes. In particular, intermediates and final products are hard to predict since the reaction paths and their activation windows depend on the choice of both the molecular precursor design and the substrate. Here, we report a systematic study of the effect of the catalytic metal surface to reveal how a single precursor can give rise to very distinct polymers that range from coordination and covalent nonplanar polymer chains of distinct chirality to atomically precise graphene nanoribbons and nanoporous graphene. Our precursor consists on adding two phenyl substituents to 10,10′-dibromo-9,9′-bianthracene, a well-studied precursor in the on-surface synthesis of graphene nanoribbons. The critical role of the monomer design in the reaction paths is inferred from the fact that the phenyl substitution leads to very distinct products in each one of the studied metallic substrates.