Fusing tetrapyrroles to graphene edges by surface-assisted covalent coupling

Surface-assisted covalent linking of precursor molecules enables the fabrication of low-dimensional nanostructures, which include graphene nanoribbons. One approach to building functional multicomponent systems involves the lateral anchoring of organic heteromolecules to graphene. Here we demonstrate the dehydrogenative coupling of single porphines to graphene edges on the same metal substrate as used for graphene synthesis. The covalent linkages are visualized by scanning probe techniques with submolecular resolution, which directly reveals bonding motifs and electronic features. Distinct configurations are identified that can be steered towards entities predominantly fused to graphene edges through two pyrrole rings by thermal annealing. Furthermore, we succeeded in the concomitant metallation of the macrocycle with substrate atoms and the axial ligation of adducts. Such processes combined with graphene-nanostructure synthesis has the potential to create complex materials systems with tunable functionalities.