Weak hydrogen bonds as a structural motif for two-dimensional assemblies of oligopyridines on highly oriented pyrolytic graphite: an STM investigation

We present the STM investigation of four different oligopyridines at the liquid/highly oriented pyrolytic graphite interface. The heteroaromatic compounds are constitutional isomers showing the same overall shape regardless of their actual conformation. On the basis of weak intermolecular C-H...N hydrogen-bonding interactions, different nanopatterns are formed following a simple general concept for the two dimensional self-assembly. The molecules arrange either in linear or in cyclic structures. Though the oligopyridines are achiral, the formation of prochiral trimeric superstructures leads to chiral phases due to the immobilization on the surface. Some of the molecules show polymorphic structures depending on the solvent. The large variety of the presented structures formed by self-assembly of the different oligopyridines which retain the same functional heteroaromatic backbone shall open the possibility of exploiting these patterns as templates for the nanostructuring of surfaces with guests such as small molecules or metal ions for intriguing applications in, for example, catalysis.