Identification of a peripheral substitution symmetry effect in self-assembled architectures

Two complementary classes of molecules based on a triphenylene core are synthesized. The two-dimensional (2D) assemblies of these molecules deposited on a highly oriented pyrolytic graphite (HOPG) surface are identified with scanning tunneling microscopy (STM). Structures with large cavities are formed by symmetric molecules, while uniform and closely packed stripe-assembled structures are obtained for asymmetric molecules. X-ray diffraction (XRD) results support the observation of an ordered hexagonal columnar mesophase for symmetric molecules and a rectangular columnar mesophase for asymmetric molecules. The study demonstrates that the substitution symmetry has significant effects on the assembly characteristics of molecular architectures and also on the three-dimensional (3D) macroscopic properties of the molecular materials.