Chiral Hierarchical Molecular Nanostructures on Two-Dimensional Surface by Controllable Trinary Self-Assembly

The bottom-up fabrication of surface hierarchical nanostructures is of great importance for the development of molecular nanostructures for chiral molecular recognition and enantioselective catalysis. Herein, we report the construction of a series of 2D chiral hierarchical structures by trinary molecular self-assembly with copper phthalocyanine (CuPc), 2,3,7,8,12,13-hexahexyloxy-truxenone (TrO23), and 1,3,S-tris(10-carboxydecyloxy) benzene (TCDB). A series of flower-like chiral hierarchical molecular architectures with increased generations are formed, and the details of these structures are investigated by high resolution scanning tunneling microscopy (STM). The flower-like hierarchical molecular architectures could be described by a unified configuration in which the lobe of each architecture is composed of a different number of triangular shape building units (TBUs). The off-axis edge-to-edge packing of TBUs confers the organizational chirality of the hierarchical assemblies. On the other hand, the TBUs can tile the surface in a vertex-sharing configuration, resulting in the expansion of chiral unit cells, which thereby further modulate the periodicity of chiral voids in the multilevel hierarchical assemblies. The formation of desired hierarchical structures could be controlled through tuning the molar ratio of each component in liquid phase. The results are significant for the design and fabrication of multicomponent chiral hierarchical molecular nanostructures.