Temperature-Directed Hierarchical Surface Supramolecular Assembly

Abstract

The hierarchical organization of building blocks is an important characteristic of self-assembly. Herein, we report a series of triangular hierarchical assemblies formed by C3-symmetric 5,10,15-triethyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole-2,7,12-tricarbaldehyde (M1) on the graphite surface. The molecule assembles into a hexagonal array on the graphite surface at room temperature with a trimeric assembly motif as the basic building block of the hierarchical assembly. With the increase of annealing temperature, the sizes of triangles in hierarchical assemblies vary from large to small with the presence of antiparallelly arranged molecular dimers as building blocks at the triangular boundaries. The hierarchical-order-level-dependent intermolecular interaction and molecule–substrate interaction were modeled, and the entropy contributions of alkyl substitution at different temperatures were proposed to account for the observed structural evolution process. This work provides a new example of hier...