The effect of multiple pairs of meta-dicarboxyl groups on molecular self-assembly and the selective adsorption of coronene by hydrogen bonding and van der Waals forces

The prediction of two-dimensional molecular self-assembly structures has always been a problem to be solved. The molecules with meta-dicarboxyl groups can self-assemble into a specific hexagonal cavity, which has an important influence on the prediction of molecular self-assembly structures and the application of functional molecules with meta-dicarboxyl groups. Two kinds of molecules with four pairs of meta-dicarboxyl groups, 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene (H₈TIAPy) and 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1’-biphenyl]-3,5-dicarboxylic acid)) (H₈ETTB) molecules were chosen to observe the self-assembly behavior at the heptanoic acid/highly oriented pyrolytic graphite (HA/HOPG) interface. H₈TIAPy molecules self-assembled into well-ordered quadrilateral structures and could be regulated into kagomé networks with hexagonal pores by coronene (COR) molecules. H₈ETTB molecules self-assembled into lamellar structures and transformed into acid-COR-acid-COR co-assembled structures at low concentration of COR solution and acid-COR dimer-acid-COR dimer co-assembled structures at high concentration of COR solution. The reason that H₈ETTB molecules could not be regulated into hexagonal porous architecture was attributed to the steric hindrance by the similar length and width of H₈ETTB molecules. The H₈ETTB templates had stronger adsorption for COR than that of hexaphenylbenzene (HPB), regardless of the order of molecular introduction.