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

Abstract

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.