Ordering of Molecules with π-Conjugated Triangular Core by Switching Hydrogen Bonding and van der Waals Interactions

Using alkoxylated derivatives of triangular dehydrobenzo[12]annulene (DBA) as building blocks, we demonstrate control of a formation of 2D molecular networks on Au(111). The tunability of intermolecular interactions by substituting alkoxy groups can improve the homogeneity of the 2D molecular network by restricting the number of polymorphs, and it can induce domain-specific chirality. The 7 pi-conjugated triangular core of each alkoxylated DBA derivative is locked on a specific site on the Au(111) surface by the interaction between the oxygen atoms of the molecule and the gold (Au) surface atoms, and the relative importance of intermolecular hydrogen bonding versus van der Waals interactions depends on the length of the alkoxy groups. Such tunable intermolecular interactions balanced with surface-molecule interaction may eventually enable control of the formation of 2D molecular networks. These results could lead to potential applications in tailoring 2D molecular networks or allow the use of these networks as templates. The 2D molecular networks are investigated using scanning tunneling microscopy, and modeling is based on density functional theory calculations.