Competitive Influence of Hydrogen Bonding and van der Waals Interactions on Self-Assembled Monolayers of Stilbene-Based Carboxylic Acid Derivatives

The molecule–molecule and molecule–substrate interactions play an important role during the formation of two-dimensional (2D) supramolecular nanostructure. In this paper, the self-assembled monolayers of four stilbene derivatives possessing different chemical structures at the liquid–solid interface were investigated by employing scanning tunneling microscopy (STM). Chemical structures that affect the 2D molecular self-assembly, such as number of alkoxyl chain with carboxylic acid end-group and length of alkoxyl chain, were elucidated in detail. Systematic investigation indicated that various self-assembly structures consequently formed on highly oriented pyrolytic graphite (HOPG) surface, via a combination of intermolecular hydrogen bonding and van der Waals interactions. It is proposed that hydrogen bonding and van der Waals interactions competitively control the morphology of the monolayer, and the self-assembled 2D nanostructure is determined by balance of these two interactions