The morphology of monolayers formed upon adsorption of prochiral 1,5-substituted anthracene derivatives on highly oriented pyrolytic graphite is investigated using scanning tunneling microscopy at the liquid-solid interface. The adsorption orientation of these prochiral anthracene derivatives positions one of their enantiotopic faces in contact with the graphite. The molecules adsorb in rows with contact between adjacent anthracenes. The anthracene side chains extend perpendicular to the direction of the row repeat. All molecules within a single row adsorb via the same enantiotopic face. Anthracenes with side chains containing an even number of non-hydrogenic atoms (C, S) form monolayers in which molecules in adjacent rows adsorb via opposite enantiotopic faces. Anthracenes with side chains that contain an odd number of non-hydrogenic atoms form two-dimensional chiral domains in which all rows contain molecules adsorbed via the same enantiotopic face. This chain length effect on monolayer morphology represents a generalized example of structural effects previously observed in alkanoic acid monolayers formed on HOPG. The variation of the STM current with position in the vicinity of the anthracenes indicates that the highest occupied molecular orbital is the predominant mediator of tunneling for the aromatic group.

The self-assembly of cyanuric acid into ordered nanostructures on a crystalline substrate, highly ordered pyrolytic graphite (HOPG), has been investigated at low temperature under ultrahigh vacuum (UHV) conditions by means of scanning tunneling microscopy in conjunction with theoretical simulations. Many domains with different self-assembly patterns were observed. One such domain represents the formation of an open 2D rosette (cyclic) structure from the self-assembly process, the first observation of this type of structure for pure cyanuric acid on a graphite substrate. Each self-assembled domain exhibits characteristic superstructures formed through different hydrogen bond networks at low coverage and low deposition rate. Experimental observation of coexistent, two-dimensional crystalline structures with distinct hydrogen bond patterns is supported by energy minimizations and molecular dynamics calculations, which show multiple stable structures for this molecule when self-assembled on graphite.