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This work presents a scanning tunneling microscopy (STM) based study of benzenetribenzoic acid (BTB) monolayer structures at the liquid-solid interface. On graphite(0001) the tailored molecules self-assemble into 2D supramolecular host systems, suitable for the incorporation of other nanoscopic objects. Two crystallographically different BTB structures were found-both hydrogen bonded networks. A specific structure was deliberately selected by solvent identity. One of the BTB polymorphs is a 6-fold chicken-wire structure with circular, approximately 2.8 nm wide cavities. The other structure exhibits an oblique unit cell and a different hydrogen bonding pattern. The large cavity size of the chicken-wire structure was made possible through comparatively strong 2-fold hydrogen bonds between carboxylic groups. In addition, the low conformational flexibility of BTB was supportive to combat the tendency for dense packing.

Stable adsorption of 1,3,5-tris(4-pyridyl)-2,4,6-triazine (TPT) molecules from the liquid phase was only observed in binary solutions, that is, in the presence of a second (adsorptive) species. The process of mediated coadsorption of a molecular species at the liquid−solid interface was accomplished through complexation of TPT with a second type of molecule acting as a “molecular glue” via hydrogen bonds. Scanning tunneling microscopy (STM) was utilized to investigate the structure of the coadsorbed monolayers at the liquid−solid interface. Trimesic acid (TMA) and terephthalic acid (TPA)both benzene rings with disposed carboxylic acid groupswere appropriate to precipitate the stable adsorption of TPT. According to the different symmetry and number of carboxylic acid groups, various networks were observed.

A two-dimensional molecular template structure of 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA) was formed on a highly oriented pyrolytic graphite surface (HOPG) by self-assembly at the liquid-solid interface. Scanning tunneling microscopy (STM) investigations show high-resolution images of the porous structure on the surface. After the host structure was created, coronene molecules were inserted as guest molecules into the pores. STM results indicate that some of the guest molecules rotate inside their molecular bearing. Further investigations show that single coronene molecules can be directly kicked out of their pores by means of STM.

This scanning tunneling microscopy (STM) study uses a supramolecular two-dimensional architecture of trimesic acid molecules adsorbed on a graphite substrate as a host for the incorporation of C60 as a molecular guest. By choosing a proper solvent, it was possible to verify that self-assembly of the host−guest structure can be accomplished at the liquid solid interface. Because of the ideal steric match with the molecular bearing of the host structure, C60 buckminster fullerenes are feasible guests. It was possible to coadsorb C60 within cavities of the open TMA structure from the liquid phase, and lateral manipulation of the molecular guest by the STM tip was demonstrated at room temperature. Because of the increased tip−sample interaction as a result of lower tunneling resistance, a transfer of a C60 molecule from one cavity of the host structure to an adjacent one was achieved.

The adsorption of the aromatic molecule hexabenzobenzene (coronene) on a Ag(111) single crystal surface was investigated under UHV conditions by means of LEED and variable temperature STM. For a very low coverage randomly distributed individual molecules adsorbed on terraces were found. All molecules are surrounded by concentric rings caused by scattering of surface electrons, leading to the formation of standing waves. These surface electrons mediate an additional intermolecular interaction with an oscillatory potential in the distance between molecules. The balance of all forces leads to a typical spacing of 2.4 nm for isolated molecular dimers. For monolayer coverage, a long-range ordered close packed structure was found. Calibration of the coronene LEED pattern with the substrate spots provided the superstructure unit cell parameters. These were used for distortion correction and a subsequent correlation analysis, which improves the quality of the submolecular resolved images. The zoom shows a tilt of...

The adsorption of 1,3,5-Benzenetricarboxylic (Trimesic) Acid (TMA) to a single crystal graphite surface has been studied under Ultra High Vacuum conditions. This work focuses on inducing a particular self-assembly structure by OMBE (Organic Molecular Beam Epitaxy), characterized by periodic non-dense-packing of the molecules. Two coexisting phases could be imaged with sub-molecular resolution by STM. Induced by directed hydrogen bonding, the organic molecules built in both cases a two-dimensional grid architecture with molecular caves. This two-dimensional host structure can accept single trimesic acid guest molecules in different positions.

In this paper, we report on a new method for the investigation and manipulation of single molecules by STM without the explicit need for experimentally challenging UHV techniques. The controlled manipulation of single molecules becomes possible, since an organic template preadsorbed on the substrate introduces a hexagonal grid of stable adsorption sites with a next nearest neighbor distance of approximately 1.6 nm.

The adsorption of the aromatic molecule hexabenzobenzene (coronene) on an HOPG(0001) surface was investigated under UHV conditions by means of variable temperature scanning tunneling microscopy (STM) and spectroscopy (STS). Imaging on a mesoscopic scale showed a distribution of coronene islands. These islands are mobile on the surface and can be pinned at step-edges. Zooming in on areas apart from the islands reveals an hexagonal arrangement of coronene molecules in a closed layer. Submolecular resolved molecules consist of bright spots with varying intensity. This variation in intensity is explained with the commensurability of the adlayer. STS investigations were performed for various tip-sample distances, adjusted by the tunneling current setpoint. A gap can be seen for every setpoint, but its width is dependent on the setpoint. The gap for the largest tip-sample distance and therefore the smallest tip-sample interaction is compared with the theoretical value.