Concentration and Coverage Dependent Adlayer Structures: From Two-Dimensional Networks to Rotation in a Bearing

Abstract

A bisterpyridine based molecule, 3,3′-BTP, shows a variety of adlayer structures at the interface between highly oriented pyrolytic graphite (HOPG) and the liquid depending on the concentration in solution. Three closely related linear and one hexagonal 2D patterns are found. Comparison with the self-assembly at the HOPG|gas interface shows that in the absence of the solvent one of the linear and the hexagonal structures can be found. The concentration dependent order of appearance of the different surface structures is rationalized by a thermodynamic model. In the adlayer unit cell, the hexagonal phase offers a central void which is mostly filled with a seventh 3,3′-BTP molecule. In the presence of the solvent, those molecules are presumably rotating, whereas at the HOPG|gas interface no clear rotation can be observed.

Supramolecular Approaches to Graphene: From Self‐Assembly to Molecule‐Assisted Liquid‐Phase Exfoliation

“…This behavior of 3,3′-BTP molecules is in stark contrast to that observed on HOPG, wherein well-ordered 2D patterns were monitored. [148] On EG/Ru(0001) the molecules exclusively occupied the 'valley' sites while most of the bright 'hill' sites remained vacant. This observation was found to be in good accordance with theoreti cal calculations, which revealed the difference in adsorption energy between 'valley' and 'hill' sites as high as ≈ 0.36 eV.…”

Principles of molecular assemblies leading to molecular nanostructures

“…Careful control over concentration can aid in selecting a specific structure, especially when two or more polymorphs are possible that differ in packing density or adsorption energy [30][31][32][33][34][35]. One of the first examples of concentration-dependent self-assembly was discovered in the case of alkoxylated DBA derivatives [30].…”

Adsorption of Supramolecular Building Blocks on Graphite: A Force Field and Density Functional Theory Study

“…The strong interaction here is just a consequence of the large size of the molecule, leading to the dominant contribution of the van der Waals interaction to the bonding, which keeps the molecule adsorbed on the surface up to temperatures above 500 K. [15] Furthermore, because of the nondirectional nature of the van der Waals interaction, the adsorption energy of BTP on graphite exhibits only a small corrugation, that is, it depends very weakly on the lateral position of the molecule. Hence, the particular arrangement of BTP molecules in an ordered supramolecular structure on graphite [2,27] is almost entirely determined by the formation of intermolecular hydrogen bonds. [11] In order to trace back the reason for the large discrepancy between force field calculations and experiment, we used the optimized geometry obtained from each force field for singlepoint DFT-D2 [6] energy calculations, that is, without any further structure optimization.…”