Supramolecular Corrals on Surfaces Resulting from Aromatic Interactions of Nonplanar Triazoles

Abstract

Interaction forces between aromatic moieties, often referred to as π-π interactions, are an important element in stabilizing complex supramolecular structures. For supramolecular self-assembly occurring on surfaces, where aromatic moieties are typically forced to adsorb coplanar with the surface, the possible role of intermolecular aromatic interactions is much less explored. Here, we report on unusual, ring-shaped supramolecular corral surface structures resulting from adsorption of a molecule with nonplanar structure, allowing for intermolecular aromatic interactions. The discrete corral structures are observed using high-resolution scanning tunneling microscopy, and the energetic driving forces for their formation are elucidated using density functional theory calculations and Monte Carlo simulations. The individual corrals involve between 11 and 18 molecules bound through triazole moieties to a ring-shaped ensemble of bridge site positions on (111) surfaces of copper, silver, or gold. The curvature required to form the corrals is identified to result from the angle dependence of aromatic interactions between molecular phenanthrene moieties. The study provides detailed quantitative insights into triazole-surface and aromatic interactions and illustrates how they may be used to drive surface supramolecular self-assembly.

Scanning Tunneling Microscopy Investigation of Two-Dimensional Polymorphism of Structural Isomers

“…In addition, it could be possible that molecules within a phthalimide tetramer are not planar on the surface and could be stabilized by π–π stacking interactions. Although π–π interactions are weak interactions, there are 2D assemblies that have been formed by the π–π stacking interactions. , Although lower in energy than hydrogen bonding, the π–π stacking interactions have been shown to compete with the hydrogen bonding interactions to drive the formation of self-assembled architectures …”

Effect of the pH in the growth of benzotriazole model layers at realistic environmental conditions

“…For example, they have been shown to produce unexpected 2D structures, like supramolecular corrals, on which the closest separation between the observed features is calculated as 3.2 Å for dimer pairs [80], and 3D Kagome-like lattices, where π-π stacked molecular dimers adsorb perpendicularly over a layer of flatlying molecules [81].…”

Revealing the Limits of Intermolecular Interactions: Molecular Rings of Ferrocene Derivatives on Graphite Surface

“…We presume a similar scenario for the previously reported molecular rings/spirals. , Thus, it is summarized that molecular rings formed by predominantly weak intermolecular interactions should always possess a limiting inner/outer diameter and should be independent of size, shape, and chemical nature of the molecules. We also note that the molecular rings with a very small inner diameter (∼4 nm) are possible if the formation of rings is assisted by a strong molecule–substrate interaction. , …”

“…We also note that the molecular rings with a very small inner diameter (∼4 nm) are possible if the formation of rings is assisted by a strong molecule−substrate interaction. 16,18 We observe the formation of discrete molecular rings/spirals of two small ferrocene derivatives on graphite. The molecular rings show a limiting value of the inner and outer diameters, which closely correlates with those of molecular rings of a few other molecules on graphite.…”

“…Molecular rings/spirals have been shown for alkyl-substituted tetrathiafulvalene and long-chain carboxylic acids on a HOPG surface. However, strong molecule–substrate (metallic) interactions − and templates like gas bubbles − have shown to trigger the formation of molecular rings on different surfaces. The spontaneously formed discrete molecular rings reported so far are based on large molecules with high structural flexibility.…”