Supramolecular Organization of Model Polycyclic Aromatic Molecules: Comparison of 2D and 3D Assemblies

Abstract

AbstractThe spatial organization of polycyclic aromatic molecules during adhesion on a solid/liquid interface is the key event of a plethora of natural and industrial processes. Herein, we report the supramolecular assembly of violanthrone‐79—a model of asphaltenes, an intractable mixture of polycyclic aromatics from crude oil—at the solid‐liquid interface between highly oriented pyrolytic graphite (HOPG) and a hydrophobic medium (1‐phenyloctane). High‐resolution scanning tunneling microscopy revealed that molecules of violanthrone‐79 readily self‐assemble on the surface in supramolecular “nanoring” structures. The lattice parameters of the 2D unit cell are on the same order as those determined from a bulk single crystal. Transmission electron microscopy showed long‐range ordered patterns, and the spacing between the fringes is in agreement with the inter‐planar distances between aromatic cores of molecules that are helically arranged around the [001] axis in the 3D crystal. The results confirm that upon adsorption on solid/liquid interfaces, polycyclic aromatic molecules such as violanthrone‐79 form supramolecular assemblies by interaction with the substrate and self‐association, and this process could be the initial step of deposition of asphaltenes on carbonaceous oil reservoir walls and production tubing.