Optical switching studies of an azobenzene rigidly linked to a hexa-peri-hexabenzocoronene derivative in solution and at a solid-liquid interface

Abstract

An azobenzene moiety rigidly linked to a hexa-peri-hexabenzocoronene (HBC) derivative has been switched optically between its trans- and cis-conformations in solution. Crystalline monolayers of the flat lying trans-conformer have been obtained at the interface between the basal plane of graphite and an organic solution. However, from the illuminated solution no cis-conformer was observed adsorbed to the interface, indicating that the resulting cis- conformer is not thermodynamically stable at this interface, possibly due to the competition with the coexisting trans-conformers. Therefore, two-dimensional honeycombs self-assembled from derivatives of three-fold symmetric polycyclic aromatic hydrocarbons were investigated, which may be employed as templates, providing the necessary space for conformational switching of an azobenzene moiety, and tune the current-voltage characteristics through the aromatic cores. As a first step towards this goal, the capability of the template to host single molecular guests was studied by filling the voids with individual coronene molecules.