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 transconformer 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.
Pyridine derivatives R 0380Practical Routes to 2,6-Disubstituted Pyridine Derivatives. -The regioselective functionalization of the pyridine core becomes possible with the BuLi-DMAE superbase for selective α-lithiation followed by a Grignard reaction. The route is applied to prepare pyridines bearing an aryl group in the 6-position and an alkyl group in the 2-position. The pyridines are studied for their self-assembly abilities at the interface between an organic solution and the basal plane of graphite. -(VANDROMME, L.; REISSIG*, H.-U.; GROEPER, S.; RABE, J. P.; Eur.
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