Living on the edge:: A nanographene molecule adsorbed across gold step edges

The unusual adsorption geometry of the large graphene-like polycyclic aromatic hydrocarbon hexa-peri-hexabenzocoronene (HBC) across kinks on the stepped vicinal Au(111212) surface has been studied by synchrotron radiation X-ray photoelectron diffraction (XPD) and scanning tunneling microsco (STM). By a combination of the two techniques a complete characterisation of the adsorption behaviour is achieved, yielding information on preferential adsorption sites (STM) and molecular orientation (XPD). At low coverage (< 0.15 ML) HBC adsorbs across kink sites in fcc-stacking regions with its axis rotated by 19 degrees with respect to the step edge normal direction and the polyaromatic disc tilted by 12 degrees relative to the (111) terraces of the substrate. Furthermore, a small fraction of HBCs adsorbs across straight step edges. The possible exploitation of the characteristic step- and kink-adsorption of molecular derivates of HBC in supramolecular architectures is exemplified at the example of the adsorption of a HBC-derivative on the same substrate. (c) 2008 Elsevier B.V. All rights reserved.