  A pi-conjugated {C}3h-oligomer involving three dithienylethylene branches
bridged at the meta positions of a central benzenic core has been synthesized
and deposited either on the Si(100) surface or on the HOPG surface. On the
silicon surface, scanning tunneling microscopy allows the observation of
isolated molecules. Conversely, by substituting the thiophene rings of the
oligomers with alkyl chains, a spontaneous ordered film is observed on the HOPG
surface. As the interaction of the oligomers is different with both surfaces,
the utility of the Si(100) surface to characterize individual oligomers prior
to their use into a 2D layer is discussed.
