Molecular organization of bis-urea substituted thiophene derivatives at the liquid/solid interface studied by scanning tunneling microscopy

In this contribution we report on a structural investigation of the two-dim ensional (2D) supramolecular organization of three bis-urea substituted thi ophene derivatives, containing one, two, or three thiophene units, at the s olution/graphite interface with scanning tunneling microscopy (STM); The co mpounds under investigation form highly ordered physisorbed monolayers. It is found that hydrogen bonding between the urea groups of adjacent molecule s controls the spatial arrangement on the graphite surface. Molecular model ing and theoretical calculations demonstrate that the thiophene rings are t ilted with respect to the surface and have partially overlapping pi -system s. This control of the 2D self-assembly is promising for future studies on the electronic properties of these molecules.