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Several geminal bis-urea compounds were synthesised by means of an acid-catalysed condensation of various benzaldehydes with different monoalkylureas. Many of these compounds form thermoreversible gels with a number of organic solvents at very low concentrations (< 3 mm) and which are stable to temperatures higher than 100 8C. Electron microscopy revealed a three-dimensional (3D) network of intertwined fibres, which are several tens of micrometers long and have a width ranging from approximately 30 to 300 nm. The possible aggregate forms and aggregate symmetries were evaluated by means of molecular mechanics calculations. 1 H NMR, 2D NMR, 13 C NMR and 13 C-CP/MAS NMR techniques were used to obtain information about the aggregation and possible aggregate symmetry of geminal bis-ureas in solution, in the gel state, and in the solid state.

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. In this contribution we report on a structural investigation of the two-dimensional (2D) supramolecular organization of three bis-urea substituted thiophene derivatives, containing one, two, or three thiophene units, at the solution/graphite interface with scanning tunneling microscopy (STM). The compounds under investigation form highly ordered physisorbed monolayers. It is found that hydrogen bonding between the urea groups of adjacent molecules controls the spatial arrangement on the graphite surface. Molecular modeling and theoretical calculations demonstrate that the thiophene rings are tilted with respect to the surface and have partially overlapping π-systems. This control of the 2D self-assembly is promising for future studies on the electronic properties of these molecules.

In this contribution we investigated the two-dimensional (2D) supramolecular organization and electronic properties of two bis(urea)-substituted oligothiophene derivatives, containing two or three thiophene units (T2 and T3, respectively), at the solution/graphite interface with scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Because of the π-stacking of the oligomers the observed zero conductance band gap in the I(V) curves of a ribbon is found to be considerably smaller than for an isolated oligothiophene molecule, indicating that there exists an effective conjugation in the π-stacked ribbons on the surface.