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O: Fachverband Oberflächenphysik

O 19: Nanostructures at surfaces: Arrays

O 19.8: Vortrag

Dienstag, 24. März 2009, 12:15–12:30, SCH A215

Towards covalently bonded supramolecular networks - substrate induced polymerisation in 2D — •Hermann Walch, Rico Gutzler, Georg Eder, Wolfgang M. Heckl, and Markus Lackinger — Center for NanoScience (CeNS) und Sekt. Kristallographie, LMU München, Theresienstr. 41, 80333 München

Hydrogen-bonds as stabilizing intermolecular links for supramolecular self-assembly and the influence of the substrate have extensively been investigated. Compared to hydrogen bonded structures, metal-coordination networks were found to be more stable due to increased interaction strength. However, in terms of network stability it is desired to introduce covalent intermolecular bonds. The main challenge is to still maintain ordered growth despite the irreversibility of the bonds. While 3D covalent organic frameworks (COFs) are widely investigated, little is known about surface supported 2D COFs. So far, the preparation of covalently bonded molecular aggregates on surfaces is limited to a few molecules and close-packed structures. Here, we report on the formation of 2D COFs from a halogen substituted polyaromatic compound on Ag(110) and Cu(111) surfaces. Interestingly, on HOPG(001) the same compound forms non-covalently bonded networks which are stabilized by halogen-hydrogen bonds, whereas on metal surfaces the formation of covalent networks is observed. This illustrates that for this compound the substrate is not only an epitaxial template but can also act as a catalyst for the formation of covalent bonds. Experiments were carried out with a Scanning Tunnelling Microscope (STM) at room temperature under ultrahigh vacuum conditions.