Electrochemical NanoScience Group
‹— Nanostructures | ‹— Research topics

2D supramolecular chemistry on surfaces

J.M.Lehn described the supramolecular chemistry as chemistry of the intermolecular bonds, which involves recognition, transformation and translocation of information as key principles. Possible structural motifs of 2D ordering at solid/liquid interfaces are hydrogen bonding, electrostatic interactions, for example dipole and π-stacking, and metal ion-ligand co-ordination. At electrified solid/liquid interfaces, the electrode surface assums the role of an array of charged co-ordination centers of variable geometry and tuneable electron donor and acceptor properties.
In order to test the above concepts we are engaged in model studies with defined substrate/adsorbate systems such as single crystal gold, silver and copper electrodes, and instructed small molecular units (purine and pyrimidine bases, n,n'-bipyridines, substituted terpyridines, hydrogen-bonded template molecules, biphenyles, etc.). Our first goal comprises the direct monitoring of the 2D assembly of the instructed molecules and ions on potentiostatically controlled surfaces with atomic/molecular resolution employing in-situ scanning tunnelling microscopy (STM) and tunnelling spectroscopy (STS). The second goal is focussed on the local addressing and tailoring of molecular properties and functions, specifically conductivity, electron transfer involving individual redox centres and recognition of molecular units.
We hope to demonstrate that the combination of classical electrochemical techniques with in-situ structure-sensitive local probe methods and surface enhanced vibrational spectroscopy (SEIRAS) might open new approaches to explore, under steady state and dynamic conditions, structural and energetic properties of functionalized molecular assemblies and individual molecules at "controlled" solid/liquid interfaces.
Trimesic acid (TMA, 1,3,5-benzene-tricarboxylic acid) represents a prototype system for supramolecular self-assembly. The carboxyl groups of TMA are well-known to form intermolecular hydrogen bonds. This motif is called synthon in crystal engineering and often used as structure-controlling element in molecular fabrication processes. An example is the honeycomb assembly, which is composed of three hydrogen-bonded dimers. The potential to form diverse supramolecular structures makes TMA a unique candidate in 2D self-assembly on surfaces and interfaces.

Revised: 11.12.2007     ©: 2005-2007