Electrochemistry, supramolecular assembly

Although, from a purely chemical point of view, learning how to create these complicated supramolecular structures has its own value, there are plenty of more practical reasons to investigate this chemistry. In the short term, these include catalysis and sensor applications, and in the long term, molecular electronics and molecular machines. With perhaps the exception of catalysis, all these applications will require some sort of signal transduction to allow for communication with the supramolecular device. This, of course, is one of the main reasons that electrochemistry is useful for supramolecular chemistry. Electron transfer provides a well-understood and very sensitive method to both communicate with supramolecular assemblies and control their structure.8... 

Modern surface analytical tools make it possible to probe the physical structure as well as the chemical composition and reactivity of interfacial supramolecular assemblies with unprecedented precision and sensitivity. Therefore, Chapter 3 discusses the modern instrumental techniques used to probe the structure and reactivity of interfacial supramolecular assemblies. The discussion here is focused on techniques traditionally applied to the interrogation of interfaces, such as electrochemistry and scanning electron microscopy, as well as various microprobe techniques. In addition, some less common techniques, which will make an increasing contribution to supramolecular interfacial chemistry over the coming years, are considered. 

A. E. Kaieer, M. Gomez-Kaieer, In Supramolecular Electrochemistry Self-Assembled Monolayers WUey-VCH Weinheim, 1999, 91-206. 

Electrochemical investigations are found in the areas of molecular electronics and nanotechnology. Electrochemistry can be used to produce and characterize clean surfaces (e.g., electrochemical cleaning of metals). It can direct the assembly and structure of supramolecular assemblies (e.g., by using self-assembled or spontaneously adsorbed... 

With regard to its electronic properties, no studies are available that clearly demonstrate that electron transfer through such a supramolecular assembly is possible. Solid-state electrochemical studies on the crystalline material are not available at the present time. The closest to supramolecular electrochemistry are studies of ordered two-dimensional peptide arrays on gold. For some Fc-peptide cystamines, self-assembled monolayers of Fc-peptide cystamines were prepared that allow the quantification of the electron transfer kinetics by electrochemical techniques. Similar to the supramolecular assemblies, H-bonding plays an important role. At the present time (2003), only a few systems were studied and offer a rather complex picture of the ET properties. Additional experimental work is required to obtain definite results on the influence of the peptide primary and secondary structure on ET kinetics. In addition, tile issue of lateral interactions needs to be addressed by detailed dilution studies with alkylthiols. 

Like the currently popular area, called nanoscience , the field of supramolecular chemistry has rather hazy boundaries. Indeed, both areas now share much common ground in terms of the types of systems that are considered. From the beginning, electrochemistry, which provides a powerful complement to spectroscopic techniques, has played an important role in characterizing such systems and this very useful book goes considerably beyond the volume on this same topic by Kaifer and Gomez-Kaifer that was published about 10 years ago. Some of the classic supramolecular chemistry topics such as rotaxanes, catenanes, host-guest interactions, dendrimers, and self-assembled monolayers remain, but now with important extensions into the realms of fullerenes, carbon nanotubes, and biomolecules, like DNA. 

R.L. is grateful for the Marie Curie Fellowship of the European Community program Improving Human Research Potential Socio-Economic Knowledge Base, contract number HPMF-CT-2000-00804. H.J. and D.J.F. also acknowledge the support by the Ecole Polytechnique Federale de Lausanne and the Fonds Nationale Suisse de la Recherche Scientifique (Project 20-55692.98). The Laboratories of Electrochemistry of the University of Liverpool and EPFL are part of the European TMR network SUSANA (Supramolecular Self-Assembly of Interfacial Nanostructures). 

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