Overview of current research.

The principal objective of research in this group is the elucidation of the mechanisms of complex, multi-step electrode reactions of organic and organometallic compounds. The results of this research are relevant not only in the areas of organic and inorganic chemistry, but also find applications in chemical analysis, electroorganic synthesis, pollution control, electrocatalysis, batteries and fuels cells.

A full understanding of an electrode reactions must include a complete description of its component steps. Thus, our work includes studies of the factors controlling the rates of simple electron-transfer reactions occurring at electrode surfaces as well as the electron-transfer reactions in solution near the electrode that involve the various species in the overall mechanism (reactants, intermediates, products).

Other component reactions are of a more chemical nature. They may be as simple as an isomerization or conformational change of the reactant or an intermediate. However, bonds may also be formed (dimerization, protonation) or broken (loss of an atom or functional group) and these steps combine with the electron-transfer reactions to make up the overall process.

An important type of reaction is bond cleavage associated with electron transfer to or from the reactant. Most such reactions are two-step processes in which an intermediate radical anion is formed followed by expulsion of a leaving group. However, others appear to be concerted processes (dissociative electron-transfer reactions) in which both steps occur together and no intermediate radical ion exists. Part of our research is directed toward discovering new examples of the rarer type, dissociative electron transfers.

The techniques that are employed include all of the methods of electroanalytical chemistry with particular emphasis on the use of microelectrodes to facilitate fast measurements. The group is especially well known for the application of fast scan cyclic voltammetry to electroanalytical problems. New capabilities recently acquired include instrumentation for electrochemical impedance spectroscopy and the electrochemical quartz crystal microbalance. The standard chromatographic and spectroscopic methods are employed for the characterization of the starting materials and products of electrode reactions.

Systems to be studied are selected principally on the basis of their relevance to practical problems. Examples include studies of hexaarylbiimidazoles which are components of commercial imaging systems, determination of the redox properties of N-F fluorinating reagents that are widely used for mild and selective fluorination, and studies of the mechanisms of electrode reactions that are used for synthetic purposes in the hope of improving the efficiency and selectivity of electroorganic synthesis. Of course, other systems are studied simply because they are interesting. An example of such an area is our long term interest in subtle structural changes (conformational change or isomerizaton) associated with electron transfer and this research continues to provide exciting new results.

 Members of the Evans research group.

Curriculum vitae- Dennis Evans

Recent Publications from the Evans group.

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