Spectro-Electrochemical Toolbox: Techniques to Unravel Redox Reaction Mechanisms

Electrochemical processes represent a major class of chemical reactions in the laboratory as well as in industrial applications. Analytical electrochemistry continues to be an excellent method to yield energy data in the form of redox potentials, to determine concentrations, and to elucidate formal reaction mechanisms through kinetic analysis. However, alone, is not able to characterize unknown species that are formed as intermediates or as products in a redox reaction. The combination of electrochemistry with species-focused spectroscopy, commonly known as spectroelectrochemistry (SEC), can solve this problem and thus allow for a more complete analysis of electron-transfer processes and complex redox reactions. This semi-tutorial presentation will provide the audience with an insight into a variety of SEC techniques including UV-Vis-NIR, IR, EPR and NMR-spectroelectrochemistry. The advantages, drawbacks and potential limitations of each method, particularly with respect to in-situ or online applications, will be discussed. Examples from the STU lab will be used to illustrate the power of the combination tools from the SEC toolbox in the understanding of the redox chemistry of fullerenes, organic push-pull super-acceptors, non-innocent ligand organometallic complexes as well as supramolecular devices.  Finally, as a small detour, few advanced pulsed EPR and ENDOR methods extending the SEC analysis will be introduced.