Spectroelectrochemistry methods, reversible

The chemical stability and electrochemical reversibility of PVF films makes them potentially useful in a variety of applications. These include electrocatalysis of organic reductions [20] and oxidations [21], sensors [22], secondary batteries [23], electrochemical diodes [24] and non-aqueous reference electrodes [25]. These same characteristics also make PVF attractive as a model system for mechanistic studies. Classical electrochemical methods, such as voltammetry [26-28] chronoamperometry [26], chronopotentiometry [27], and electrochemical impedance [29], and in situ methods, such as spectroelectrochemistry [30], the SECM [26] and the EQCM [31-38] have been employed to this end. Of particular relevance here are the insights they have provided on anion exchange [31, 32], permselectivity [32, 33] and the kinetics of ion and solvent transfer [34-... 

The OTTLE method is very useful for slow electron transfer kinetics such as those of biological redox processes, in which a mediator is frequently used in an indirect coulometric titration [6, 36] and metal complexes with slow heterogeneous kinetics. An example of the latter is a copper complex in which the Cu(II/I) couple very often shows a broad quasi-reversible wave due to slow heterogeneous kinetics. In this case, spectroelectrochemistry is a useful method for obtaining accurate E° values [37]. 

One of the most powerful methods of evaluating the properties of mixed-valence complexes is spectroelectrochemistry. A key experiment is to reversibly cycle a dinuclear complex through fully oxidized, mixed-valence and fully reduced states. A near IR absorption band that appears only in the electronic spectrum of the mixed-valence state is strong evidence for an intervalence transition. Determination of the nature of the mixed-valence state can also be achieved by spectroelectrochemical methods. 

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