Electronic single cyclic voltammetric wave

A simple estimate of electronic coupling can be obtained from studies employing cyclic voltammetry [37], If two M2 centers are strongly coupled, then oxidation of the electronically coupled centers will lead to two successive waves that are well separated. If the two centers were connected by a perfect insulator, that is, no electronic coupling, then each M2 center would undergo oxidation at the same potential and the single cyclic voltammetric wave on oxidation would correspond to a two-electron process. 

Details of the electrochemical reduction of 36 and the possible existence of the monoanionic intermediate (36) (R = Ph) are not yet settled. The neutral dimer is reported to undergo a single, chemically reversible, two-electron reduction at a mercury electrode (E = -1.26 V in CH3CN) (79), although the process was less reversible (R = Ph or Me) in propylene carbonate (81) and totally irreversible at platinum (79). The peak separation of 45 mV (at mercury), which contrasts with the expected value of 30 mV for a reversible two-electron reduction, is reported to be essentially independent of the cyclic voltammetric scan rate (79). Although this seems to imply that the overall process may consist of two closely spaced one-electron waves, mixing solutions of [36] (R = Ph) and 36 (R = Ph) did not produce a sufficient concentration for [36] (R = Ph) to be detected by ESR spectroscopy. Thus, the high disproportionation constant for the reaction ... 

Consider the special case of an E Eq reaction, where the first electron transfer is fast (nernstian) and the second somewhat slower. The cyclic voltammetric behavior, such as for AE = 0 as shown in Figure 12.3.28, depends upon the scan rate. At smaller scan rates (curve A), a single wave with behavior approaching the case, is seen. As the scan rate is increased (i.e., as A2 decreases), the first electron-transfer wave remains reversible and centered on E, but the slower second electron transfer results in a... 

Fleischmann and Pletcher have reported the cyclic voltammetric data for a series of aromatic hydrocarbons in the AlClg-NaCl-KCl (50-36-14 mole %) melt. Large polynuclear hydrocarbons showed several electron transfers, while simple hydrocarbons showed a single wave. The electrode reactions were found to be almost reversible. Jones et who obtained... 

Cyclic and pulsed voltammetric studies of Mb-surfac-tant films have been used to obtain electrochemical parameters such as electron transfer rate constants and formal potentials E° ), i.e. apparent standard potentials under given experimental conditions. Recent work has shown that a Gaussian distribution model for protein molecules with slightly different ° -values fits voltammetric data in thin surfactant films [26, 33]. This model was used with nonlinear regression to extract average ° and values from square wave voltammograms (SWV). Simple models for voltammetry of single species confined to the electrode surface did not fit the data, but formal potentials could be estimated from the midpoints of CV cathodic and anodic peaks. 

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