Methyl viologen cation

An interesting aspect of this mechanism is the implicit unreactivity of Z at the electrode, although it reacts with electrogenerated O. This situation has been frequently encountered in the reaction of certain types of biological materials such as heme proteins. An example is the reduction of cytochrome c by electrogenerated methyl viologen cation radical, MV [2] ... 

Lozano MC, Perez RT, Tomas V, et al. 1989. Coulometric determination of organic compounds with methyl viologen cation-radical. Microchem J 39 59-64. 

Scheme 13 Oxygenation of methyl viologen cation radical via radical-radical coupling with O2...

Figure 9. Spectra of cytochrome c (17.5 /tM)-cytochrome c oxidase U2.5 fiM heme a) mixture during reductive indirect coulometric titration using methyl viologen. Titrant increments of 1.04x10" equivalents spectra recorded after each addition of reductive charge. Final two spectra at 605 nm were taken after excess methyl viologen cation radical was present. Adapted from Reference (60) with permission.

Mandler and coworkers have studied the case of twin microdisks (tip and substrate) in which the substrate is unbiased and acts to catalyze the reaction of the product formed at the tip (methyl viologen cation radical) with H+(aq) [83]. This arrangement allows the determination of the substrate potential and exchange current density and was used to analyze the kinetics of proton reduction at the Pt substrate. 

The photochemically excited ( E) state of tra 5-[Cr(cyclam)(NH3)2] can oxidize the methyl viologen cation (MV" ) to give the corresponding Cr(II) macrocycUc complex, but this rapidly loses NH3 in acid solution, and the resulting diaqua complex is oxidized back to Cr(III) with according to... 

The SERS of methyl viologen cations, and MV, and a wide variety of cationic metal complexes have also been observed (Table VIII). With the MV radical cation, both a SERS and a RR process can be observed from the surface Raman spectrum. " The MV and MV cations seem to interact with the Ag surface via adsorbed halides. On adding an electron, the SERS carbon-carbon stretching frequency shifts from 1292 cm for MV to 1352 cm" for MV for the carbons bridging the pyridine rings in the molecule. This upward frequency shift is indicative of increased electron density in the bridging carbon-carbon bond on electron transfer. 

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