The reductive electrochemistry of methylviologen was surveyed in the presence of sodium dodecyl sulfate (SDS), Triton X-100, and cetyltrimethylammonium bromide (CTAB) micelles. The half-wave potentials of the MV2+/MV+· and MV+·/MV couples were found to be dependent on the medium composition. The conproportionation constant for the reaction MV2+ + MV ⇌ MV+· decreases in the order SDS micelles > H2O > Triton X-100 micelles > CTAB micelles. Electron spin resonance of these solutions demonstrated that the electron exchange rate between the dication and the cation radical is reduced in the presence of SDS micelles but is unaffected by cationic or nonionic micelles, compared to the micelle-free solution. Absorption spectra showed that the equilibrium constant for dimerization of the cation radical is depressed by the SDS micelles, suggesting that MV+· resides in an essentially nonaqueous environment, such as the micelle hydrocarbon core. Detection of the critical micelle concentration of SDS solutions is possible through the changes observed in the shape of the cyclic voltammograms.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry