ELECTRON-TRANSFER REACTIONS BETWEEN VIOLOGEN RADICAL CATIONS AND QUINONES IN AOT REVERSE MICELLES STUDIED BY ELECTRON PULSE-RADIOLYSIS

Electron-transfer reactions between viologen radical cations (CnV•+, n = 1-18) and various quinones have been studied in aqueous and reverse micellar (AOT/isooctane/H2O) solution by use of the electron pulse radiolysis technique. The quinones were either water- or oil-soluble exclusively while the viologens showed a distribution equilibrium between water pool and surfactant interface. By use of dynamic light scattering measurements, the concentration of water pools was determined and the number of electron-transfer reactants per water pool could be calculated. Rate constants measured for the reaction between CvV•+ radicals and anthraquinonesulfonate ions (AQS-) decreased with increasing length of the aliphatic chain of the viologens, caused by association of the viologen with the surfactant interface. Viologens with chain length n ≥ 12 did not show any electron transfer to AQS- ions. None of the viologen radicals (n = 1-18) reacted with oil-soluble quinones (dimethylnaphthoquinone, vitamin K1). The data gave information about the solubilization site of the reactants as well as about the orientation of the CnV molecules in the surfactant interface. © 1990 American Chemical Society.