The charge transfer interaction between methyl viologen (MV+2) and tryptophan (Trp), indole acetic acid (IAA) and indole butyric acid (IBA) was studied in water, in aqueous solutions of sodium dodecyl sulfate (SDS), cetyltrimethylammonium chloride (CTAC) and in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane. The apparent association constants were determined. In the presence of SDS or CTAC the values are of the same order of magnitude as in water, but they depend upon the surfactant concentration. In AOT the values of the equilibrium constant for IAA and Trp are very much higher than in water and they show a strong dependence upon the water/surfactant ratio (R). For IBA the values are much lower, similar to those in water and show practically no variation with R. These effects may be explained by considering the partitioning of the components between the different microphases. Laser flash photolysis of the complex produces the radical cation of methyl viologen in low yield only in the case of CTAC solutions where the process of charge separation is favoured.
indole derivatives; micellar systems
