Electron Transfer between Phenothiazine and Iron(III) in Micellar Systems [1, 2]

The effect of different surfactant‐forming micelles on the electron transfer reaction between phenothiazine and iron(III), giving rise to phenothiazinium cation radical, has been investigated by means of a stopped‐flow spectrophotometric technique. In cationic and non‐ionic micelles, the reaction rates are strongly decreased, the main paths taking place in the aqueous phase as well as at the water‐micelle interface (this last path has a specific rate constant 2  3 orders of magnitude lower than in homogeneous phase). In anionic micelles, the reaction rate is sharply increased (up to four orders of magnitude in respect to homogeneous phase) reaching a maximum near to the critical micellar concentration. The reaction progresses in micellar phase as well as at micelle‐water interface. The binding constants of phenothiazine with the different surfactants have been estimated.