Transient Spontaneous Raman Study of Photoionization Kinetics at the Hydrocarbon/Water Interface in Micellar Solutions

Article abstract of DOI:10.1021/ja00343a006

Transient spontaneous Raman spectroscopy (416 nm) has been used to observe the kinetics of TMB⁺ and TMB²⁺ ions following photoionization of tetramethylbenzidine (TMB) in aqueous micellar solutions.The ground-state TMB pK_a values are shifted by micellar solubilization in the directions predicted by calculated surface pH values.In SDS micelles, the TMB⁺ ion initially produced is stabilized by negative surface groups.No time evolution of the TMB⁺ Raman spectrum occures, and bimolecular ion reactions are not observed.However, in CTAB micelles, TMB⁺ is destabilized by positive surface groups.The TMB⁺ Raman spectrum evolves on the 10^-6-s time scale, suggesting that the ion has moved into the Stern layer and is assymmetrically solvated.On the 10^-4-s time scale, TMB²⁺ appears from disproportionation of two TMB⁺ ions.Positive spectral identifications are facilitated by comparison with spectra obtained by chemical oxidation in various enviroments.