The Influence of Sodium Dodecyl Sulfate on the Photoionization of the Ruthenium(tris)bipyridine Dication

Abstract

Abstract Using single-pulse and two-pulse two-colour laser flash photolysis (308 nm and 355 nm), we have quantitatively studied the effect of sodium dodecyl sulfate (SDS), at concentrations above and below the critical micellar concentration (cmc), on the cyclic photoionization of the ruthenium(tris)bipyridine dication in aqueous medium. In contrast to reports in the literature (Chem. Phys. Lett. 315 (1999) 416) about a superincrease of the electron yield by SDS concentrations in the range between 3.0 · 10 –4 M and 4.5 · 10 –4 M we found that the observed absorption increases are entirely due to background signals in the vicinity of an insolubility range, as can be proved by difference experiments (argon-saturated vs. N2O-saturated solutions); SDS has no appreciable effect on the reaction below the cmc, and causes a moderately increased electron yield above the cmc. By varying the excitation intensities and analyzing the intensity dependences, we have shown that that increase is not due to a facilitation of the photoionization proper by the micelles but to a more efficient photoreduction of the oxidized complex by SDS in that cyclic mechanism.