Electron-transfer reactions in SDS micelles: Reactivity of pyrene and tris(2,2 '-bipyridyl)ruthenium(II) excited states investigated by time-resolvedluminescence quenching

The effects of micellization on the rate constants and Gibbs energy of elec tron transfer (Delta G(et)) are studied by time-resolved luminescence quenc hing of tris(2,2'-bipyridyl)ruthenium(II) (RUBIPY) and pyrene (FY) by elect ron accepters and donors in sodium dodecylsulfate (SDS) micelles. For RUBIF Y, which is bound to the SDS micelles and accessible to water, Delta G(et) is considerably smaller than what is found in organic solutions, though the spectral properties of RUBIFY and the value of diffusion-controlled quench ing rate constant are typical for the micellar interior. For this system, d issolution in micelles enables a change of the local reactant concentration and mobility, retaining their higher reactivity in aqueous solution. In co ntrast, for PY, which is known to be localized in the palisade layer of an SDS micelle, the quenching rate constants coincide well with those found in acetonitrile.