Electron-Transfer Quenching of the Luminescent State of the Tris(bipyridyl)ruthenium(II) Complex in Micellar Media

Article abstract of DOI:10.1021/j100458a019

Observations of the orange luminescence from the excited state of Ru(bpy)3(2+) ions have been used to follow the photoredox reaction between this species and methyl (and other N-alkyl) viologen ions dispersed in aqueous and micellar media.Time-resolved experiments show that the luminescence decays in an exponential manner both in water and in micellar media composed of the surfactant sodium dodecyl sulfate even under conditions where the quencher distribution about micelles should require nonexponential behavior.The rate constants in H2O clearly showed a kinetic salt effect.The effect of viologen concentration could be interpreted in terms of the quenching process occurring within the diffuse double layer of the micelles.This was supported by observations of the decay of the photoredox products using kinetic absorption spectrophotometry.In reverse micelles formed from Aerosol OT in heptane or cyclohexane, exponential decay of the luminescence was only observed at low methyl viologen concentrations.At concentrations above ca. 2 mM (varied with water content) double exponential behavior was observed.With duroquinone as quencher in the reverse micellar system, quenching occurred but no indication of the ionic products of the photoredox process was found.This indicates that duroquinone partitions into the aqueous pool of the reverse micelles and no phase transfer of electrons or product ions is occurring.