Electron-Transfer Reactions in SDS Micelles:  Reactivity of Pyrene and Tris(2,2‘-bipyridyl)ruthenium(II) Excited States Investigated by Time-Resolved Luminescence Quenching

Soboleva,; Stam, Jan van; Dutt, G. B.; Kuz'min, M.G.; Schryver, FC De

doi:10.1021/la981452g

Cited by 17 publications

(9 citation statements)

References 68 publications

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“…The minimal effect is in line with literature data for electron-transfer reactions between excited SDS-bound ruthenium tris(2,2′-bipyridyl) and a series of micelle-solubilized quenchers for which the rate constants and energetics are similar to those in aqueous solution. 6 By contrast, electron-transfer quenching of the excited state of an aqueous ruthenium complex by diheptyl viologen bound to SDS micelles is over an order of magnitude slower than the same reaction in aqueous solution. 7 The present results indicate that radical cations provide excellent probes for studying electron-transfer reactivity in anionic micelles.…”

Section: Discussionmentioning

confidence: 99%

Electron-Transfer Reactions in Micelles: Dynamics of Psoralen and Coumarin Radical Cations

et al. 2001

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Radical cations of several psoralens and coumarins have been generated by photoionization in aqueous micellar solution for a comparison of their dynamic behavior with results observed previously in aqueous solution. The photoionization efficiencies are significantly higher in anionic sodium dodecyl sulfate (SDS) micelles than in aqueous solution as a result of favorable electrostatic effects that lead to rapid ejection of the electron into the aqueous phase. By contrast, much lower quantum yields are measured in neutral and cationic micelles. Experiments with anionic quenchers that are soluble only in the aqueous phase demonstrate that exit of the radical cations from anionic SDS micelles is too slow to measure (<105 s-1) under our conditions. Exit rate constants from neutral Triton X-100 micelles are approximately an order of magnitude faster. Comparison of equilibrium constants for both triplet and radical cations of 4,5‘,8-trimethylpsoralen demonstrates that electrostatic effects lead to an order of magnitude enhancement of the affinity of the radical cation for the anionic vs neutral micelles, as compared to the triplet of the same substrate. The slow exit of the radical cation from the micelle facilitates the measurement of rate constants for reaction of the micelle-incorporated radical cations with both water soluble quenchers and species for which exchange between micelle and aqueous phases is rapid on the time scale of the radical cation lifetime. This work provides some of the first kinetic data for dynamics of exit of reactive radical cations from micelles and indicates that these species may provide useful probes for studying electron-transfer dynamics in micellar media.

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Section: Discussionmentioning

confidence: 99%

Electron-Transfer Reactions in Micelles: Dynamics of Psoralen and Coumarin Radical Cations

et al. 2001

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“…48 -50 Comparing the values inside micelles 18,40,90 and in bulk acetonitrile solution, 92 one can expect that the k d values in the former can be only of the order of ϳ5ϫ10 8 dm 3 mol Ϫ1 s Ϫ1 ͑assuming ϳ10 cP), much lower than the maximum k q values observed for the present systems. In fact, in the work of Soboleva et al, 93 a k d value for SDS micellar solution is estimated to be ϳ3 ϫ10 8 dm 3 mol Ϫ1 s Ϫ1 . Present results thus indicate that the mutual diffusion of the reactants might not play any significant role in determining the quenching kinetics for the present systems.…”

Section: Correlation Of the Quenching Constants With The Free-enermentioning

confidence: 99%

Photoinduced intermolecular electron transfer from aromatic amines to coumarin dyes in sodium dodecyl sulphate micellar solutions

Kumbhakar

Nath

Pal

et al. 2003

The Journal of Chemical Physics

184

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Photoinduced intermolecular electron transfer interaction between coumarin dyes and aromatic amines has been investigated in sodium dodecyl sulphate micellar solutions using steady-state and time-resolved fluorescence quenching measurements. Steady-state fluorescence quenching of the coumarin dyes by the amine quenchers always shows a positive deviation from linear Stern-Volmer relationship, which arises due to the localized high quencher concentrations at the micellar Stern layer. In time-resolved fluorescence measurements, the analysis of the fluorescence decays following a micellar quenching kinetics model assuming a unified quenching constant (k q Ј) per quencher occupancy does not give satisfactory results, especially for the higher quencher concentrations used. The observed fluorescence decays are, however, seen to fit reasonably well following a bi-exponential analysis for all the quencher concentrations used. The average fluorescence lifetimes of the coumarin dyes in the micellar solution as estimated from the bi-exponential decay analysis are seen to undergo a systematic reduction with the effective mean quencher concentrations. The bimolecular quenching constants (k q ) thus estimated are seen to be much smaller than those reported in the homogeneous solutions ͑e.g., in acetonitrile͒, indicating that the electron transfer in the micellar media is inherently inefficient. Correlation of the observed k q values in the micellar solutions with the free-energy changes (⌬G 0 ) for electron transfer reactions show an inversion in the observed rates as predicted by Marcus' outer sphere electron transfer theory at exergonicities more that ϳ0.65 eV. To the best of our knowledge this is the first report on the Marcus inverted region observed for the electron transfer reactions in micellar solution.

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“…There are several accounts regarding the physical nature and excited‐state dynamics of [Ru(bpy) 3 ] 2+ in premicellar (12) and micellar (17–24) SDS. In aqueous solution, equimolar mixtures of [Ru(bpy) 3 ] 2+ and SDS precipitate, presumably as the [Ru(bpy) 3 ] dodecyl sulfate salt (23).…”

Section: Resultsmentioning

confidence: 99%

Lengthening of Fluorescence Lifetimes in Self-organized Metal-Organic Assemblies ¶

Luman

Castellano

2007

Photochemistry and Photobiology

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Resonance energy transfer from tris(2,29-bipyridyl)ruthenium (II) ([Ru(bpy) 3 ] 2+ ) to nile blue A is demonstrated in aqueous solution in the presence of sodium dodecyl sulfate (SDS). At SDS concentrations below the critical micelle concentration, aggregates that permit energy transfer between these dyes at optically dilute (10 lM) concentrations with nearly 100% efficiency are formed. The disparity between the lifetimes of the donor and acceptor results in the lengthening of the photoluminescence lifetime of the sensitized emission observed from nile blue A. Time-resolved luminescence measurements confirm that the long-lived components of the emission originate from sensitized acceptor emission.

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Electron-Transfer Reactions in SDS Micelles: Reactivity of Pyrene and Tris(2,2‘-bipyridyl)ruthenium(II) Excited States Investigated by Time-Resolved Luminescence Quenching

Cited by 17 publications

References 68 publications

Electron-Transfer Reactions in Micelles: Dynamics of Psoralen and Coumarin Radical Cations

Electron-Transfer Reactions in Micelles: Dynamics of Psoralen and Coumarin Radical Cations

Photoinduced intermolecular electron transfer from aromatic amines to coumarin dyes in sodium dodecyl sulphate micellar solutions

Lengthening of Fluorescence Lifetimes in Self-organized Metal-Organic Assemblies ¶

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