Hydrodynamic effect in diffusion-controlled reaction

Deutch, J. M.; Felderhof, B. U.

doi:10.1063/1.1680247

Cited by 109 publications

(110 citation statements)

References 4 publications

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“…Theoretical analyses have predicted that the hydrodynamic effects, the effects of the solvent structures, or both slow the relative diffusion of solutes at short solute-solute distances in molecular liquids. [44][45][46] More recently, Tavernier et al investigated photoinduced bimolecular electron transfer reactions by fluorescence spectroscopy. 47 In this report as well, solute diffusion was found to be restricted by the hydrodynamic effects and the effects of the solvent structures at short solute-solute distances.…”

Section: Scheme 1: Schematic Representation Of the Model Used For Slementioning

confidence: 99%

Magnetic Field Effect on a Radical Pair Reaction as a Probe of Microviscosity

2008

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The magnetic field effects (MFEs), caused by the ∆g mechanism, on the photoinduced hydrogen abstraction reaction of benzopheneone with thiophenol were investigated in alcoholic solutions of varying viscosities (η ) 0.55 to 59.2 cP) by a nanosecond laser flash photolysis technique. The escape yield of benzophenone ketyl radicals (Y) gradually decreased with increasing magnetic field strength (B) from 0 to 1.6 T. The relative yield observed at 1.6 T, R(1.6 T) ) Y(1.6 T)/Y(0 T), decreased with increasing η in the range of 0.55 cP e η e 5 cP, and then increased with increasing η in the range of 5 cP < η e 55.3 cP. When η was higher than 55.3 cP, the R(1.6 T) value became 1.0, and MFEs were completely quenched. The observed η dependence of the MFEs was analyzed by the stochastic Liouville equation (SLE), in which the effects of spin-orbit coupling by a heavy atom such as sulfur were taken into account. The observed MFEs were reproduced fairly well by the SLE analysis. The diffusion coefficients of the radicals obtained by the SLE were about three times smaller than those expected from the macroscopic solvent viscosities. One can probe the microviscosity in the vicinity of the radical pairs by observing MFEs on the present photochemical reaction system. IntroductionMagnetic field effects (MFEs) on photochemical reactions through radical pairs (RPs) and biradicals have received considerable attention during the past three decades. 1-3 Magnetic fields interact with the electron spins of RPs, and thus the spin conversion in the RPs is influenced by the fields. The lifetime of the RPs and the yield of the escaped radicals consequently show appreciable MFEs. In solution, the MFEs on the reactions of RPs have been interpreted in terms of the radical pair and triplet mechanisms (RPM and TM, respectively). According to the RPM, MFEs are observed during sequential steps as follows:(1) formation of close RPs through photochemical reactions with singlet (S) or triplet (T n , n ) 0, (1) spin multiplicity, (2) spin conversion between S and T n states in separated RPs, and (3) spin state selective recombination of the close RPs competing with the escape of radicals from the pairs. 2 These steps are promoted by the diffusion of the radicals by which the RPs are separated and re-encountered. Radical diffusion, therefore, has a pronounced effect on the magnitude of the observed MFEs. Large MFEs have been observed in confined and inhomogeneous systems such as micellar solutions, 2,3 highly viscous solutions, 4,5 nanotubes, 6 and very recently ionic liquids. 7 Molecular and radical diffusions are important processes that control chemical reactions in solutions. 8 Radical diffusion motion has been studied with the several techniques, including transient grating (TG), 9 photochemical space intermittency, 10,11 and electron paramagnetic resonance (EPR). 12,13 These techniques provide valuable information on radical diffusion in homogeneous solutions. Using the TG technique, for example, Terazima et al. found that photochemically genera...

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Section: Scheme 1: Schematic Representation Of the Model Used For Slementioning

confidence: 99%

Magnetic Field Effect on a Radical Pair Reaction as a Probe of Microviscosity

2008

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“…The hydrodynamic effect can slow diffusion near contact by a factor of 4 compared to bulk diffusion. 52,53 Because most electron transfer occurs near contact, the radial distribution function and the hydrodynamic effect can have a significant influence on the time dependence of intermolecular electron transfer in a given system. 2,3,5,51 In this paper, experimental data are presented for electron transfer between octadecylrhodamine B (ODRB) and either N,Ndimethylaniline (DMA) or N,N-dimethyl-1-naphthylamine (DMNA) in three types of aqueous micelle solutions: dodecyl-, tetradecyl-, and cetyltrimethylammonium bromide (DTAB, TTAB, and CTAB, respectively).…”

Section: Introductionmentioning

confidence: 99%

“…The rate of diffusion is distance-dependent as described by the hydrodynamic effect. [52][53][54] The distance dependence of diffusion is brought into the electron transfer theory through D(r), the distance-dependent diffusion parameter. 51 The consequence of the hydrodynamic effect is slower diffusion at short donoracceptor distances.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Intermolecular Electron Transfer in Micelles: Dielectric and Structural Properties of Micelle Headgroup Regions

2001

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Photoinduced intermolecular (donor/acceptor) electron transfer is studied both experimentally and theoretically for donors and acceptors located in the headgroup region of micelles. Fluorescence up-conversion and fluorescence yield measurements were performed to characterize photoinduced electron transfer from N,Ndimethylaniline (DMA) and N,N-dimethyl-1-naphthylamine (DMNA) to octadecylrhodamine B (ODRB) in three types of aqueous micelle solutions: dodecyl-, tetradecyl-, and cetyltrimethylammonium bromide (DTAB, TTAB, and CTAB, respectively). The data were analyzed with a detailed theory that assumes a Marcus distance-dependent rate constant. Because DMA, DMNA, and ODRB reside in the headgroup region of the micelles, the theory includes diffusion of the molecules in this region of the micelles. The micelles are modeled as a spherical core of low dielectric constant surrounded by a spherical shell headgroup region with intermediate dielectric properties, which in turn is surrounded by water. An analytical theory, which accounts for geometrical and dielectric properties of the three-region micelle environment, is used to calculate the solvent reorganization energy and free energy of transfer. To fit the data, the three-region dielectric model is necessary, and the dielectric constant of the micelle headgroup region of each micelle can be approximately determined. In addition, including local structure is required to fit the data, yielding some information about molecular organization in the headgroup region.

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“…33, the actual rate k, can be up to 607, srna!ler than that caicillated through [12] ~f the hydrodynamic effects are included in the theory. The h e a r approxirnat~on form of this theory gives the result (33) Can.…”

Section: Ana!ysis Of K Vrlluesmentioning

confidence: 99%

Acid dissociation constants and rates as studied by ultrasonic absorption

Green¹,

Kruus²,

McGuire³

1976

Can. J. Chem.

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Experimental ultrasonic absorption data on solutions of H2SO4 and H3PO4 are interpreted in terms of proton transfer equilibria. The acid dissociation constants obtained are compared with those obtained using other methods and are shown to be consistently lower. A model is proposed to explain this in terms of ΔVθ and ΔHθ involved in the steps leading to recombination of the proton with the anion. This model is supported by the values of the reaction distance parameters calculated from the value of the rate constant obtained for the recombination rate. The accuracy of this rate constant is dependent on the accuracy of the ΔVθ value used for the equilibrium. Experimental density data are presented here as an aid in determining ΔVθ. Problems involving activity coefficients in such solutions are discussed in the course of checking the values used for species present in sulfuric acid solutions.

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Hydrodynamic effect in diffusion-controlled reaction

Cited by 109 publications

References 4 publications

Magnetic Field Effect on a Radical Pair Reaction as a Probe of Microviscosity

Magnetic Field Effect on a Radical Pair Reaction as a Probe of Microviscosity

Photoinduced Intermolecular Electron Transfer in Micelles: Dielectric and Structural Properties of Micelle Headgroup Regions

Acid dissociation constants and rates as studied by ultrasonic absorption

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