Quantum effects of high-frequency modes in inorganic electron transfer: kinetic isotope effects in redox reactions of hexaaquairon(2+) ion ([Fe(H2O)6]2+, hexa(aqua-d2)iron(2+) ion ([Fe(D2O)6]2+), and hexa(aqua-18O)iron(2+) ion ([Fe(18OH2)6]2+)

Guarr, Thomas F.; Buhks, Ephraim; McLendon, George

doi:10.1021/ja00350a002

Cited by 36 publications

(43 citation statements)

References 2 publications

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“…Since on isotopic substitution the dipole moment and the polarizability of the solvent molecules are not changed much, [73][74][75][76][77][78][79] it is unlikely that the observed isotope effect on the ET dynamics will arise through s . Similarly it is also unlikely that the isotopic substitutions will change the l or h values, because, for any vibrational mode the force constant and also the absolute displacement associated with the ET process is supposed to remain the similar for both normal and deuterated solutes.…”

Section: Deuterium Isotope Effect On the Et Dynamics In Ans-d2mentioning

confidence: 99%

“…Similarly it is also unlikely that the isotopic substitutions will change the l or h values, because, for any vibrational mode the force constant and also the absolute displacement associated with the ET process is supposed to remain the similar for both normal and deuterated solutes. [73][74][75][76][77] Regarding the low-frequency vibrational modes ͑q coordinate͒ in the 2D-ET model, it is assumed that the thermal energy (k B T) is sufficiently high with respect to the energies (h l ) of these modes. [44][45][46] Thus the low-frequency modes are treated classically.…”

Section: Deuterium Isotope Effect On the Et Dynamics In Ans-d2mentioning

confidence: 99%

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Ultrafast intermolecular electron transfer from orthomethoxyaniline to excited coumarin dyes

Pal

Shirota

Tominaga

et al. 1999

The Journal of Chemical Physics

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Ultrafast intermolecular electron transfer (ET) from orthomethoxyaniline (orthoanisidine, ANS) to a number of excited (S1) 4-trifluoromethyl-1,2-benzopyrones (coumarins) having differently substituted 7-amino group has been investigated by femtosecond fluorescence up-conversion technique. The ET dynamics in the present systems are nonsingle-exponential and occur faster than the diffusive solvation dynamics. The ET rates are largely dependent on the nature of the substituents at the 7-amino group of the coumarins. This dependence is well correlated with the free energy changes (ΔG0) for the ET reactions. The ET dynamics become slower on using deuterated ANS as the donor, where the amino group hydrogens of ANS are substituted by deuterium. The deuterium isotope effect, however, gradually reduces as the ET dynamics becomes faster. Conventional ET theories can not explain all the observations. The results are explained on the basis of the two-dimensional ET model, which considers the solvent coordinate and the intramolecular coordinate separately to depict the ET process. It is seen that in coumarin-ANS systems the ET occurs much faster than the coumarin-aniline systems. It is indicated that the electronic coupling matrix element, a parameter which determines the extent of interaction between the reactant and the product states in the ET process, is much larger in the present systems than for the coumarin-aniline systems. The deuterium isotope effect on the ET dynamics is explained in terms of the changes in the ΔG0 values on isotopic substitution of the solvent donors.

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Section: Deuterium Isotope Effect On the Et Dynamics In Ans-d2mentioning

confidence: 99%

Section: Deuterium Isotope Effect On the Et Dynamics In Ans-d2mentioning

confidence: 99%

Ultrafast intermolecular electron transfer from orthomethoxyaniline to excited coumarin dyes

Pal

Shirota

Tominaga

et al. 1999

The Journal of Chemical Physics

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“…section 4.3), λ l can also be considered to remain unchanged upon isotopic substitution. [63][64][65][66] It is thus (Table 3) are used for AN and AN-d7, but the other ET parameters are kept the same as in Figure 8a for both solvents.…”

Section: Isotope Effect Due To the Reorganization Energy (λ L ) Of Thmentioning

confidence: 99%

“…70,71 The origin of the zeropoint energy effect on ∆G°is that the isotopic substitution of a solute can reduce the frequencies of some of its vibrational modes, [63][64][65][66][67] and this in turn can reduce the zero-point energy of the deuterated solute. [63][64][65][66][67]70,71 If this reduction in the zeropoint energy is greater in the initial state than in the final state, it will cause a reduction in the driving force for the redox process of the deuterated solute. 70,71 In our cyclic voltammetric measurements, we observe that in a common solvent (acetonitrile) the oxidation potentials of both normal and deuterated anilines are the same within experimental error ( Table 2).…”

Section: Effect Of the Driving Force (∆G°)mentioning

confidence: 99%

Deuterium Isotope Effect on Ultrafast Intermolecular Electron Transfer

et al. 1996

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Deuterium isotope effects on ultrafast intermolecular electron transfer (ET) from electron-donating solvents such as aniline (AN) and N,N-dimethylaniline (DMA) to a number of excited (S 1 ) coumarin dyes have been investigated by a femtosecond fluorescence up-conversion technique. We carry out investigations using both normal and deuterated solvents and normal and deuterated coumarin dyes. With perdeuterated AN (AN-d 7 ) or amino-deuterated AN (AN-d 2 ), we observe almost the same extent of reduction in the ET rate constants as in normal AN. In the case of DMA, we do not observe any isotope effect upon substituting all of the N-methyl group hydrogens by deuterium (DMA-d 6 ). Using deuterated coumarins, where the 7-amino group hydrogens are substituted by deuterium, we do not observe any change in the ET dynamics. The effect of isotopic substitution of AN on the ET dynamics has been discussed in terms of the several ET parameters. Cyclic voltammetric measurements indicated that the isotopic substitution of the solvent AN causes a reduction in the driving force for the ET processes. It is inferred that the differences in the driving force for the normal and the deuterated AN as the donor solvent mainly arise from the solvent structural effects, caused by the intermolecular hydrogen bonding in this solvent. The present results also correlate well with the theoretical predictions of the two-dimensional ET model.

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“…Finally, it is important to note that the observation of KIE " 1 does not necessarily prove formal PT in the rate-determining step. For example, proton vibrational motion or displacement that does not result in PT can still be important to the reaction transition state geometry thus inducing a small KIE [39][40][41].…”

Section: Deuterium Kinetic Isotope Effectsmentioning

confidence: 99%

The Relation between Hydrogen Atom Transfer and Proton‐coupled Electron Transfer in Model Systems

Hodgkiss

Rosenthal

Nocera

2006

Hydrogen‐Transfer Reactions

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Quantum effects of high-frequency modes in inorganic electron transfer: kinetic isotope effects in redox reactions of hexaaquairon(2+) ion ([Fe(H2O)6]2+, hexa(aqua-d2)iron(2+) ion ([Fe(D2O)6]2+), and hexa(aqua-18O)iron(2+) ion ([Fe(18OH2)6]2+)

Cited by 36 publications

References 2 publications

Ultrafast intermolecular electron transfer from orthomethoxyaniline to excited coumarin dyes

Ultrafast intermolecular electron transfer from orthomethoxyaniline to excited coumarin dyes

Deuterium Isotope Effect on Ultrafast Intermolecular Electron Transfer

The Relation between Hydrogen Atom Transfer and Proton‐coupled Electron Transfer in Model Systems

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