Isotope Effect of Proton/Deuteron Diffusion Constant in Ice

Uritski, Anna; Presiado, Itay; Huppert, Dan

doi:10.1560/ijc.49.2.235

Cited by 3 publications

(3 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to prevent the “guest” molecule (QCy7) from being expelled from the bulk of the ice during sample freezing, we added to the liquid water a small amount of a cosolvent of 0.5 mol % methanol. In previous studies of methanol-doped ice with organic photoacids as salts like naphthol sulfonates, we found that low concentrations of methanol prevent the aggregation of the photoacid molecule on the microcrystalline surface of the ice upon freezing of the sample. − At high temperatures ( T ≥ 185 K), the emission spectrum of QCy7 in ice is similar to that in water. The spectrum consists of a weak band with a peak at ∼560 nm assigned to the protonated form, ROH, and a strong band with a peak at ∼700 nm attributed to the deprotonated form, RO – .…”

Section: Resultsmentioning

confidence: 80%

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

et al. 2013

Self Cite

View full text Add to dashboard Cite

Steady-state and time-resolved fluorescence techniques were used to study the temperature dependence of the photoprotolytic process of quinone-cyanine-7 (QCy7), a very strong photoacid, in H2O and D2O ice, over a wide temperature range, 85-270 K. We found that the excited-state proton-transfer (ESPT) rate to the solvent decreases as the temperature is lowered with a very low activation energy of 10.5 ± 1 kJ/mol. The low activation energy is in accord with free-energy-correlation theories that predict correlation between ΔG of reaction and the activation energy. At very low temperatures (T < 150 K), we find that the emission band of the RO(-)*, the deprotonated form of QCy7, is blue-shifted by ~1000 cm(-1). We attributed this band to the RO(-)*···H3O(+) ion pair that was suggested to be an intermediate in the photoprotolytic process but has not yet been identified spectroscopically.

show abstract

Section: Resultsmentioning

confidence: 80%

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…To prevent the “guest” molecule (QCy9) from being expelled from the bulk of the ice during freezing of the sample, we added to the liquid water a small amount of 0.5% mol methanol as a cosolvent. In previous studies of methanol-doped ice with organic photoacids as salts like naphthol sulfonates, we found that low concentrations of methanol prevent the aggregation of the photoacid molecule on the microcrystalline surface of the ice upon freezing of the sample. − At high-temperature ice ( T ≥ 185 K), the emission spectrum of QCy9 in ice is similar to that in water. The spectrum consists of a weak band with a peak at ∼500 nm assigned to the protonated form, ROH, and a strong band with a peak at ∼670 nm attributed to the deprotonated form, RO – .…”

Section: Resultsmentioning

confidence: 81%

Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D₂O Providing the Missing RO^–···H⁺ Ion-Pair Fingerprint

et al. 2014

Self Cite

View full text Add to dashboard Cite

Steady-state and time-resolved optical techniques were employed to study the photoprotolytic mechanism of a general photoacid. Previously, a general scheme was suggested that includes an intermediate product that, up until now, had not been clearly observed experimentally. For our study, we used quinone cyanine 7 (QCy7) and QCy9, the strongest photoacids synthesized so far, to look for the missing intermediate product of an excited-state proton transfer to the solvent. Low-temperature steady-state emission spectra of both QCy7 and QCy9 clearly show an emission band at T < 165 K in H2O ice that could be assigned to ion-pair RO(-)*···H3O(+), the missing intermediate. Room-temperature femtosecond pump-probe spectroscopy transient spectra at short times (t < 4 ps) also shows the existence of transient absorption and emission bands that we assigned to the RO(-)*···H3O(+) ion pair. The intermediate dissociates on a time scale of 1 ps and about 1.5 ps in H2O and D2O samples, respectively.

show abstract

“…Since these theoretical developments took place, the field of ESPT was reviewed several times, − acknowledging that the above theoretical model is in good agreement with ESPT from various ROH photoacids to water − and other solvents. ,− These include photoacids that are much more acidic than HPTS, as well as those exhibiting different excited-state lifetimes for acid and base and/or an additional quenching process by the photoemitted proton. ,− , Subsequently, two additional groups (those of Fayer and Douhal) have confirmed the applicability of the reversible GR diffusion model for HPTS kinetics, , as well as numerous additional measurements of other photoacids from both the Huppert and Pines laboratories. − …”

Section: Introductionmentioning

confidence: 97%

Reversible Excited-State Proton Geminate Recombination: Revisited

et al. 2016

Self Cite

View full text Add to dashboard Cite

About three decades ago, Pines and Huppert found that the excited-state proton transfer to water from a photoacid (8-hydroxy-1,3,6-pyrene trisulfonate (HPTS)) is followed by an efficient diffusion-assisted reversible geminate-recombination of the proton. To model the reaction, Pines, Huppert, and Agmon used the Debye-Smoluchowski equation with boundary conditions appropriate for reversible contact reaction kinetics. This reaction model has been used successfully to quantitatively fit the experimental data of the time-resolved fluorescence of HPTS and several commonly used photoacids. A consequence of the reversibility of this reaction is an apparent long-time tail of the photoacid fluorescence signal, obeying (after lifetime correction) a t power law asymptotics. Recently, Lawler and Fayer reported that in bulk water the observed power-law decay of the long-time fluorescence tail of HPTS is -1.1 rather than -1.5, as expected from the spherically symmetric diffusion model. In the current study, we reaffirm our previous reports of the power-law behavior of HPTS fluorescence. We also demonstrate that molecular-level complications such as the deviation from spherical symmetry, rotational dynamics, competitive proton binding to the sulfonate moieties of HPTS, distance-dependent diffusion coefficient, and the initial starting point of the proton can affect the observed kinetics only at intermediate times, but not at asymptotically long times. Theoretically, we analyze the rebinding kinetics in terms of the number of extrema of the logarithmic derivative, showing subtle effects on the direction of approach to the asymptotic line (whether from above or below), which also appears to be corroborated experimentally.

show abstract

Isotope Effect of Proton/Deuteron Diffusion Constant in Ice

Cited by 3 publications

References 56 publications

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D₂O Providing the Missing RO^–···H⁺ Ion-Pair Fingerprint

Reversible Excited-State Proton Geminate Recombination: Revisited

Contact Info

Product

Resources

About

Isotope Effect of Proton/Deuteron Diffusion Constant in Ice

Cited by 3 publications

References 56 publications

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

Temperature Dependence of the Excited-State Proton-Transfer Reaction of Quinone-cyanine-7

Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D2O Providing the Missing RO–···H+ Ion-Pair Fingerprint

Reversible Excited-State Proton Geminate Recombination: Revisited

Contact Info

Product

Resources

About

Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D₂O Providing the Missing RO^–···H⁺ Ion-Pair Fingerprint