Comparison of the Kinetics of Electron Transfer in the Diffusion Limit for the Singlet and Triplet Quenching of Eosin Y by Quinones

Bertolotti, Sonia G.; Montejano, Hernán A.; Previtali, Carlos M.

doi:10.1111/php.12089

Cited by 4 publications

(3 citation statements)

References 48 publications

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“…This result compares well with that obtained using the Smoluchowski equation ,,, where D α is the diffusion coefficient of species α, R * is the “reaction” distance (here 13 Å), and N A is Avogadro’s number. Substituting the appropriate values for the parameters, we obtain 11 146 μM –1 s –1 .…”

Section: Results and Discussionsupporting

confidence: 85%

Diffusional Encounter Rate Constants for Xanthone and 2-Naphthoic Acid by Flash Photolysis Experiments and Brownian Dynamics Simulations: Substantial Effects of Polarizability of the Triplet State

2019

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Diffusional encounter rate constants, for xanthone and 2-naphthoic acid molecules in their triplet states with xanthone or 2-naphthoic acid molecules in their triplet or singlet states, were determined using nanosecond laser flash photolysis spectroscopy. Simultaneously, Brownian dynamics simulations were used to compute these rate constants for assumed models of encountering molecules. Altogether, a global fit to transient absorption progress curves, reporting populations of triplet state xanthone and triplet state 2-naphthoic acid molecules, allowed us to determine six diffusional encounter rate constants from our experiments. The most important result of this study is the detection of substantial effects of the electric polarizability of molecules in their triplet state, visible for xanthone triplet and 2-naphthoic acid ground states, a homo triplet–triplet annihilation of 2-naphthoic acid, and a hetero triplet–triplet annihilation for xanthone and 2-naphthoic acid.

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Section: Results and Discussionsupporting

confidence: 85%

Diffusional Encounter Rate Constants for Xanthone and 2-Naphthoic Acid by Flash Photolysis Experiments and Brownian Dynamics Simulations: Substantial Effects of Polarizability of the Triplet State

2019

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“…Lastly, there is the difference in spin states of the acceptors, as we are following the quenching of a triplet state rather than a singlet. There exist conflicting results as to whether spin multiplicity affects the observed k q relative to Δ G et , with some arguing there are no differences, and others reporting ,, lower k q values for triplet states at equivalent Δ G et .…”

Section: Resultsmentioning

confidence: 99%

Controlling Factors in the Rates of Oxidation of Anilines and Phenols by Triplet Methylene Blue in Aqueous Solution

et al. 2015

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Anilines and phenols are structurally similar compound classes that both are susceptible to oxidation by excited state triplet sensitizers but undergo oxidation by different mechanisms. To gain an understanding of the factors that control the rate of oxidation of anilines and phenols by triplet excited states, a kinetic study was performed on the oxidation of substituted anilines and phenols by methylene blue. The rate constants of one-electron transfer from anilines to triplet state methylene blue and their dependence on the reaction free energy are well fit to a Sandros-Boltzmann model. The observed rate constants are also well modeled when aniline oxidation potentials derived computationally are used. For phenols, the proton-coupled electron transfer rate constants were found to correlate primarily with O-H bond dissociation free energy and secondarily with phenol pKa. Rate constants for phenols could be modeled using computed bond dissociation free energies. These results provide a basis for predicting aniline and phenol oxidation rates, which could be valuable, for example, in assessing the likely persistence and fate of aniline- and phenol-based aqueous environmental pollutants.

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“…Not surprisingly, a substantial amount of research has been conducted on utilization of photo-induced electron transfer to initiate chemistry by involvement of a variety of transient intermediates, namely, singlet and triplet excited states, radical ion pairs, exciplexes, solvated radical ions, and radicals [11, 16, 17, 19-24, 29, 30]. In addition, theoretical aspects [12,14,28,[31][32][33][34] of electron transfer rates and the dynamics of such processes on ultrafast time scales [7,15,17,21,22,[25][26][27]34] have recently attracted much attention.…”

Section: Introductionmentioning

confidence: 99%

Quenching of diphenylmethyl radical fluorescence by cyanoaromatics and phenols

Cyr

Das

2015

Res Chem Intermed

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We have used double-laser nanosecond laser flash photolysis to study the kinetics of bimolecular quenching of the lowest doublet excited state of the transient diphenylmethyl radical ( 2 Ph 2 CH Á ) in acetonitrile at 25°C. We chose a series of cyanoaromatic compounds as acceptor-type quenchers and a series of 4-substituted phenols as donor-type quenchers. The observed bimolecular quenching rate constants (k Q ) are in the range 2 9 10 6 -2 9 10 10 M -1 s -1 for cyanoaromatics and 1 9 10 5 -3 9 10 9 M -1 s -1 for phenols. The Hammett plots of the k Q values for these two series have positive and negative slopes, respectively, and establish the enhanced behavior of the photo-excited diphenylmethyl radical as both a donor and an acceptor. For cyanoaromatics, the trend in the dependence of 2 Ph 2 CH Á * quenching rate constants on the free energy change of electron transfer (DG el ) coincides well with that of RehmWeller data on acceptor-type and donor-type quenchers of singlet excited states. An approximate fit of the k Q data for cyanoaromatics to the Agmon-Levine model of electron transfer gave a value of 4.5 kcal mol -1 for the free energy of activation at DG el = 0. For phenols, the trend in the dependence of k Q on the free energy change of electron transfer deviates significantly from that of cyanoaromatics data. This deviation was traced to the use of irreversible oxidation potentials of phenols to calculate DG el . No isotope effect is observed from substitution of phenolic hydrogen by deuterium, i.e., k Q,H /k Q,D & 1. Phenolate ions quench 2 Ph 2 CH Á * with large rate constants, 1-2 9 10 10 M -1 s -1 , i.e., well in the limit of diffusion control.

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Comparison of the Kinetics of Electron Transfer in the Diffusion Limit for the Singlet and Triplet Quenching of Eosin Y by Quinones

Cited by 4 publications

References 48 publications

Diffusional Encounter Rate Constants for Xanthone and 2-Naphthoic Acid by Flash Photolysis Experiments and Brownian Dynamics Simulations: Substantial Effects of Polarizability of the Triplet State

Diffusional Encounter Rate Constants for Xanthone and 2-Naphthoic Acid by Flash Photolysis Experiments and Brownian Dynamics Simulations: Substantial Effects of Polarizability of the Triplet State

Controlling Factors in the Rates of Oxidation of Anilines and Phenols by Triplet Methylene Blue in Aqueous Solution

Quenching of diphenylmethyl radical fluorescence by cyanoaromatics and phenols

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