Charge recombination in excited donor-acceptor complexes with two absorption bands

Ionkin, Vladimir N.; Ivanov, Anatoly I.; Vauthey, Eric

doi:10.1134/s0036024409040281

Cited by 15 publications

(22 citation statements)

References 32 publications

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“…The two-staged regime most clearly manifests if the solvent reorganization energy noticeably exceeds the CR free-energy gap (black solid line in frame C in Figure ). Otherwise, the CR kinetics closely approaches the single-nonequilibrium-stage regime for strong and intermediary exergonic CR and with an increase in electronic coupling …”

Section: Results and Discussionmentioning

confidence: 88%

“…Otherwise, the CR kinetics closely approaches the single-nonequilibrium-stage regime for strong and intermediary exergonic CR and with an increase in electronic coupling. 57…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Within the framework of the stochastic point-transition approach, ,,,,,,,,− the CR kinetics of the excited DACs can be described by a set of differential equations for the probability distribution functions Here, ρ R ( Q 1 , Q 2 , t ) and ρ P ( n⃗ ) ( Q 1 , Q 2 , t ) are the probability distribution functions for the electronic excited state (reactant) formed by a short laser pulse in the charge transfer band and the neutral ground state (product) with the excitation of n α ( n α = 0, 1, 2, ...) vibrational quanta for αth intramolecular DAC modes with frequency Ω α (α = 0, 1, 2, ..., M ). Vector n⃗ has M components ( n 1 , n 2 , ..., n α , ..., n M ).…”

Section: Theory and Computational Detailsmentioning

confidence: 99%

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Dynamic Solvent Effect on Ultrafast Charge Recombination Kinetics in Excited Donor–Acceptor Complexes

2016

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Manifestation of the dynamic solvent effect (DSE) on the charge recombination (CR) kinetics of photoexcited donor-acceptor complexes in polar solvents has been investigated within the framework of the multichannel stochastic model. The model takes into account the reorganization of both the solvent and a number of intramolecular high-frequency vibration modes as well as their relaxation. The non-Markovian solvent dynamics is described in terms of two relaxation modes. The similarities and differences inherent to ultrafast charge transfer reactions occurring in the nonequilibrium and thermal regimes have been identified. The most important differences are as follows: (1) the DSE is strong in the area of weak exergonicity and is weak in the area of strong exergonicity for thermal reactions, whereas for the nonequilibrium reactions, the regions of strong and weak DSEs are reversed; (2) an increase in the electronic coupling value results in a decrease in the magnitude of DSE for nonequilibrium electron transfer and in its increase for the thermal reactions; and (3) the two-staged regime most clearly manifests if the reorganization energy of the relaxation modes noticeably exceeds the CR free-energy gap. With an increase in electronic coupling, the kinetics approaches the exponential regime because in the limit of strong electronic coupling, the reaction includes only single, nonequilibrium, stage.

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Section: Results and Discussionmentioning

confidence: 88%

“…Otherwise, the CR kinetics closely approaches the single-nonequilibrium-stage regime for strong and intermediary exergonic CR and with an increase in electronic coupling. 57…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Theory and Computational Detailsmentioning

confidence: 99%

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Dynamic Solvent Effect on Ultrafast Charge Recombination Kinetics in Excited Donor–Acceptor Complexes

2016

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“…The second, much slower, stage was detected only in a fast solvent (ACN), and it disappeared in slower solvents, valeronitrile and octanonitrile. Modeling the kinetics of charge recombination confirmed that its efficiency at the nonequilibrium stage increases with increasing the solvent relaxation time, which greatly reduces the yield of the thermalized excited state, and its decay becomes invisible in the experimental transition spectra in slow solvents …”

Section: Resultsmentioning

confidence: 97%

Modeling Kinetics of Ultrafast Photoinduced Intramolecular Proton-Coupled Electron Transfer

2018

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A model of photoinduced intramolecular proton-coupled electron transfer is derived. The model includes three states as follows: the ground, excited, and product states. The charge transfer is associated with both stages, photoexcitation and product formation. A larger part of the model parameters can be extracted from the stationary absorption and fluorescence spectra of a particular fluorophore. Two different reaction coordinates are associated with the two stages, which are not independent. The angle between the reaction coordinates strongly influences on the kinetics of ultrafast product formation. The stochastic multichannel approach is exploited for simulations of the kinetics. The simulations well reproduce the kinetics of ultrafast intramolecular protoncoupled electron transfer in 2-((2-(2-hydroxyphenyl)benzo[d]oxazol-6-yl)methylene)malononitrile in a few solvents. The transfer is shown to occur totally or partly, depending on the solvent, in the nonequilibrium regime. Analysis of the kinetics of the excited-state decay has uncovered a significant decrease in the magnitude of the reorganization energies of slow nuclear modes with increasing the solvent polarity. Such an unusual behavior of the total reorganization energy can be rationalized under the assumptions: (i) a slow intramolecular reorganization of a significant magnitude associates with the transition between excited and product states and (ii) intramolecular slow reorganization is accompanied by a change in the dipole moment of the fluorophore.

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“…The kinetics of ET between individual vibrational sublevels can be described in the framework of the stochastic approach generalized to account for the decay of both the reactant and the product states. A set of two coupled differential equations ,,,,,− for the probability distribution functions along the reaction coordinate, Q , for the reactant state, ρ r ( Q , t ), and the product state, ρ p ( Q , t ) is solved analytically by Green’s function method. Here, ℏ is the Planck constant, and δ( Q ) is the Dirac delta function.…”

Section: Theory and Computational Detailsmentioning

confidence: 99%

Effect of Reactant and Product State Decay on Ultrafast Charge-Transfer Kinetics: Violation of the Principle of Independence of Elementary Chemical Reactions

Михайлова

Ivanov

2017

J. Phys. Chem. C

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Fast decay of both the reactant and product states is shown to strongly increase the intrinsic electron transfer rate in donor−acceptor dyads. The decay is associated with redistribution/ relaxation of excited vibrational states that typically participate in the reaction. Although the role of the reorganization of high-frequency vibrational modes in electron-transfer dynamics is well understood and it is commonly accepted to strongly affect the ultrafast electron transfer dynamics, the influence of the relaxation of excited vibrational states on electron transfer is not accounted for in experimental data analysis. In photoinduced electron transfer, excited states of high-frequency vibrational modes are often produced by laser pump pulse so that the ultrafast charge separation, at least partly, occurs from excited vibrational states. The charge recombination accompanying the charge separation also essentially occurs from excited vibrational states of intermediates to form a final excited vibrational state. Since the decay of the reactant state and electron transfer are two elementary chemical reactions occurring in parallel, the influence of vibrational relaxation on the intrinsic electron-transfer rate constant is a clear manifestation of the violation of the fundamental principle of chemical kinetics postulating the independence of elementary chemical reactions. The mechanism of the violation is discussed in detail. The transition probability that better characterizes the efficiency of ultrafast nonequilibrium charge recombination than the rate constant is calculated. The dependencies of the electron-transfer rate constant and the transition probability on the product decay time are predicted to be identical while on the reactant decay time to be opposite.

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Charge recombination in excited donor-acceptor complexes with two absorption bands

Cited by 15 publications

References 32 publications

Dynamic Solvent Effect on Ultrafast Charge Recombination Kinetics in Excited Donor–Acceptor Complexes

Dynamic Solvent Effect on Ultrafast Charge Recombination Kinetics in Excited Donor–Acceptor Complexes

Modeling Kinetics of Ultrafast Photoinduced Intramolecular Proton-Coupled Electron Transfer

Effect of Reactant and Product State Decay on Ultrafast Charge-Transfer Kinetics: Violation of the Principle of Independence of Elementary Chemical Reactions

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