Nonequilibrium Ultrafast Charge Transfer Reactions in Photoexcited Donor-Acceptor Pairs

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

“…In the calculations, V el is varied in the range from 0.02 to 0.12 eV because the best fitting to the experimental data on the CR rate constant dependence on the free-energy gap 41−44 was obtained with the values from this area. 52,53 The results of numerical simulations, Figure 4, show a monotonic increase in the CR rate constant, k CR , with increasing V el . However, in all cases, this dependence is substantially weaker than that expected in the nonadiabatic regime where it is quadratic.…”

“…Here, the variable model parameters are the second solvent relaxation time, τ 2 ; the free-energy gap, −Δ G CR ; and the intramolecular, E rv , and solvent, E rm , reorganization energies. In the calculations, V el is varied in the range from 0.02 to 0.12 eV because the best fitting to the experimental data on the CR rate constant dependence on the free-energy gap − was obtained with the values from this area. , …”

“…Further development of this idea showed that the reorganization of the high-frequency vibrational modes plays a paramount role, strongly increasing the rate constant of not only strongly but also weakly exergonic nonequilibrium CR. − Hence, for a quantitative description of the CR kinetics of the photoexcited DACs, their real spectrum of intramolecular high-frequency modes should be employed. Such an intracomplex vibrational spectrum typically includes 5–10 active modes. , The decay of excited vibrational states due to intramolecular vibrational redistribution and relaxation can also significantly affect the CR kinetics. , The stochastic model involving reorganization of the solvent and several intramolecular high-frequency vibrational modes of a DAC was able to fit the CR rate constant dependence on the free-energy gap , obtained in the experiments. − …”

“…49,51 The decay of excited vibrational states due to intramolecular vibrational redistribution and relaxation can also significantly affect the CR kinetics. 48,50 The stochastic model involving reorganization of the solvent and several intramolecular high-frequency vibrational modes of a DAC was able to fit the CR rate constant dependence on the free-energy gap 52,53 obtained in the experiments. 41−44 The nonequilibrium ultrafast CR is a key elementary stage of diverse photoinduced ET reactions.…”