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An approach is developed that allows estimation of excited quadrupole molecule parameters responsible for changes in vibration frequencies in states with symmetry breaking by charge transfer from time-resolved IR spectra. The approach is tested on a molecule like A-π-D-π-A composed of an electron-accepting group A coupled with electron-donating group D by means of π-conjugated bonds, a D pyrrolopyrrole core, and two cyanophenyl acceptors. The expression derived for the IR spectrum of a molecule with symmetry breaking is shown to perfectly describe experimental data. The numerical values of the parameters of asymmetry in a series of solvents with different polarities and the solvent-independent parameters of the molecule itself are determined.

The dynamic solvent effect (DSE) in reactions of ultrafast proton-coupled electron transfer (PCET) under nonequilibrium conditions is studied. It is found in particular that the effect depends on angle φ between the directions of the reaction coordinates that correspond to the step of photoexcitation of the system, and to the step of product formation. Several trends characteristic of such reactions are established: (i) the highest DSE value should be observed in the region of the increased exergonicity of the reaction, and the effect is weak in the region of low exergonicity; (ii) upon an increase in the transition matrix element, the maximum in the curve of the dependence of the PCET rate constant on the reaction’s exergonicity shifts toward the region of lower values; (iii) the dependence of the effective reaction time on angle φ has a pronounced minimum, the position of which depends on the energy parameters of the reactants.

The effect of the carrier frequency of the exciting laser pulse on the kinetics of intramolecular photoinduced charge transfer in the multi-channel stochastic model is studied. It is shown that the population of different states of high-frequency intramolecular modes upon varying the frequency of the excitation pulse can considerably alter the rate constant of ultrafast charge transfer. It is found that a negative vibrational spectral effect is expected in the vicinity of a barrier-free area (the rate constant of photoinduced charge transfer decreases along with the carrier frequency of the excitation pulse), while a positive effect is predicted in areas of high and low exergonicity (an inverse dependence). It is concluded that the value of the spectral effect falls along with the time of vibrational relaxation. For ultrafast photo-induced charge transfer, however, it remains considerable up to relaxation times of 100 fs.

It is found that intramolecular and intermolecular electron transfer from the second singlet excited state of the donor in all molecular dyads studied up to now is accompanied by ultrafast recombination into the first excited state, resulting in a low quantum yield of the thermalized state with separated charges. The ultrafast photoinduced intramolecular charge transfer in donor‒acceptor 1‒acceptor 2 molecular triads is studied to ascertain the possibilities of increasing the quantum yield of ionic state. It is demonstrated that nonthermal (hot) electron transfer from the primary acceptor to the secondary acceptor can, in parallel with relaxation of a polar solvent, efficiently suppress the ultrafast recombination of charges into the first excited state of the donor and increase the yield of the ionic state. It is established that the angle between the directions of reaction coordinates corresponding to the electron transfer from the donor to the primary acceptor and from the primary acceptor to the secondary acceptor play the most important role in describing these processes. It is concluded that the value of this angle is governed by the ratio between the reorganization energies of the three possible electron transfers in the triad and can vary within wide limits. The parametric regions with maximum quantum yield of the thermalized ionic state are revealed. The strong effect the geometry of a studied triad has on charge separation efficiency is observed.

The U-shaped dependence of the rate constant of photoinduced intramolecular electron transfer vs. temperature observed for zinc-porphyrin-bridge-quinone donor-acceptor system in a 2-methyltetrahydrofuran solution is fitted using the stochastic multichannel model. The mechanism of this behavior is revealed. It is found that the drop in the rate upon the decline in temperature over the range of 320 to 125 K is related to two factors: the dynamic effect of the solvent (the increased relaxation time of solvent) and the low activation barrier. The substantial growth of the rate constant with the temperature drop in the range of 125 to 80 K is due to suppression of the dynamic effect of the solvent and a simultaneous lowering of the activation barrier due to the increased exergonicity of the reaction.

The processes of intramolecular electron transfer from the second excited electron state accompanied by superfast reverse transfer to the first excited state are studied. The kinetics of the populations of the first and second excited states, along with that the charge-separated states, is calculated within the generalized stochastic model, taking into account the reorganization of the medium and intramolecular high-frequency vibrations. It is shown that variations in the relaxation rate of the high-frequency vibrational modes can change the population of the quenching products by a factor of two to three. It is established that in the case of the weak exothermicity of the charge separation process, the population of the charge-separated states declines upon an increase in the vibrational relaxation rate, while the population of the first excited state increases; in the region of high exothermicity, these dependences change to ones that are opposite. To reveal the scales of these effects in real systems, the kinetics of the photo-induced processes in the zinc-porphyrin derivatives, including electron-acceptor imide groups covalently coupled with porphyrin rings, are calculated. It is shown that the results from calculating the kinetics of the population of the first and the second excited states agree well with the experimental data on the kinetics of the fluorescence of these states. The absolute values of the population of the charge-separated state and the first excited state are determined. The key role of the hot electron transitions that occur in parallel with the relaxation of the medium and intramolecular vibrations in the considered process is shown.

The influence of spatial charge redistribution modeled by a change in the dipole moment of the reagent that experiences excitation on the dynamics of ultrafast photoinduced electron transfer was studied. A two-center model based on the geometry of real molecules was suggested. The model described photoexcitation and subsequent electron transfer in a donor-acceptor pair. The rate of electron transfer was shown to depend substantially on the dipole moment of the donor at the photoexcitation stage and the direction of subsequent electron transfer. These parameters also determined the most important characteristic of ultrafast photoinduced electron transfer, the angle ϑ between the reaction coordinates corresponding to these reaction stages. The regions of model parameters corresponding to the strongest influence of the carrier frequency of the exciting pulse on the rate of electron transfer were established.