Electron-transfer processes in a supramolecular triad system A1-D-A2 in a polar solvent are theoretically investigated where D and Ai stand for donor and acceptor subunits. Two relevant coordinates are introduced which represent the solvent polarization. Potential energy surfaces for the locally excited, (LE) and chargetransfer (CT) states of the supramolecular system are calculated by using the dielectric continuum approximation for the solvent polarization. The model may easily be generalized or verified by using a more realistic molecular description of the solvent polarization. The correlation coefficient of the two solvent polarization coordinates is analyzed as a function of the distances between the donor and the two acceptors in the triad system. The expressions for the rates of electron transfer are derived in the nonadiabatic limit on the basis of the potential energy surfaces calculated. The decay rate coefficient of the locally excited state in the supramolecular system is calculated for different values of the free energy change in the case of nonadiabatic electron transfer.
The three-potential surface problem of electron transfer in solution is analyzed using Zusmantype kinetic equations. The model describes ultrafast formation and recombination of radicalion pairs limited by solvent dielectric relaxation. The problem begins with a donor on an electronic excited state surface. The system evolves with crossing to the radical-ion pair surface (with the possibility of recrossing to the excited donor surface included). Solvent relaxation moves the system to lower energy on the radical-ion pair surface where crossing to the ground state neutral surface occurs (with the possibility of recrossing to the radical-ion surface included). Model calculations of the transient radical-ion pair populations are presented. The time dependent results that are presented show a dramatic dependence on the relative free energy differences (AG 's) among the three potential surfaces. Comparisons to other formalisms and to less detailed approximations are made. The mean populations of the transient species for a system of a donor and many acceptors in the absence of spatial diffusion are also derived.
Geometry and vibrational modes of the anthranilic acid molecule in the S(0) and S(1) states were computed using ab initio methods: Hartree-Fock (HF) and configuration interaction of singly excited configurations (CIS) as well as the density functional theory with time-dependent perturbation (TD-DFT). The intensity distribution in the laser-induced fluorescence excitation spectra was modeled in two ways: using displacement parameters for independent modes and using multidimensional Franck-Condon integrals. The change in the molecular geometry upon excitation was calculated from the band intensities within the above two models. Displacement parameters of eight in-plane modes active in the excitation spectrum were optimized to reproduce the experimental intensities of about 40 most intensive and well-separated vibrational bands, while displacement parameters of other in-plane modes were kept frozen at the values resulting from the quantum chemical calculations. The intramolecular hydrogen bond is significantly stronger in the S(1) state than in the ground state. Additionally, bond lengths and angles in the aromatic ring, within the substituents and between the ring and the substituents undergo significant changes and they induce the presence of strong fundamentals in the excitation spectrum.
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