期刊
CHEMICAL PHYSICS
卷 319, 期 1-3, 页码 4-15出版社
ELSEVIER
DOI: 10.1016/j.chemphys.2005.03.037
关键词
electron transfer; reorganization energy; molecular dynamical simulation; inertial polarization; inertialess polarization
Outersphere reorganization energies (gimel) for intramolecular electron transfer (ET) and hole transfer are studied in anion- and cation-radical forms of complex organic substrates (biphenylyl-spacer-naphtyl) in polar solvents simulated by means of the nonpolarizable models of water and 1,2-dichloroethane. The earlier elaborated molecular/continuum approach (the MD/FRCM, J. Chem. Phys., 119 (2003) 8024) is used; this method provides a physically relevant background for separating inertial and inertialess polarization responses within a nonpolarizable MD simulation (the SPC water model). Quantum-chemical calculations of solute charge distributions were performed with semiempirical (AMI) and second ab initio (HF/6-31G(d,p)) approximations. Ab initio charges give lower A-values and are preferable, probably, because of including the effect of the SCRF polarization of the diabatic ET states. Standard Lennard-Jones and charge parameters implemented in MD runs were not specially fitted for reproducing ET effects. The difference in values for a cation and an anion originating from the same parent structure was specially investigated. As shown earlier, this effect, nonlinear in its nature, proved to be extremely large when a model dipolar two-site system was studied. For the present ET structures representing real chemical substrates it has reduced to a plausible value of 6-8 kcal/mol. The study of the temperature dependence of A comprises a first MD simulation of this problem and its slope was found to be in accord with an experimental observation for an anionic species. Calculations of absolute gimel-values for the hole transfer in 1,2-dichloroethane are the first MD simulations of reorganization energies in experimentally studied reactions. Computed values of gimel-s are higher than the experimental data. The effect of this magnitude could be eliminated by proper tuning the solvent parameters. (c) 2005 Elsevier B.V. All rights reserved.
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