Computational methods for intramolecular electron transfer in a ferrous-ferric iron complex

Journal Article · Fri Jul 29 04:00:00 EDT 2011 · Journal of Colloid and Interface Science, 361(1):293-306

DOI:https://doi.org/10.1016/j.jcis.2011.05.070· OSTI ID:1021278

Zarzycki, Piotr P; Kerisit, Sebastien N; Rosso, Kevin M

The limitations of common theoretical and molecular computational approaches for predicting electron transfer quantities were assessed, using an archetypal bridged ferrous-ferric electron transfer system in aqueous solution. The basis set effect on the magnitude of the electronic coupling matrix element computed using the quasi-diabatic method was carefully examined, and it was found that the error related to a poor basis set could exceed the thermal energy at room temperature. A range of approaches to determining the external (solvent) reorganization energy were also investigated. Significant improvements from the Marcus continuum model can be obtained by including dipolar Born-Kirkwood-Onsager correction. In this regard we also found that Klamt’s Conductor-Like Screening Model (COSMO) yields estimations of the external reorganization energy similar to those obtained with explicit solvent molecular dynamics simulations, if the fast-frequency modes are neglected, which makes it an attractive alternative to laborious umbrella sampling simulations. As expected, dielectric saturation observed in the first solvation shell decreases the curvature of the potential energy surface, but it nonetheless remains a quadratic function of the reaction coordinate. The linearity of solvent response to the charge redistribution was assessed by analyzing the energy gap autocorrelation function as well as the solvent density and dipole moment fluctuations. Molecular dynamics was also used to evaluate the sign and magnitude of the solvent reorganization entropy, to determine its effect on the predicted electron transfer rate. Finally, we present a simple way of estimating the vibration frequency along the reaction coordinate, which also enables prediction of the mass dependent isotopic signature of electron-transfer reactions.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1021278
• Report Number(s): PNNL-SA-70607; 25629; KC0303020
• Journal Information: Journal of Colloid and Interface Science, 361(1):293-306, Journal Name: Journal of Colloid and Interface Science, 361(1):293-306 Journal Issue: 1 Vol. 361; ISSN 0021-9797
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AQUEOUS SOLUTIONS
DIELECTRIC MATERIALS
DIPOLE MOMENTS
ELECTRON TRANSFER
ENERGY GAP
ENTROPY
Environmental Molecular Sciences Laboratory
FLUCTUATIONS
FORECASTING
IRON
MATRIX ELEMENTS
POTENTIAL ENERGY
SAMPLING
SATURATION
SOLVATION
SOLVENTS