Effect of temperature on the EPR properties of a rhamnose alkoxy radical: A DFT molecular dynamics study

It has been shown previously that two distinctive variants (called RHop and RO4) exist of the radiation-induced rhamnose alkoxy radical. Density functional theory (DFT) calculations of the electron paramagnetic resonance (EPR) properties were found to be consistent with two separate measurements at different temperatures [E. Pauwels, R. Declerck, V. Van Speybroeck, M. Waroquier, Radiat. Res., in press]. However, the agreement between theory and experiment was only of a qualitative nature, especially for the latter radical. In the present work, it is examined whether this residual difference between theoretical and experimental spectroscopic properties can be explained by explicitly accounting for temperature in DFT calculations. With the aid of ab-initio molecular dynamics, a temperature simulation was conducted of the RO4 variant of the rhamnose alkoxy radical. At several points along the MD trajectory, g and hyperfine tensors were calculated, yielding time (and temperature) dependent mean spectroscopic properties. The effect of including temperature is evaluated but found to be within computational error. (C) 2007 Elsevier B.V. All rights reserved.