Car-Parrinello molecular dynamics simulations and EPR property calculations on aqueous ubisemiquinone radical anion

Car-Parrinello molecular dynamics (CPMD) simulations have been performed on ubisemiquinone radical anion in aqueous solution. The different types of hydrogen bonding formed between the semiquinone and the solvent were studied in terms of frequency and directionality, in comparison with the parent benzosemiquinone radical anion. The EPR parameters (g-tensors and hyperfine coupling constants) were obtained from quantum chemical property calculations performed on snapshots along the MD trajectory, and the contributions of different solvation effects to the EPR parameters have been evaluated. The influence of the anion's conformational behaviour was examined, including the orientation-dependent effects of hyperconjugation on side-chain hyperfine coupling.