Pierre-André Cazade, Halina Tran, Tristan Bereau, Akshaya K. Das, Felix Kläsi, Peter Hamm, and Markus Meuwly, J. Chem. Phys. (2015)

Influence of fluorine on solvent dynamics from atomistic simulations with multipoles and 2D-IR spectroscopy

The solvent dynamics around fluorinated acetonitrile is characterized by 2-dimensional infrared spectroscopy and atomistic simulations. The lineshape of the linear infrared spectrum is better captured by semiempirical (density functional tight binding) mixed quantum mechanical/molecular mechanics simulations, whereas force field simulations with multipolar interactions yield lineshapes that are significantly too narrow. For the solvent dynamics, a relatively slow time scale of 2 ps is found from the experiments and supported by the mixed quantum mechanical/molecular mechanics simulations. With multipolar force fields fitted to the available thermodynamical data, the time scale is considerably faster–on the 0.5 ps time scale. The simulations provide evidence for a well established CF–HOH hydrogen bond (population of 25%) which is found from the radial distribution function g(r) from both, force field and quantum mechanics/molecular mechanics simulations.