Photoelectron spectroscopy of hydrated hexafluorobenzene anions.

We present a synergetic experimental/theoretical study of hydrated hexafluorobenzene anions. Experimentally, we measured the anion photoelectron spectra of the anions, C6F6(-)(H2O)n (n=0-2). The spectra show broad peaks, which shift to successively higher electron binding energies with the addition of each water molecule to the hexafluorobenzene anion. Complementing these results, we also conducted density functional calculations which link adiabatic electron affinities to the optimized geometric structures of the negatively charged species and their neutral counterparts. Neutral hexafluorobenzene-water complexes are not thought to be hydrogen bonded. In the case of C6F6(-)(H2O)1, however, its water molecule was found to lie in the plane of the hexafluorobenzene anion, bound by two O-H...F ionic hydrogen bonds. Whereas in the case of C6F6(-)(H2O)2, both water molecules also lie in the plane of and are hydrogen bonded to the hexafluorobenzene anion but on opposite ends. This study and that of Schneider et al. [J. Chem. Phys. 127, 114311 (2007), preceding paper] are in agreement regarding the geometry of C6F6(-)(H2O)1.