CHARACTERIZATION OF A WATER-HEXAFLUOROBENZENE COMPLEX USING MATRIX ISOLATION INFRARED SPECTROSCOPY

Abstract

Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of water (H$_{2}$O) with hexafluorobenzene (C$_{6}$F$_{6}$). Co-deposition experiments with H$_{2}$O and C$_{6}$F$_{6}$ were performed at 17 K using nitrogen and argon as the matrix gases. New infrared bands attributable to the H$_{2}$O-C$_{6}$F$_{6}$ complex were observed near the asymmetric stretching, symmetric stretching, and bending vibrations of the water monomer and near the C-F and C-C stretching vibrations of the C$_{6}$F$_{6}$ monomer. Identification of the new infrared bands to those of the complex were established by comparing the co-deposition spectra with the spectra of the individual monomers, by performing experiments with isotopically labeled water (D$_{2}$O and HDO), and by matrix annealing experiments. Theoretical calculations were also performed for the H$_{2}$O-C$_{6}$F$_{6}$ complex using ab initio and density functional theory methods. In general, the calculations predict the H$_{2}$O and C$_{6}$F$_{6}$ vibrational frequencies in the H$_{2}$O-C$_{6}$F$_{6}$ complex to be shifted with respect to the H$_{2}$O and C$_{6}$F$_{6}$ monomers by similar magnitudes as to what we observe experimentally, lending support to our assignments.