Knowledge Bank

Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of water (H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O) with hexafluorobenzene (C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$). Co-deposition experiments with H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O and C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ were performed at 17 K using nitrogen and argon as the matrix gases. New infrared bands attributable to the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O-C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ 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$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ 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$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O and HDO), and by matrix annealing experiments. Theoretical calculations were also performed for the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O-C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ complex using ab initio and density functional theory methods. In general, the calculations predict the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O and C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ vibrational frequencies in the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O-C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ complex to be shifted with respect to the H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O and C$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$F$\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$ monomers by similar magnitudes as to what we observe experimentally, lending support to our assignments.