We report the infrared photodissociation (IRPD) spectra of the fluoride-water cluster anion and provide the first experimental evidence for disentangling the hydrogen bonded OH stretch and the HOH bend. By examining the IRPD spectrum of the H2-tagged F-(H2O) complex, we identify strong coordination of molecular hydrogen by comparing the red-shifted fundamental band position (ΔνH-H 269 cm-1). Cryogenic ion-trap mass spectrometry provides insights into the coordination of the fluoride anion by stepwise solvation of H2 molecules and is presented in the elusive spectral fingerprint in the red-shifted hydrogen-bonded OH stretch. By subsequent H2 addition, the hydrogen-bonded OH stretch blue shifts and separates from the water bend. The agreement between experiment and ab initio computations suggest strong dispersion-type interaction of H2 and F-(H2O) ultimately decoding the otherwise elusive structure. Two-dimensional plots of the potential energy surface were constructed to illustrate the effects of H2 addition to the F-(H2O).

On the nature of the strong hydrogen-bond: Fluoride and water

2019 Spring National Meeting

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