Infrared and visible absorption spectra and photochemistry of the Ch2FX+, CHFX+, F–H⋅⋅⋅(CHX)−, and X–H⋅⋅⋅(CHF)− molecular ions in solid argon

Samples of CH2FX (where X=Cl, Br, I), 13CH2FCl, and CD2FCl at high dilution in argon were deposited at 15 K and simultaneously photoionized by argon resonance radiation from a microwave discharge, and the products studied by infrared and visible-ultraviolet spectroscopy. A large number of new absorptions were observed which have been grouped by photolysis, diffusion, and isotopic data. The parent cations CH2FX+ show increased C–X stretching frequencies and decreased C–H stretching frequencies relative to the neutral molecule. The daughter cations CHFX+ show increased C–F stretching and H–C–F hydrogen deformation frequencies, indicative of the enhanced pi bonding in the planar cation compared to the neutral radical. The C–F and C–X stretching vibrations of the neutral CFX carbenes are also identified. Strong, broad absorptions showing small carbon-13 and large deuterium shifts are assigned to the F–H stretching and hydrogen deformation modes of the intramolecular hydrogen-bonded parent anion F–H⋅⋅⋅(CHX)−, while other absorptions showing the proper isotopic shifts are assigned to the X–H and C–F stretching vibrations of the hydrogen-bonded species X–H⋅⋅⋅(CHF)−.