Infrared spectra of HF complexes in noble-gas solids

Abstract

The very weak hydrogen-bonded complex of molecular hydrogen and HF has been prepared by condensing the neon-diluted reagents at 5 K. Infrared spectra of the H₂⋯HF complex revealed a ν_s(HF) stretching mode at 3938 cm^–1 and ν(H₂) mode at 4155 cm^–1, which are bathochromically shifted from the isolated molecule values of 15 and 6 cm^–1, respectively. The very strong NH₃⋯HF complex has been studied in solid neon and solid argon. The ν_s(HF) mode at 3215 cm^–1 in the gas phase is shifted to 3106 cm^–1 in solid neon and 3041 cm^–1 at solid argon. The ν₁(HF) librational mode appeared at 916 cm^–1 with 2ν₁ at 1679 cm^–1, while ν₂(NH₃) was hypsochromically shifted to 1093 cm^–1 in solid argon. The antihydrogen-bonded arrangement is the more stable structure for the HF⋯Cl₂ complex in the gas phase; however, solid argon and neon samples reveal both antihydrogen-bonded and hydrogen-bonded complexes. In the Cl₂⋯HCl case, evidence for only the hydrogen-bonded form was observed in solid argon