10min:

YOSHIO TATAMITANI, YASUFUMI SUZUKI, TERUHIKO OGATA, Department of Chemistry,
Faculty of Science, Shizuoka University, Shizuoka, Japan 422-8529.

The microwave spectra of van der Waals complexes of difluoromethane(DFM) and 1,1-difluoroethene(DFE)/ trifluoroethene(TFE) CH₂F₂ CF₂=CH₂ and CH₂F₂ CF₂=CHF have been observed using a Fourie transform microwave spectrometer from 5 to 19 GHz. The samples of 1% DFM and DFE/TFE in Ar were used to form the complexes in a super sonic expansion. For DFM DFE, 48 a-type transitions were assigned and 72 a- and b-type transitions were assigned for DFM TFE. The rotational and centrifugal distortion constants have been determined, leading to the molecular structures of DFM DFE and DFM TFE complexes. Both complexes were found to be C_s symmetry and bound with triple hydrogen bonds: One is the strong F HC type and two are the weaker CH F type. Molecular structures of these complexes are, however, quite different from each other. For DFM DFE, the out of plane atoms are two hydrogens which are bonded to a fluorine in DFE and a fluorine in DFM is bonded to a hydrogen in DFE. For DFM TFE, the out of plane atoms are two fluorines which attach to a hydrogen in DFE and a fluorine in DFM is bonded to the hydrogen in the same carbon of DFE. Ab initio MO calculations of MP2/6-311+G(d,p) lebel have supported these experimental results.