The purpose of this investigation was to study weak interactions between fluorinated ethylenes and carbon dioxide. Gas-phase complexes of fluoroethylene (FE)…CO2, 1,1-difluoroethylene (DFE)…CO2, and 1,1,2-trifluoroethylene (TFE)…CO2 were studied using chirped-pulse Fourier-transform microwave spectroscopy. Precise orientations of each complex were determined by analysis of spectra of several isotopologues for each dimer. All of the complexes form CH…O contacts between a CH group of the ethylene and an oxygen atom of CO2. In the FE and TFE complexes, CO2 may align either on the FCCH side or FCH end of the ethylene molecule, giving a planar overall structure. Both orientations were observed for FE…CO2, while only the end configuration was seen for TFE…CO2 and a side configuration was observed for DFE…CO2. To assign the rotational spectra of these complexes, experimental data was compared to ab initio predictions. Although ab initio calculations indicated lowest energy orientations of the FE and DFE complexes that were nonplanar with CO2 molecules positioned above the ethylene molecules, they did predict a planar minimum energy structure for TFE…CO2 that agreed with the experimental result. Experimental procedures, comparisons between orientations of all complexes, as well as differences between ab initio and experimental results will be discussed.

Structures and CH...O interactions of fluorinated ethylene…carbon dioxide complexes as determined by microwave spectroscopy

249th National Meeting (2015)

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