Rotational Spectrum, Structure, and Interaction Energy of the Trifluoroethylene···Carbon Dioxide Complex

Rotational spectra for four isotopologues of the 1:1 weakly bound complex between trifluoroethylene (HFC═CF₂) and carbon dioxide (CO₂) were recorded using 480 MHz bandwidth chirped-pulse and resonant cavity Fourier transform microwave spectroscopy between 5.0 and 18.5 GHz. Two planar forms are possible: experimental rotational constants, planar moments, and dipole moment components are consistent with the form in which CO₂ is positioned at the CHF end of the TFE subunit and is approximately perpendicular to the C═C bond; the other form, with CO₂ aligned roughly parallel to the C═C bond, is not observed, consistent with ab initio relative energy predictions. Symmetry-adapted perturbation theory (SAPT) calculations provided interaction energies for possible structural forms of this complex, and comparisons are made with this and other members of the series of carbon dioxide complexes with fluorinated ethylenes (vinyl fluoride, 1,1-difluoroethylene, cis- and trans-1,2-difluoroethylene, and trifluoroethylene).