Rotational Spectrum and Structure of the 1,1-Difluoroethylene···Carbon Dioxide Complex

Rotational spectra for five isotopologues of the 1:1 weak complex between 1,1-difluoroethylene (H₂CCF₂) and carbon dioxide (CO₂) have been measured using 480 MHz bandwidth chirped-pulse and resonant cavity Fourier-transform microwave spectroscopy between 5.5 and 18.5 GHz. The observed structure of the complex is planar, with the CO₂ aligned roughly parallel to the CC bond, and experimental structural parameters derived from rotational constants are consistent with the most stable geometry predicted by basis set superposition error and zero point energy corrected <i>ab initio</i> geometry optimizations at the MP2/6-311++G­(2d,2p) level. Comparisons with the recently characterized vinyl fluoride···carbon dioxide complex reveal slightly longer intermolecular distances in the present complex, but very similar binding energies