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 ab initio 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.