Complexes of Carbon Dioxide with Dihalogenated Ethylenes: Structure, Stability and Interaction

© The Royal Society of Chemistry 2016. Interactions of ethylene and its 1,2-dihalogenated derivatives with CO2 induce the formation of twenty four molecular complexes with stabilization energies in the range of 1.1 to 7.5 kJ mol-1 as computed at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. The stability of the parent C2H4⋯CO2 complex is due to a π⋯π∗ interaction which has not yet been reported in the complexes of CO2-philic compounds and CO2. The cis-XCH=CHX⋯CO2 complexes are found to be slightly more stable than the trans-XCH=CHX⋯CO2, with X = F, Cl and Br. Generally, the overall stabilization energy of each complex is determined by the C-H⋯O hydrogen bond and the C-X⋯C Lewis acid-base interaction, in which the latter plays a larger role. Substitution of two H atoms in CH2=CH2 by the same halogen atoms stabilizes the complexes XCH=CHX⋯CO2, and for the same dihalogenated derivatives, the stability of XCH=CHX⋯CO2 tends to increase from X = F via Cl and to Br. The obtained results suggest that the contraction of the C-H bond involved in the C-H⋯O hydrogen bond and the blue-shift of its stretching frequency depend not only on a polarization of the C-H bond in the isolated monomer but also on the geometric shape of the complex formed.status: publishe