Molecular structures of (trifluoromethyl)iodine dihalides CF_3IX_2 (X = F, Cl): ab initio and DFT calculations

摘要

Ab initio and density functional theory calculations have been performed to investigate the equilibrium molecular structures, rotational barriers, vibrational spectra of (trifluoromethyl)iodine dihalides, CF_3IX_2(X = F, Cl), with the several basis sets. For each molecule the eclipsed form is found to be more stable than the staggered form. The staggered conformer corresponds to the transition state structure of which energy barrier is less than ～0.5 kcal/mol. The natural bond orbital analysis at the restricted Hartree-Fock level shows that the energy preference of an eclipsed form over a staggered form is primarily due to the σ_(IX) → σ_(CF) interactions