ABINITIO VIBRATIONAL FREQUENCIES OF THE TRIFLATE ION, (CF3SO3)-

The optimized geometry, harmonic vibrational frequencies and infrared intensities of the trifluoromethanesulfonate (triflate) ion, CF3SO3-, have been determined with ab initio self-consistent Hartree-Fock theory by using 3-21G* and 6-31G* Gaussian basis sets. Second-order Moller-Plesset perturbation calculations were also carried out with 6-31G* basis. A normal mode analysis shows that the vibrations assigned as symmetric and antisymmetric CF3 stretching involve other internal coordinates as well, viz., CF3 bending and CS stretching. The corresponding SO3 stretching modes, on the other hand, are almost entirely described with SO stretching coordinates. The assignments of the symmetric and antisymmetric SO3 and CF3 stretching vibrations from Moller-Plesset theory are seen to be different from those reported in the literature. Recent infrared spectroscopic experiments of the triflate ion coordinated to the zinc or lead ion in poly(ethylene oxide) complexes support the conclusions from second-order perturbation theory. The vibrational frequencies and infrared intensities show a strong dependence on basis set and electron correlation.