Infrared and Raman spectra, DFT-calculations and spectral assignments of 1,1,3,3,5,5-hexafluoro-1,3,5-trisilacyclohexane

The infrared and Raman spectra of 1,1,3,3,5,5-hexafluoro-1,3,5-trisilacyclohexane (c-C3H6Si3F6) as a solid powder have been recorded. The vibrational spectra reveal that the crystalline compound exists as a chair conformer with C3v symmetry at ambient temperature. Additional conformers such as twist or boat were not detected although quantum chemical calculations indicated a negligible energy difference between chair, twist and boat forms. The wavenumbers of the IR and Raman bands were measured and the assignments were initially supported by quantum chemical B3LYP/cc-pVTZ calculations in the harmonic approximation. These vibrational modes were scaled with a common factor of 0.98, and the 11 totally symmetric A1 and 16 doubly degenerate E fundamentals were assigned on the basis of the infrared and Raman intensities.