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

The infrared spectra of 1,3,5-trisilacyclohexane (c-C3H6Si3H6) as a vapour and liquid have been recorded. Raman spectra of the liquid have been studied and depolarization data were obtained. The compound exists in the stable form as a chair conformer with C3v symmetry, and additional conformers such as twist or cradle forms were not detected. The wavenumbers of the IR and Raman active vibrational modes were measured and their existence were supported by quantum chemical B3LYP/cc-pVTZ calculations in the harmonic approximation. The 11 totally symmetric A1 and 16 doubly degenerate E fundamentals were assigned on the basis of the infrared vapour contours and intensities and upon the Raman intensities and depolarization measurements. Quantum chemistry calculations support the assignments: an average relative deviation between observed and calculated wavenumbers of 2.2% was obtained employing scaling of the harmonic B3LYP/cc-pVTZ force field, which was reduced to 1.4% in the anharmonic calculations.