Computational and spectroscopic ‍characterization of thianthrene.

In this work, we have carried out a comprehensive characterization of the vibrational spectroscopy of the non-planar molecule thianthrene. The combination of infrared, Raman and inelastic neutron scattering spectroscopies is highly complementary and allows all of the modes to be observed. Periodic density-functional theory calculations have provided unambiguous assignments of the spectra. The literature states that C-S stretch modes occur in the 600-800 cm -1 range. We find that while there are modes that involve sulfur motion in this region, this is a consequence of motion in the ortho -phenylene rings. The modes that are driven by the C-S stretches are found in the ~400-500 cm -1 range. The C-S-C bending modes occur in the 200-300 cm -1 range; these have not been previously characterized.