Vibration assignment of carbon-sulfur bond in 2-thione-1,3-dithiole-4,5-dithiolate derivatives

The higher frequency peak near 1050 cm(-1) of the doublet in the infrared and Raman spectra of 2-thione-1,3-dithiole-4,5-dithiolate (DMIT) derivatives corresponds mainly to the stretching vibration of carbon-sulfur double bond in the terminal S=CS2 fragments of DMIT skeletons while the lower one corresponds mainly to the Fermi resonance peak between overtones of symmetric stretching vibration of two carbon-sulfur single bond in the S=CS2 fragment of DMIT skeletons and the higher frequency. On the other hand, the higher frequency near 500 cm(-1) corresponds mainly to the symmetric stretching vibration of two carbon-sulfur single bond in the S=CS2 fragments of DMIT skeletons while the lower one corresponds mainly to the symmetric stretching vibration of the four carbon-sulfur single bond in the S2C=CS2 fragments of DMIT skeletons.