Resonant Raman scattering in single crystals of BDNT, BDNT1+ and BDNT2+

Polarized Raman spectra of crystals of BDNT, BDNT-PF6, BDNT-(PF6)2 and BDNT-(ClO4)2-Cl2 have been obtained in the region 130–1700 cm−1. It is shown that due to a resonant character of the Raman spectra only the Ag modes of the intramolecular vibrations of the BDNT molecules were observed in the spectra of all the crystals. A low-frequency shift of the frequencies of the CC bands on increasing the oxidation degree is revealed which is due to charge transfer from the BDNT molecules to the acceptors PF6 or (ClO4)2. This shift was larger for the band corresponding to the stretching vibration of the CC bond which connected the dithiole and naphtho-thiadiazole rings. The Raman intensity of this band diminished strongly with the growth of oxidation, likely due to frustration of the bond conjugation. A molecular configuration in the crystals depends on the oxidation degree, but not on the acceptor type.