Resonance Raman intensity analysis of the excited-state photochemical dynamics of dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate in the A-band absorption

Dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate (DDTD) was synthesized and characterized using NMR, Fourier transform (FT)Raman, Fourier transform-infrared (FT-IR) and UV spectroscopies. Resonance Raman spectra (RRs) were obtained with 341.5, 354.7 and 368.9 nm excitation wavelengths and density functional calculations were carried out to elucidate the pi (S-C-S) -> pi* (S-C-S) electronic transitions and the RRs of DDTD in cyclohexane solution. The RRs indicate that the Franck-Condon region photo dynamics have a multidimensional character with motion predominantly along the C=5 stretch and the C-S symmetric stretch modes in the five-member heterocycle. A preliminary resonance Raman intensity analysis was carried out and the results for DDTD were compared with previously reported results for 1,3-dithiole-2-thione (DTT). Differences and similarities of the spectra in terms of molecular symmetry and electron density are also discussed. Copyright (C) 2010 John Wiley & Sons, Ltd.