Effects of hydrogen bond and solvent polarity on the C=O stretching of bis(2-thienyl)ketone in solution.

The optimized structural parameters, the absorption and the resonance Raman spectra have been investigated for the bis(2-thienyl)ketone in gas phase, in cyclohexane, methanol, and acetonitrile solvents by means of time dependent density functional theory calculations, the solvent electronic polarization effect on the solvation shift is examined and in well accordance with the calculation. The effect of increasing the polarity of the solvent is well represented by the polarizable continuum model, both for the absorption spectra and resonance Raman intensities. The Raman spectra of the C=O stretching mode, which is sensitive to the intermolecular interaction for bis(2-thienyl)ketone dissolved in solvents, were systematically studied. It was found that the hydrogen bond effect plays an important role in reducing the carbonyl stretching wavenumbers. The results of Raman shifts were interpreted through the dilution effect, solvation effects, and hydrogen bond-forming effects. Furthermore, the excitation profiles of several important Raman bands of bis(2-thienyl)ketone molecule in different solvents have been critically analyzed. The solvent effects on structural and symmetry properties of the molecule in S2 electronic state as well as the short-time photo relaxation dynamics have been discussed.

Resonance Raman intensity analysis of the A band short-time photochemical dynamics of 4,5-ethylenedithio-1,3-dithiole-2-thione.

Resonance Raman spectra (RRs) for 4,5-ethylenedithio-1,3-dithiole-2-thione (EDDT) were obtained with 397.9 and 416 nm excitation wavelengths, and density functional calculations were performed to elucidate the electronic transitions and the RRs of EDDT in chloroform solvent. The RRs indicate that the Franck-Condon region photodynamics have multidimensional character with nuclear motion predominantly along the C(4)═C(5) stretch and the C(4)═C(5) twist out-of-plane. Resonance Raman cross-sections of A-band absorption have been obtained for the vibrational modes of EDDT with its excitation frequencies spanning the 408 nm. Resonance Raman intensity analysis of the resulting RRs excitation profiles and absorption spectrum using a time-dependent wave packet formalism yields mode-specific nuclear displacement and vibrational reorganizational energies. The intensity analysis results for EDDT were compared to previously reported results for dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate (DDTD), which shows that the additional six-member heterocycle of EDDT strongly affects the reorganizational energy and energy participation. The authors briefly discuss the differences and similarities of the spectra in terms of molecular symmetry and electron density.

Investigation of excited state structural dynamics of bis(2-thienyl)ketone in the condensed phase using Raman, IR, and UV-visible spectroscopy aided by density functional theory calculation.

Detailed investigation on the vibrational and electronic spectra has been carried out in order to study various properties of bis(2-thienyl)ketone molecule in its ground and excited electronic states. To get insight into the structural and symmetry features of the molecule, resonance Raman spectra (RRs) of bis(2-thienyl)ketone have been acquired and the Raman excitation profiles of several normal modes have been analyzed, and density functional calculations were done to help the elucidation of the photo relaxation dynamics of A and B band electronic transitions. The RRs indicate that the photo relaxation dynamics for S(0)→S(2) excited electronic state is predominantly along the nominal the Ring breathing + ν(SynC(1)C(11) C(9)) stretch, ν(CO) + ν(C(2)C(3)) + ν(C(8)C(9)) stretch, and the γ(CH(I, II)) + γ(OC) stretch and simultaneously along the nominal γ(CH(II)) relaxation processes, while that for S(0)→S(5) is predominantly along the ν(CO) + ν(C(2)C(3)) + ν(C(8)C(9)) stretch ν(7) (1616 cm(-1)). The excited state short-time structural dynamics of bis (2-thienyl) ketone determined from RRs were interpreted with account of the Albrecht's theory and Herzberg-Teller contributions.