DFT STUDY OF THE STRUCTURE, CONFORMATIONAL PROFILE AND THE VIBRATIONAL ANALYSIS OF 2-FURANCARBOTHIALDEHYDE AND 3-FURANCARBOTHIALDEHYDE

The aim of this work is to study theoretically the geometrical structure, conformational preference, and vibrational properties of rotational isomers of 2- and 3-furancarbothialdehyde. The B3YLP hybrid density functional with the standard 6-311++G basis set is used to carry out all the calculations. The potential energy profile is calculated to determine the more stable conformer. The energy differences between cis and trans conformers show that the trans conformers are the preferred conformers with 0.70 kcal/mol and 1.36 kcal/mol for both 2-furancarbothialdehyde and 3-furancarbothialdehyde respectively. Nine different solvents with the polarity ranging from e = 1.92 to e = 78.39 are used to study the effect of solvation on the conformational stability of the two molecules using the integral equation formalism in the polarizable continuum model (IEF-PCM). The trans conformers are found to be more stable than the cis conformers in the gas phase. For 3-furancarbothialdehyde, the stability of the cis conformer increases as the dielectric constant of the solvent increases. On the other hand, the solvent reverses the conformational stability of 2-furancarbothialdehyde. The cis conformer becomes less stable as the dielectric constant of the solvent increases. The simulated infrared spectra of the molecules, geometrical parameters, and assignments of the vibrational modes are reported. Variations of the relative energy, dipole moment, and solvation energies as a function of the dielectric constant of solvents are investigated.