Structural and vibrational studies of the potential anticancer agent, 5-difluoromethyl-1,3,4-thiadiazole-2-amino by DFT calculations

作者：Romano Elida; Florencia Ladetto Maria; Antonia Brandan Silvia

来源：Computational and Theoretical Chemistry, 2013, 1011: 57-64.

DOI：10.1016/j.comptc.2013.01.016

• 5-Difluoromethyl-1,3,4 thiadiazole-2-amino
• DFT calculation
• Vibrational spectra
• Molecular geometry
• Force field

The structural and vibrational properties of a potential anticancer agent, the 5-difluoromethyl-1,3,4 thiadiazole-2- amino derivative and its tautomeric forms were studied by using the available experimental infrared and H-1, C-13 and F-19 NMR spectra and theoretical calculations based the density functional theory (OFT). The bonds order, atomic charges, charge-transfers and topological properties were studied by means of the Natural Bond Orbital (NBO) and the Atoms in Molecules theory (AIM) calculations. The harmonic vibrational wavenumbers for the optimized geometries were calculated at B3LYP/6-31G* and B3LYP/6-311++G** levels. For a complete assignment of the compound infrared spectrum, the DFT calculations were combined with Pulay's scaled quantum mechanical force field (SQMFF) methodology in order to fit the theoretical wavenumbers values to the experimental ones. The results were then used to predict the Raman spectra, for which there are no experimental data. An agreement between theoretical and available experimental results was found and a complete assignment of all the observed bands in the vibrational spectra was performed. The theoretical vibrational calculations allowed us to obtain a set of scaled force constants fitting the observed wavenumbers. Additionally, the frontier molecular HOMO and LUMO orbitals for the compound were analyzed and compared with those calculated for the 2-amino-1,3,4 thiadiazole molecule. The calculated H-1, C-13 and F-19 chemicals shifts are in good agreement with the corresponding experimental NMR spectra of the compound in solution.

• 出版日期2013-5-1