Molecular structure and vibrational spectroscopic studies of prothionamide by density functional theory

• The most stable conformer of PTH was obtained by PES scan.
• FT-Mid IR, FT-Far IR and FT-Raman spectroscopy investigation have been carried out.
• The anharmonic and harmonic wavenumbers were calculated.
• The normal coordinate analysis was utilized.
• HOMO–LUMO, NBO and ELF basin analyses were performed.

Prothionamide (PTH) is the secondary drug used against Mycobacterium tuberculosis bacteria and leprosy. The aim of this work was to investigate the potential energy surface map, anharmonic and harmonic vibrational spectra, NBO analysis and ELF (Electron Localization Function) of the title compound using DFT approach with the B3LYP (Becke, three-parameter, Lee–Yang–Parr) exchange–correlation functional with the 6-31G++(d, p) and the Z3POLX basis sets were employed. In the experimental part of this study, FT-Mid IR, FT-Far IR and FT-Raman spectra of the molecule were recorded in the regions 4000–450 cm−1, 700–30 cm−1 and 4000–100 cm−1 respectively in the solid phase. The comparison between calculated and experimental vibrational spectra (infrared and Raman spectra) and assignments of fundamental vibrational modes were characterized by total energy distribution (TED). Theoretical spectra were seen to be in good agreement with those of the experimental ones.

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