FT-Raman, FT-IR and UV–visible spectral investigations and ab initio computations of anti-epileptic drug: Vigabatrin

• DFT calculations have been performed on the anti-epileptic drug vigabatrin.
• The IR, Raman and UV–vis spectra of the compound were recorded.
• The computed and experimental wavenumbers have been compared.
• NBO, NHO, ESP, Mulliken analyses and HOMO–LUMO energy gap suggests bioactivity.

Vibrational analysis of anti-epileptic drug vigabatrin, a structural GABA analog was carried out using NIR FT-Raman and FTIR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational wavenumbers were studied using density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of VEDA.4 program. Vibrational spectra, natural bond orbital analysis and optimized molecular structure show clear evidence for the effect of electron charge transfer on the activity of the molecule. Predicted electronic absorption spectrum from TD-DFT calculation has been compared with the UV–vis spectrum. The Mulliken population analysis on atomic charges and the HOMO–LUMO energy were also calculated. Good consistency is found between the calculated results and experimental data for the electronic absorption as well as IR and Raman spectra. The blue-shifting of the CC stretching wavenumber reveals that the vinyl group is actively involved in the conjugation path. The NBO analysis confirms the occurrence of intramolecular hyperconjugative interactions resulting in ICT causing stabilization of the system.

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