Study on terahertz spectra of benzimidazole molecular

Absorption spectra and refractive indices of benzimidazole molecules have been measured by terahertz time-domain spectroscopy (THz-TDS) in the room temperature and nitrogen conditions. We discussed the absorption spectra of thiabendazole and carbendazim in THz region. Meanwhile, density functional theory (DFT) with software package Gaussian 03 was employed for optimization and vibration analysis. The distinct absorption peaks of those molecules were caused by intermolecular hydrogen-bonding, molecular torsion or vibration modes, absorption of water molecules, etc. This result shows that the THz-TDS can be used for distinguishing between thiabendazole and carbendazim. As the absorption spectra are highly sensitive to the overall structure and configuration of the molecules, the THz-TDS procedure can provide a direct fingerprint of the molecular structure or conformational state of a compound.