Proceedings Article | 12 March 2020
KEYWORDS: Terahertz radiation, Terahertz spectroscopy, Spectroscopy, Molecular spectroscopy, Absorption spectroscopy
Sartans represent the most frequently prescribed antihypertensive agents, which exert their action by inhibiting the binding of angiotensin Ⅱ(AT), a blood pressure regulating agent to its AT receptor. Among them, olmesartan, irbesartan and candesartan are excellent AT receptor inhibitors, and their excellent properties are closely related to the representative molecular structures. There are five-membered nitrogen ring, carbonyl group (C=O) or carboxylic group (-COOH) in such three kinds of sartans, and different structures could be distinguished successfully with terahertz time domain spectroscopy (THz-TDS) due to the characteristics of finger-print features. In this work, the vibrational spectra of olmesartan, irbesartan and candesartan have been characterized by THz-TDS. Distinctive absorption peaks are observed at 0.52, 1.08, 1.36 THz for olmesartan, 0.65, 0.74, 1.09, 1.28 THz for irbesartan and 0.60, 1.47 THz for candesartan by THz-TDS measurement, respectively. Density functional theory (DFT) has been used to simulate three kinds of sartans. The theoretical simulation has predicted characteristic peaks of three sartans in the 0.2~1.6 THz range, and the absorption peaks have been simulated at 0.51, 0.71, 1.12, 1.30 THz for olmesartan, 1.05, 1.33 THz for irbesartan, 0.59, 1.53 THz for candesartan. In addition, the molecular structures of three kinds of sartans have also been analyzed. The simulated results were agreement with experimental results very well, and the vibrational modes of peaks were also assigned based on the simulated results of DFT calculation in this study.
