Use of vibrational spectroscopy to study 4-benzyl-3-(thiophen-2-yl)-4,5-dihydro-1H-1,2,4-triazole-5-thione: A combined theoretical and experimental approach Yusuf Sert a,b,⇑ , Ali A. El-Emam c , Ebtehal S. Al-Abdullah c , Abdul-Malek S. Al-Tamimi d , Çag ˘rı Çırak e , Fatih Ucun f a Department of Physics, Faculty of Art & Sciences, Bozok University, Yozgat 66100, Turkey b Sorgun Vocational School, Bozok University, Yozgat 66100, Turkey c Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia d Department of Pharmaceutical Chemistry, College of Pharmacy, Salman bin Abdulaziz University, Alkharj 11942, Saudi Arabia e Department of Physics, Faculty of Art & Sciences, Erzincan University, Erzincan 24100, Turkey f Department of Physics, Faculty of Art & Sciences, Süleyman Demirel University, Isparta 32100, Turkey highlights  The FT-IR and Laser-Raman spectra of the title compound were recorded in solid phase.  The optimized geometry and vibrational frequencies were calculated for the first time.  The HOMO–LUMO energies and related molecular properties were evaluated. graphical abstract article info Article history: Received 29 November 2013 Received in revised form 21 January 2014 Accepted 27 January 2014 Available online 12 February 2014 Keywords: FT-IR spectra Laser-Raman spectra Vibrational study 1,2,4-Triazole abstract In this study, the experimental and theoretical vibrational frequencies of a newly synthesized potential anti-inflammatory agent namely, 4-benzyl-3-(thiophen-2-yl)-4,5-dihydro-1H-1,2,4-triazole-5-thione have been investigated. The experimental FT-IR (4000–400 cm 1 ) and Laser-Raman spectra (4000– 100 cm 1 ) of the molecule in solid phase have been recorded. The theoretical vibrational frequencies and the optimized geometric parameters (bond lengths, bond angles and dihedral angles) have been cal- culated using density functional theory methods (DFT/B3LYP: Becke, 3-parameter, Lee–Yang–Parr and DFT/M06-2X: the highly parameterized, empirical exchange correlation function) with 6-311++G(d,p) basis set by Gaussian 09W software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis using VEDA 4 software program. The theoretical optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data and results in the literature. In addition, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy and http://dx.doi.org/10.1016/j.saa.2014.01.142 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Department of Physics, Faculty of Art & Sciences, Bozok University, Yozgat 66100, Turkey. Tel.: +90 354 2421021; fax: +90 354 2421022. E-mail address: yusufsert1984@gmail.com (Y. Sert). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 126 (2014) 280–290 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa