Structural characterization and biological functions of 4-ethyl-5-(2-hydroxyphenyl)-2H-1,2,4-triazole-3(4H)-thione

This work presents the characterization of 4-Ethyl-5-(2-hydroxyphenyl)-2H-1,2,4-triazole-3(4H)-thione (I) by quantum chemical calculations and spectral techniques. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of I in the ground state have been calculated using the density functional method (B3LYP) with the 6−31G(d) basis set. The calculated results show that the optimized geometry can well reproduce the crystal structure, and the theoretical vibrational frequencies and chemical shift values show good agreement with experimental values. To determine conformational flexibility, the molecular energy profile of the title compound was obtained by DFT calculations with respect to the selected torsion angle, which was varied from −180° to +180° in steps of 10°. The energetic behavior of I in solvent media was examined using the B3LYP method with the 6−31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The predicted non-linear optical properties of I are greater than ones of urea. In addition, DFT calculations of molecular electrostatic potentials and frontier molecular orbitals of I were carried out at the B3LYP/6−31G(d) level of theory. The title compound was screened for antibacterial, antifungal and antioxidant activities.