Synthesis, experimental, theoretical characterization and biological activities 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 (III) by quantum chemical calculations and spectral techniques. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of III 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.

6-Phenyl-3-(4-pyridyl)-1,2,4-triazolo-[3,4-b][1,3,4]thiadiazole: synthesis, experimental, theoretical characterization and biological activities.

The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional theory (DFT) methods with 6-31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and (1)H and (13)C NMR chemical shift values show good agreement with experimental data. To determine conformational flexibility, molecular energy profile of the title compound was obtained by HF/6-31G(d) and (DFT/B3LYP) calculations with respect to selected degree of torsional freedom, which was varied from -180° to +180° in steps of 10°.