Experimental and theoretical study on 3-benzyl-4-phenyl-1,2,4-triazole-5-thione

The 3-benzyl-4-phenyl-1,2,4-triazole-5-thione was synthesized and examined by elementary analysis, IR and electronic spectra. Density functional theory calculations of the structure, natural bond orbitals and thermodynamic functions of the title compound were performed at B3LYP/6-311G** level of theory. Vibrational frequencies were predicted, assigned and compared with the experimental data, and they are supported by the experimental data. Electronic absorption spectra were calculated by the time-dependent density functional theory (TD-DFT), which indicates that the two absorption bands are mainly derived from the contribution of bands it pi ->pi*. The calculation of the second order optical nonlinearity was carried out, giving value of molecular hyperpolarizability equal to 4.025.10(-30) esu. These calculated results were also compared with results obtained for a similar molecule, 4-phenyl-3-[(1,2,4-triazol-1-yl)methyl]-triazole-5-thione, reported earlier by this group.