Abstract
2,3‐Diaryl‐tetrazole‐5‐thione (diaryl=diphenyl, di(p‐methylphenyl) and di(p‐chlorophenyl)) has been synthesized and characterized by elemental analysis, IR and electronic absorption spectroscopy. Two of them have also been characterized by X‐ray diffraction analysis. Density functional theory calculations of the structures, charge distribution, natural bond orbital and topological analysis of the three compounds were performed at B3LYP/6‐31G* level. The calculational results are in good agreement with the X‐ray data and show that different substitute group results in different charge distribution, the exocyclic sulfur atom has the biggest negative charge value and this site is the most likely site of protonation and methylation as well as the potential coordination site with metallic ions. The predicted harmonic vibration frequencies were compared with the experimental values. On the basis of vibrational analyses, the thermodynamic properties of these compounds at different temperatures were calculated, which reveal that $ S^{0}_{\rm m} $, $ H^{0}_{\rm m} $ and temperatures have good linear correlations. The calculations of second order optical nonlinearity have also been carried out and relatively high molecular hyperpolarizability values of 1.0913×10^‐29^‐1.6518×10^‐29^ esu were predicted.