Crystal structure, spectroscopic, electronic, luminescent and nonlinear optical properties of (S)-4-Amino-5-(1-hydroxy-ethyl)-2,4-dihydro-[1,2,4]triazole-3-thione: A combined experimental and DFT study

4-Amino-5-(1-hydroxy-ethyl)-2,4-dihydro-[1,2,4]triazole-3-thione was synthesized and characterized by single crystal x-ray analysis. Thermodynamic calculations at B3LYP/6-31+G(d,p) level of theory proved that 4-Amino-5-(1-hydroxy-ethyl)-2,4-dihydro-[1,2,4]triazole-3-thione is the most stable tautomer in comparison with (S)-1-(4-Amino-5-mercapto-4H-[1,2,4]triazol-3-yl)-ethanol and (S)-4-Amino-5-(1-hydroxy-ethyl)-4,5-dihydro-[1,2,4] triazole-3-thione respectively. The title compound has been analyzed for its photophysical properties through vibration, absorption and photoluminescence spectroscopy. Theoretical calculations of the title compound were performed at B3LYP/6-31+G(d,p) level of theory in order to gain insight into the geometric, electronic and non-linear optical properties. Theoretical 1H and 13C NMR spectra calculated through GIAO formalism at B3LYP/6-311+G(2d,p) level in DMSO solvent showed excellent correlation with the experimental spectra. The experimental solid state photoluminescence spectrum was studied for the title compound. NBO charge analysis has also been performed to study charge transfer. Nonlinear optical properties analysis of the title compound reveals that the first static hyperpolarizability of 4-Amino-5-(1-hydroxy-ethyl)-2,4-dihydro-[1,2,4]triazole-3-thione is 9 times higher than urea (a commercial NLO material).