Synthesis, growth, characterization and quantum chemical investigations of a promising organic nonlinear optical material: Thiourea-glutaric acid

Abstract

A promising organic nonlinear optical (NLO) material of thiourea-glutaric acid (TG) has been synthesized and its single crystals were grown by a conventional slow evaporation method. The molecular structure of TG was explored by (1H and 13C) NMR spectral and single crystal X-ray diffraction (SCXRD) techniques. The vibrational modes of functional groups involved in TG crystal were ascertained profoundly using FTIR and FT-Raman spectroscopic techniques. The grown crystal exhibited a high optical transmittance of 65% within the range of 226–1100 nm. Thermal stability was determined as 236 °C for TG crystal using thermogravimetric/differential thermal analysis (TG/DTA) and differential scanning calorimetric (DSC). Second harmonic efficiency (SHG) of TG was about 6.2 times higher than the standard KDP crystal. The surface of TG crystal showed high tolerance to the laser power with the threshold value of 3.5 GW/cm2. The dielectric study revealed that grown TG crystal showed a low dielectric constant (ɛr = 18) and a low dielectric loss values at higher frequencies. The mechanical and photoconducting behaviours of TG crystal were studied intensely. Furthermore, density functional theory (DFT) calculations such as Mulliken atomic charge distribution, frontier molecular orbital (FMOs), molecular electrostatic potential map analysis and NLO calculations were carried out.