Synthesis, crystal structure, linear properties and DFT analysis of L-Tartarate hydrogen squarate (LTS): A nonlinear optical single crystal

Abstract

A novel organic non-linear single crystal of L-Tartarate hydrogen squarate (LTS) has been synthesized and successfully grown from aqueous solution by slow evaporation solution growth method. In the present investigation the title compound of L-Tartaric acid with squaric acid has been synthesized by using double distilled water as the solvent. The prepared concentrated solution was placed in an undisturbed condition and then the solution was periodically inspected. The good quality single crystals have been harvested in a time span of 40 days. Then the grown crystal was characterized by single crystal XRD, FTIR, UV–vis-NIR, and SHG. The optimized geometry, vibrational frequencies, Mulliken charge distribution, frontier molecular orbitals (FMOs), and associated energies of the ground state and the first single excited state were calculated using density functional theory (DFT) and time-dependant DFT calculations using the B3LYP/6- 311G method. Vibrational frequencies calculated in the gaseous phase compared with experimental values measured in the solid state and showed good agreement with each other. The observed results from the characterization analyses show its suitability for NLO applications when compared with some of the existing organic crystals. The relative second harmonic generation of this grown crystal was found to be 0.9 times than that of KDP crystal.