Crystal growth, physical properties, and theoretical investigation on organic acentric single crystal towards efficient second-order NLO applications: Triphenylguanidine

Abstract

A novel organic nonlinear optical crystal Triphenylguanidine (TPG) was grown by the solvent evaporation method. Single-crystal X-ray diffraction (XRD) studies showed that the TPG compound crystallizes in orthorhombic crystal system with Pna21 space group and the corresponding lattice planes of reflections were indexed using powder XRD studies. Fourier transform infrared and Fourier transform Raman studies revealed the presence of various functional groups in the TPG crystal. The molecular structure of TPG was also confirmed using the NMR studies. UV–Vis studies validate the aptness of TPG crystal towards nonlinear optical applications. TPG crystal shows blue emission from photoluminescence studies. The mechanical stability of the grown crystal was identified using Vickers microhardness studies. Dielectric studies were carried out as a function of frequency at room temperature. Powder SHG effective nonlinearity of TPG crystal is about 2.3 times that of standard KDP. The thermal stability of TPG crystal was investigated by the TG-DTA studies. Using Gaussian 03 program the HOMO–LUMO energy gap and first-order hyperpolarizability value for TPG molecule were calculated. The calculated first-order hyperpolarizability value of TPG molecule is 17 times that of urea.