Growth and physical characterization of organic nonlinear optical single crystal: N,N′-diphenylguanidinium formate

A second-harmonic generation (SHG) crystal N,N'-diphenylguanidinium formate (DPGF) with good quality was successfully grown by the slow evaporation method. Single crystal X-ray diffraction study confirms that the DPGF crystallizes in orthorhombic crystal system with space group P2(1)cn. The powder XRD pattern shows the various planes of DPGF crystal. The H-1 and C-13 NMR spectral studies further confirm the molecular structure of the grown crystal. The various functional groups present in the grown crystal have been identified by Fourier transform infrared spectroscopy. The UV-vis-NIR spectrum was recorded to find the optical transmittance window, lower cut off wavelength and band gap of the DPGF crystal. Photoluminescence spectrum shows broad emission peak observed at 367 nm. Thermal stability of the title crystal was evaluated by thermogravimetric (TG) and differential thermal analysis. Wicker's microhardness study was carried out to reveal the mechanical properties of the grown crystal. The second harmonic conversion efficiency of DPGF crystal was 1.8 times than that of KDP crystal. Gaussian 03 W program has been used to calculate the molecular orbital and first order hyperpolarizability of the molecule. The calculated first order hyperpolarizability value of DPGF is found to be 16 times greater than that of urea.