Growth and Characterization of a Nonlinear Optical Crystal a Complex Orthonitroaniline with Picric Acid Single Crystal by Vertical Bridgman Technique

Abstract

International audienceSingle crystal of organic NLO material Orthonitroaniline with picric acid (2[C6H6N2O2]-C6H2(NO2)3OH) (ONAP) of dimensions 27mm length and 12mm of diameter was grown from melt using vertical Bridgman technique. The grown crystal was confirmed with monoclinic structure by single crystal X-ray diffraction studies. Fourier transform infrared spectroscopy was used to assign various modes and to identify the functional groups present in the crystal. The presence of title compound was confirmed by NMR studies. The suitability for laser applications for the reported crystal was confirmed with UV-Vis studies. Introduction. Organic crystals have been recognized as the materials of the future, due to their molecular nature, added with the versatility of synthetic chemistry helpful in changing and control their molecular structure, leading to the betterment of NLO properties [1]. The second order nonlinear optical material properties of the molecules are highly studied for potential applications, such as optical signal processing and optoelectronics [2]. Some crystals are highly polar due to their non-centro symmetric crystal nature, photonic crystals having band gap in the visible range are not noticed and is linked with some properties like refractive index, symmetry of the crystal and lattice spacing [3]. The grown crystal ONAP is easily polarisable based on the intermolecular properties. One of the important reasons for the selection of present compound is its inter molecular interaction between the pairs of orthonitroaniline and that of picric acid is well established that picric acid forms crystalline picrates with many organic molecules [3].and also a bulk size crystal is aimed to grow in this technique. The present crystal's melting point was reported to be 80 ̊ C [3] and it was found to be monoclinic crystal system having space group Cc [4]. For few organic materials solution growth methods are not good because of solvent or compound associations forming during the crystal growth and solvent inclusions can reduce the optical quality. Melt growth techniques are rapid and suitable for growing organic crystals [5]. The vertical Bridgman technique is simple and is the best technique for the growth of good organic and inorganic crystals in a limited period. The single wall ampoule with conical tip is very useful to grow good quality transparent crystals. In the present work Orthonitroaniline with picric acid (2[C6H6N2O2]-C6H2(NO2)3OH) (ONAP) single crystal was grown using the single wall ampoule by the vertical Bridgman technique