Investigation on Growth, Structural, Spectral, Optical, and Mechanical Properties of an Organic Nonlinear Optical Material: Morpholinium Hydrogen Tartrate
Organic nonlinear optical crystal morpholinium hydrogen tartrate (MHT), with molecular formula [C8H15NO7], has been grown by slow evaporation solution technique. Single crystal X-ray diffraction study confirms that MHT crystallizes in orthorhombic system with noncentrosymmetric space group P212121. FTIR spectrum was recorded to identify the various functional groups of MHT. The various kinds of protons and carbons of MHT have been identified using 1H and 13C NMR spectral analyses. The range of optical absorption was ascertained by recording UV-Vis-NIR spectral studies. The TG/DTA studies revealed that the grown crystal is thermally stable up to 159.26°C. The mechanical property of the grown crystal was studied using Vickers microhardness studies. The relative second harmonic generation efficiency of MHT was determined using Kurtz and Perry powder technique; it was observed to be greater than that of KDP crystal. 1. Introduction In recent years, organic nonlinear optical crystals have been greatly investigated due to their high nonlinearities and rapid response in electrooptic effect compared to inorganic materials. The organic nonlinear optical crystals provide the key functions of frequency conversion, optical switching, telecommunication, colour display, and second harmonic generation. Within the last few years, much progress has been made in the development of nonlinear optical organic materials for second harmonic generation. However, most of the organic NLO crystals are constituted by weak van der Waals and hydrogen bonds with conjugated π electrons [1]. Morpholine is a strong alkali, which can be considered as a kind of secondary aliphatic amine. However, the incorporation of nitrogen into the six-member ring exposes the lone electron pair on nitrogen and makes the molecule as a good nucleophile. Morpholine and its derivatives are known to form a series of molecular complexes such as morpholine [2], hydrohalides [3], phenols [4], and phosphoric acid [5]. Recently, the structure and various characterizations of nonlinear optical crystal of morpholinium 4-aminobenzoate have been reported [6]. The crystal structure of morpholinium hydrogen tartrate was reported by Liu [7], but there are no reports available on the growth and other characterizations of morpholinium hydrogen tartrate. The crystal complex was formed by the transformation of one proton of the L-tartaric acid to the nitrogen atom of morpholine. In the present investigation, crystal growth, structural, spectral, optical, thermal, and mechanical properties of morpholinium hydrogen tartrate,
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