Growth and characterization of urea-thiourea non-linear optical organic mixed crystal

264-270Mixed crystals of urea-thiourea in various proportions have been grown in solution by slow evaporation technique at room temperature (30°C). The solubility studies have been carried out at room temperature. In the presence of high concentrations of the thiourea in the medium, the solubility decreases appreciably. X-ray diffraction study has been carried out to find the crystal system and unit cell parameters. The diffraction patterns reveal that there is change in basic structure of urea and thiourea. The presence of title compound in the crystal lattice has been qualitatively determined by FTIR analysis. Slight broadening is observed in FTIR of 0.66 and 0.9 urea-thiourea mixed crystal in the range 3500-3300 cm-1. It is found that weak hydrogen bond between urea and thiourea is present in higher proportions of urea-thiourea mixed crystal

Crystal growth, structure, crystalline perfection and characterization of zinc magnesium ammonium sulfate hexahydrate mixed crystals ZnxMg(1-x)(NH4)(2)(SO4)(2) center dot 6H(2)O

Mixed crystals ZnxMg(1-x)(NH4)(2)(SO4)(2) center dot 6H(2)O of the two well-known Tutton's salts Zn(NH4)(2)(SO4)(2) center dot 6H(2)O and Mg(NH4)(2)(SO4)(2) center dot 6H(2)O were grown with varying molar proportions (x=0.10-0.90) by slow evaporation solution growth technique. The mixed crystal Zn0.54Mg0.46(NH4)(2)(SO4)(2) center dot 6H(2)O is crystallizing in monoclinic system with space group P2(1)/c and cell parameters a=6.2217(4) angstrom, b=12.5343(7) angstrom, c=9.2557(6) angstrom, beta=106.912(3)degrees. The coexistence of zinc and magnesium ions in the mixed crystal was confirmed by inductively coupled plasma (ICP), atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS). Compositional dependence of lattice parameters follows Vegard's relations. Slight variations are observed in FT-IR and XRD of pure and mixed crystals. Comparison of crystalline perfection as evaluated by high-resolution X-ray diffraction (HRXRD) for mixed crystals of various proportions reveals a reasonably good crystalline perfection for the mixed crystal with nearly equimolar ratio of Zn and Mg. The surface morphology of the mixed crystals changing with composition was studied by scanning electron microscopy (SEM). UV-vis studies reveal that the transparency of the mixed crystals was not much affected

TG, DTA, FTIR and raman spectral analysis of Zna/Mgb ammonium sulfate mixed crystals

To understand the structural and thermal properties of the mixed crystals, thermogravimetric (TG) and differential thermal analysis (DTA), and FTIR and Raman spectral studies were carried out for the mixed crystals of Zna/Mgb ammonium sulfate of composition namely ?a' (fraction by weight of salt Zn[NH4]2[SO4]2.6H2O to the total salt (both Zn[NH4]2[SO4]2.6H2O, Mg[NH4]2[SO4]2.6H2O or it can be explained as ZnaMgb[NH4]2[SO4]2.6H2O, a + b =1), and a = 0.1, 0.25, 0.333, 0.5, 0.666, 0.75 and 0.9 grown by a solution technique. From the correlation and analysis of the results obtained for the various crystals, the desolvation, decomposition, crystalline transition phenomena were identified. By close comparison of the endotherms, obtained for the various crystals, it was found that isomorphous substitution takes place in the crystals. Up to 0.5, Zn2+ ion replaces isomorphous Mg2+ ions in the lattice sites of Mg[NH4]2[SO4]2.6H2O and above 0.5, Mg2+ ions occupies the Zn2+ ion in the lattice sites of Zn[NH4]2[SO4]2.6H2O. Both crystals belong to monoclinic system with P 2(1)/a symmetry. The vibrations of NH4+ ion, SO42- ion, the complex [Mg(OH2)6]2+ the complex [Zn(OH2)6]2+ and thethree different water molecules are identified. The linear distortion of SO42- ion is found to be greater than its angular distortion, while the NH4+ ion has suffered more angular distortion. The possibility of free rotation of the NH4+ ion is ruled out.Afin de comprendre les propri\ue9t\ue9s structurales et thermiques des cristaux mixtes, on a r\ue9alis\ue9 des analyses thermogravim\ue9triques (TG) et des analyses thermiques diff\ue9rentielles (ATD), ainsi que des \ue9tudes de spectrom\ue9trie infrarouge \ue0 transform\ue9e de Fourier et des \ue9tudes de spectrom\ue9trie Raman, pour les cristaux mixtes de sulfate d?ammonium Zna/Mgb, \ue0 savoir de composition a? (fraction massique de sel Zn[NH4]2[SO4]2.6H2O au sel total (Zn[NH4]2[SO4]2.6H2O et Mg[NH4]2[SO4]2.6H2O, ou on peut l?expliquer comme ZnaMgb[NH4]2[SO4]2.6H2O, a + b = 1), et a = 0,1, 0,25, 0,333, 0,5, 0,666, 0,75 et 0,9, obtenus par une solution de qualit\ue9 technique. \uc0 partir de la corr\ue9lation et de l?analyse des r\ue9sultats d\ue9gag\ue9s pour les divers cristaux, on a pu identifier les ph\ue9nom\ue8nes de d\ue9solvation, de d\ue9composition et de transition cristalline. En comparant de pr\ue8s les endothermes obtenus pour les divers cristaux, on a d\ue9couvert qu?il y avait substitution isomorphe dans ceux-ci. Jusqu?\ue0 0,5, l?ion Zn2+ remplace les ions isomorphes Mg2+ dans les sites de Mg[NH4]2[SO4]2.6H2O, et au del\ue0 de 0,5, les ions Mg2+ remplacent l?ion Zn2+ dans les sites de Zn[NH4]2[SO4]2.6H2O. L?un et l?autre cristaux appartiennent au syst\ue8me monoclinique avec sym\ue9trie P 2(1)/a. On a identifi\ue9 les vibrations de l?ion NH4+, de l?ion SO42-, le complexe [Mg(OH2)6]2+, le complexe [Zn(OH2)6]2+ et les trois (3) diff\ue9rentes mol\ue9cules d?eau. La distorsion lin\ue9aire de l?ion SO42- s?est r\ue9v\ue9l\ue9e sup\ue9rieure \ue0 sa distorsion angulaire, tandis que l?ion NH4+ a subi une distorsion angulaire plus accus\ue9e. La possibilit\ue9 d?une rotation libre de l?ion NH4+ est exclue.Peer reviewed: YesNRC publication: Ye

Synthesis of amine-phenol ligands in water – a simple demonstration of a hydrophobic effect

The synthesis in water of a series of tetradentate amine-phenol ligands derived from formaldehyde, 2,4-disubstituted phenols and amines is presented. These molecules, which are used in catalyst development, include 4,6-di-alkyl-2-bis(2-methoxyethyl)aminomethylphenols and 4,6-di-tert-amyl-2-bis(3-(dimethylamino)propyl)aminomethylphenols. Yields were generally greater than reactions performed in methanol and near quantitative for hydrophobic phenols

Polar Effects in Acid-Catalysed Decomposition of Potassium Alkylxantbates

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Thermal, Structural and Optical Analyses of Benzimidazole Single Crystal Grown with Organic Dopants for Nonlinear Optical Applications

Nowadays nonlinear optical (NLO) materials are gaining attention because of their numerous applications in the area of fibre optic communication and optical signal processing. In the present study, the nonlinear optical material of benzimidazole (BMZ) has been grown by slow evaporation solution growth technique using two different organic dopants (Urea and N-methyl urea) at different molar percentages. The effect of dopants on the growth and other physical properties has been analyzed by different instrumentation methods. The addition of urea and N-methyl urea (NMU) to the host material of benzimidazole has not changed the existing crystalline system, but there was a trivial variation in the lattice dimensions which is confirmed by powder X-ray diffraction analysis. The crystalline perfection was analyzed by high resolution X-ray diffraction analysis. It was found that urea dopant enhances the crystalline perfection in comparison with the N-methyl urea, which is in tune with the scanning electron microscopic analysis. The thermal performance has been examined by TG-DTA for all the doped specimens. Its relative second harmonic generation efficiency was evaluated by Kurtz powder technique and it was found that the doped specimens showed enhanced efficiency in comparison with the pure benzimidazole. Its optical properties have been examined by UV-VIS spectral analysis and found variations in the observed transmittance values were found

Influence of organic solvent on tristhioureazinc(II)sulphate crystals

It was observed that the addition of a very small quantity (5 center dot 10(-3) M L(-1)) of an organic solvent, benzene (C(6)H(6)) in the aqueous growth medium (pH similar to 5.9) of tristhioureazinc(II)sulphate (ZTS) markedly influences the SHG efficiency. The measurements using Nd:YAG laser source reveal that second harmonic generation (SHG) conversion efficiency which is one of the most important nonlinear optical (NLO) properties is enhanced by benzene dopant by a factor of nearly 1.5 times. The crystalline perfection of the grown crystals was evaluated by high-resolution X-ray diffractometry (HRXRD). The full width at half maximum (FWHM) of the diffraction curve (which gives an estimate for the degree of crystalline perfection) for undoped and benzene doped specimen crystals are 26 and 15 arc sec, respectively. The reduction in FWHM due to the benzene solvent indicates the significant improvement in crystalline perfection. This very much suggests that the dissolution of trace impurities in the presence of benzene prevents the entry of impurities into the crystal lattice and at the same time enhances the growth promoting effect (GPE). Not much variation is observed in XRD, FTIR and TG-DTA of ZTS in the presence and absence of benzene in the aqueous growth medium

Thermal and optical properties of ZTS single crystals in the presence of 1,10-phenanthroline (Phen)

The influence of heteroaromatic N-base (1,10-phenanthroline) (Phen), a new additive as complexing agent on tris(thiourea)zinc(II)sulphate (ZTS) crystals from aqueous solutions at 30 °C is investigated. Crystals were grown using low concentration of the dopant (0.005 M L−1) in the aqueous growth medium and the growth promoting effect (GPE) is much greater because of an increase in the metastable zone width. High dopant concentration decreases GPE. The crystalline perfection of the grown crystals is quite good both in doped and undoped crystals as evaluated by high-resolution X-ray diffractometry (HRXRD). The diffraction curve of a typical Phen doped as-grown ZTS crystal was observed to contain a single peak indicating that the crystal does not contain any epitaxial layer on the surface or internal structural grain boundaries. Not much variation is observed in FT-IR and XRD of pure and doped ZTS. Phen depresses the NLO efficiency of ZTS. It could be ascribed due to the disturbance of charge transfer in the presence of the dopant. The grown crystals were also characterized by UV–Vis, SEM and TG–DTA techniques