K. Gayathri

Studies on crystal growth, vibrational, optical, thermal and dielectric properties of new organic nonlinear optical crystal: Bis (2,3-dimethoxy-10-oxostrychnidinium) phthalate nonahydrate single crystal.

In this paper, we report the synthesis, growth and characterization of a new organic NLO single crystal of Bis (2,3-dimethoxy-10-oxostrychnidinium) phthalate nonahydrate, for the first time. The single crystal XRD study reveals that the crystal belongs to monoclinic system. The molecular structure and the nature of the vibrations were identified by vibrational and NMR spectroscopic studies. The UV absorption edge was found to be 330nm with a wide optical transmittance window covering the visible region. The crystal exhibits physicochemical stability upto 90.56°C. Various thermodynamic parameters were calculated from the TG data. The Kurtz powder second harmonic generation revealed that the SHG efficiency of the grown crystal was about 2.8 times that of KDP and was found to be phase matchable. The measured low value of birefringence indicates its suitability for NLO devices. The PL spectrum exhibited two peaks (355 and 406nm) due to the donation of protons from carboxylic acid to quartenium nitrogen. The dielectric behavior of the grown crystal was analyzed for different frequencies at different temperatures.

Growth, spectral, thermal, dielectric, mechanical, linear and nonlinear optical, birefringence, laser damage threshold studies of semi-organic crystal: Dibrucinium sulfate heptahydrate

Dibrucinium sulfate heptahydrate (DBSH), a semi-organic nonlinear optical material, has been synthesized and single crystals were grown from water-ethanol solution at room temperature up to dimensions of 10×7×2 mm(3). The unit cell parameters were determined from single crystal and powder X-ray diffraction studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) study. FTIR and Raman studies were performed to identify the functional groups present in the title compound. The activation energy (E), entropy (ΔS), enthalpy (ΔH) and Gibbs free energy (ΔG), of the thermal decomposition reaction have been derived from thermo gravimetric (TGA) and differential thermal (DTA) analysis curves, using Coats-Redfern method. The variation of dielectric properties of the grown crystal with respect to frequency has been investigated at different temperatures. Microhardness measurements revealed the mechanical strength of grown crystal. The optical parameters, the optical band gap E(g) and width of localized states Eu were determined using the transmittance data in the spectral range 200-800 nm. The relative second harmonic efficiency of the compound is found to be 1.4 times greater than that of KDP. Birefringence and Laser damage threshold studies were carried out for the grown crystal.

Growth and characterization of Melaminium bis (trichloroacetate) dihydrate.

Single crystals of melaminium bis (trichloroacetate) dihydrate have been grown successfully by slow evaporation solution growth technique at room temperature. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in monoclinic system with non -centrosymmetric space group C2 with lattice parameters a=17.70 Å, b=8.44 Å, c=6.09 Å, α=90°, β=100.24°, γ=90° and V=900 (Å)3. The UV-Vis transmittance spectrum shows that the crystal has a good optical transmittance in the entire visible region with lower cutoff wavelength of 351 nm. The vibrational frequencies of various functional groups present in the crystal have been derived from FI-IR, FT-Raman and Confocal Raman analyses. The chemical structure of the compound was established by 1H and 13C NMR spectrum. TGA-DTA analysis reveals that the materials have good thermal stability and the melting point of the crystal is found to be 195°C. The dielectric response of the crystals was studied in the frequency range 50 Hz to 5 MHz at different temperatures and the results are discussed. Etching studies show the growth pattern of the crystals. The second harmonic generation efficiency was measured in comparison with KDP by employing powder Kurtz method.

Growth, nonlinear optical, thermal, dielectric and laser damage threshold studies of semiorganic crystal: Monohydrate piperazine hydrogen phosphate

Monohydrate piperazine hydrogen phosphate (MPHP), a semi organic nonlinear optical material has been synthesized and single crystals were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction study on grown crystal reveals that they belong to monoclinic crystal system with space group P2(1)/c; (a=6.39Å; b=12.22Å; c=11.16Å; β=97.14°; V=864Å(3)). The structural perfection of the grown crystal was analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. FTIR spectrum confirms the presence of the functional groups in synthesized material. UV-Vis spectrum indicates that the crystal is transparent in the entire visible region with a lower cut off wavelength of 387 nm. The variation of dielectric properties of the grown crystal with respect to frequency has been investigated at different temperatures. Thermal analysis carried out on the MPHP crystal shows that the crystal is stable up to 135°C. Relative powder second harmonic generation efficiency tested by Kurtz-Perry powder technique, which was about 0.638 times that of Potassium dihydrogen phosphate.

Growth, optical, thermal and mechanical characterization of an organic crystal: Brucinium 5-sulfosalicylate trihydrate

Single crystals of Brucinium 5-sulfosalicylate trihydrate (B5ST) were grown from ethanol–water (1:1) mixed solvent by the slow solvent evaporation method. X-ray powder diffraction analysis reveals that the crystal belongs to orthorhombic system with space group P212121. The various reflections were indexed and the lattice parameters were calculated. Photoluminescence (PL) shows peaks corresponding to protonation of the amino group. The optical absorption spectrum shows that the crystal has 90% transmittance in the visible region with a lower cut-off wavelength of 312 nm. Thermal analysis performed on the grown crystal indicates the thermal stability of the crystal and various thermodynamical parameters were calculated from the thermogravimetry (TG) data. The mechanical properties like Vickers microhardness number (Hv), stiffness constant (C11) and yield strength (σv) of the crystal were estimated by Vickers hardness test.

Bis(2,3-dimeth-oxy-10-oxostrychni-din-ium) phthalate nonahydrate.

The asymmetric unit of the title compound 2C23H27N2O4 +·C8H4O4 2−·9H2O, contains a cation, an anionon a twofold axis and four and half molecules of water, one of which is located on the twofold axis. In the cation, both fused pyrrolidine rings exhibit twisted conformations, while the piperidine rings adopt screw–boat and boat conformations. In the crystal, the components are linked by N—H⋯O and O—H⋯O hydrogen bonds. The brucinium cations form typical undulating head-to-tail ribbon structuresalong the a-axis direction, which associate with the carboxy phthalate and the water molecules.

2,3-Dimeth-oxy-10-oxostrychnidinium hydrogen oxalate dihydrate.

In the cation of the title salt, C23H27N2O4 +·C2HO4 −·2H2O, both fused pyrrolidine rings exhibit twisted conformations, while the piperidine rings adopt screw-boat and boat conformations. In the crystal, the three components are linked via O—H⋯O and N—H⋯O interactions, forming a tape along the b axis. The tapes are further linked by weak C—H⋯O hydrogen bonds. forming a three-dimensional network.