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L-histidinium hydrogen oxalate (L-HisH)(HC2O4) crystal is formed from amino acid. L-histidine with oxalic acid whose vibrational high pressures behavior have not yet been investigated in the literature. Here we synthesized (L-HisH)(HC2O4) crystal by slow solvent evaporation method in a 1:1 ratio of L-histidine and oxalic acid. In addition, a vibrational study of (L-HisH)(HC2O4) crystal as a function of pressure was performed via Raman spectroscopy in the pressure range of 0.0-7.3 GPa. From analysis of the behavior of the bands within 1.5-2.8 GPa, characterized by the disappearance of lattice modes, the occurrence of a conformational phase transition was noted. A second phase transition, now from structural type, close to 5.1 GPa was observed due to the incidence of considerable changes in lattice and internal modes, mainly in vibrational modes related to imidazole ring motions.

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Raman spectroscopy and synchrotron radiation X-ray diffraction have been used to study the effect of pressure on 2-(-α-methylbenzylamino)-5-dinitropyridine (MBANP). Several changes are observed with increasing pressure in the Raman spectra of this system, such as splitting of various bands and disappearance of bands. Discontinuous shifts in wavenumber vs pressure plot indicate that a conformational phase transition takes place around 0.5 GPa. The behavior of the Raman spectra indicates that MBANP molecules present conformational phase transition at high-pressure. X-ray diffraction, performed with synchrotron radiation, confirms the conformational changes observed by Raman experiments around 0.5 GPa. The pressure provokes a rotational movement of the benzene ring which can be associated with the conformational phase transition.

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Tris(glycinato)chromium(III) monohydrate [Cr(C2H4NO2)3·H2O] crystals were grown through the slow solvent evaporation method. The crystals were studied by Fourier transform infrared (FTIR) and Raman spectroscopy at room temperature. The assignments of vibration modes were performed using the Density Functional Theory (DFT). Thermal analyses (TGA, DTA, and DSC), X-ray diffraction (XRD), and Raman were used to study the phase changes on the crystals under high- and low-temperature conditions. Temperature-dependent XRPD measurements were carried out in the interval of 473-12 K. Several changes were observed in the patterns, like the appearance of new peaks and the disappearance of peaks occurring within 373-393 K due to water loss. In addition, the Raman measurements were performed in the 423-10 K interval. Several changes on the inter and intramolecular vibration bands during the cooling, such as decreasing bands' intensities, the appearance of vibration modes, and discontinuities on the modes' behavior, were observed. These spectral modifications occurred at about 370 K and within 120-220 K, thus, confirming that the crystals undergo two phase changes, one being structural and the other one conformational, respectively, at high- temperature and low-temperature conditions. Finally, thermal investigations corroborated the structural and vibrational results under high temperatures.

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Chloro(glycinato-N,O)(1,10-phenanthroline-N,N')­copper(II) trihydrate complex was synthesized through the slow evaporation method. The crystal's structural, thermal, magnetic, and vibrational properties were obtained by X-ray powder diffraction (XRPD), thermal analyses, magnetization, Raman, and Fourier-transform infrared (FT-IR) spectroscopy. XRPD results showed that the crystalline complex belongs to a monoclinic system (P21/n). Thermal analyses revealed that around 333 K, the material undergoes a thermodynamically irreversible process. Magnetic data showed a paramagnetic behavior with weak ferromagnetic interactions. Moreover, all the Raman- and infrared-active bands were assigned from computational calculations based on the density functional theory (DFT) to analyze intra-molecular vibrational modes. In addition, the cytotoxic assay on colorectal cancer cells was performed to evaluate the antitumor activity of this ternary compound. Therefore, the antineoplastic activity of [Cu(1,10-phenanthroline)(glycine)Cl]•3H2O complex in HCT-116 cells was confirmed, showing a potent cytotoxic effect.

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DL-glutamic acid monohydrate crystal was synthesized from an aqueous solution by slow evaporation technique. The crystal was submitted to high-pressure (1 atm-14.3 GPa) to investigate its vibrational behavior and the occurrence of phase transitions. We performed Raman spectroscopy as probe and through the analysis of the spectra we discovered three structural phase transitions. The first one occurs around 0.9 GPa. In this phase transition, glutamic acid molecules suffer modifications in their conformations while water molecules are less affected. The second phase transition at 4.8 GPa involves conformational changes related to CO2-, NH3+ units and the water molecules, while the third one, between 10.9 and 12.4 GPa, involves motions of several parts of the glutamic acid as well as the water molecules. Considering the dynamic of high pressure, the second phase of DL-glutamic acid monohydrate crystal presented a better stability compared with the second phase of its polymorphs α and ß L-glutamic acid. In addition, water molecules seem to play important role on this structural stability. All changes are reversible.

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The study of [bis(L­alaninato) diaqua] nickel(II) dihydrate crystal using Raman scattering and X-ray diffraction as a function of temperature is reported in this paper. Thermal analysis (TGA and DSC) complementary measurements were also performed in order to obtain information on structural changes and mass loss occurred in this material. It was identified that the crystal undergoes loss of water at two different temperatures: ~340 and 393 K. X-ray diffraction measurements showed two phase transformations related to these two water loss events. After heating up to 423 K, the sample was cooled down to 298 K and its diffraction pattern presented the same pattern at 423 K, evidencing an irreversible phase transformation. The diffraction results also showed that crystal goes to monohydrate and anhydrous phases. Furthermore, cell lattice parameters and space groups of both phases were determined by applying Rietveld refinement through Le Bail method, demonstrating that their structures belong to the P21 and C2/c space groups, both with monoclinic symmetry. In addition, assignments of Raman spectra vibrational bands (at 300 K) are provided. The high-temperature Raman spectra were obtained in the 100-3500 cm-1 range, where it was observed several abrupt changes in the intensity of low-wavenumber bands and the appearance/disappearance of some vibrational modes that have coupling with OH⋯O hydrogen bonds. These spectral changes are in good agreement with X-ray diffraction and thermal analyses data. Finally, we obtained Raman measurements at low temperatures, from which we identified that the crystal structure is extremely stable throughout the temperature range of 293-10 K.

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Single crystal of monoglycine nitrate has been studied by Raman spectroscopy under high pressures up to 5.5 GPa. The results show changes in lattice modes in the pressure ranges of 1.1-1.6 GPa and 4.0-4.6 GPa. The first change occurs with appearance of bands related to the lattice modes as well as discontinuity in the slope of dΩ/dP of these modes. Moreover, bands associated with the skeleton of glycine suggest that the molecule undergoes conformational modifications. The appearance of a strong band at 55 cm(-1) point to a second phase transition associated with the lattice modes, while the internal modes remain unchanged. These anomalies are probably due to rearrangement of hydrogen bonds. Additionally, decompression to ambient pressure shows that the phase transitions are reversible. Finally, the results show that the nitrate anions play an important role on the stability of the monoglycine nitrate crystal.

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Crystals of pure potassium dihydrogen phosphate KH(2)PO(4) (KDP) and Mn-doped KDP (KDP:Mn) were grown from a water solution by the slow evaporation method and their piezoelectric properties were studied by X-ray diffraction methods. The results have shown an increase in the piezoelectric coefficients with the doping.

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Magnetocaloric properties of antiferromagnetic RGa(2) (R = Ce, Pr, Nd, Dy, Ho and Er) compounds have been reported. These systems present an antiferromagnetic transition below 15 K and a field induced metamagnetic transition from the antiferromagnetic to ferromagnetic state. Our results show that the character of the magnetic field induced transition along the series affects the magnetocaloric properties. For the compounds with R = Ho, Dy and Er both negative and positive magnetocaloric effect (MCE) were observed above µ(0)ΔH = 2 T where the rate between negative and positive MCE contributions depends on how the magnetic transitions occur in these compounds. The evaluated values of maximum magnetocaloric properties of RGa(2) compounds are similar to other potential magnetic refrigerant materials reported in the literature.

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We report on pressure effects on the magnetic and magnetocaloric properties of the compound UGa(2). Using a mean field approximation, we were able to calculate the isothermal entropy change and the adiabatic temperature change. Neither the applied pressure nor the chemical substitution experiments within the ranges studied revealed a remarkable improvement on the magnetocaloric effect (MCE) except for the Al substitutions. Nevertheless, we found that mechanical pressure and chemical pressure are equivalent in terms of the Curie temperature shift when Al, Ge and Si are substituted for Ga, but a different behavior is found when Ni, Fe and Co are used. Our results also show that a composite to operate between 80 and 120 K can be obtained using different concentrations of U(Ga,Ni)(2).