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Pressure-induced phase transitions in DL-glutamic acid monohydrate crystal.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy ( IF 4.3 ) Pub Date : 2020-01-10 , DOI: 10.1016/j.saa.2020.118059
F M S Victor 1 , F S C Rêgo 2 , F M de Paiva 3 , A O Dos Santos 1 , A Polian 4 , P T C Freire 2 , J A Lima 2 , P F Façanha Filho 1
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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 β L-glutamic acid. In addition, water molecules seem to play important role on this structural stability. All changes are reversible.

中文翻译:

DL-谷氨酸一水合物晶体中压力诱导的相变。

通过缓慢蒸发技术由水溶液合成DL-谷氨酸一水合物晶体。将晶体置于高压下(1 atm-14.3 GPa),以研究其振动行为和相变的发生。我们以拉曼光谱为探针,通过对光谱的分析,我们发现了三个结构相变。第一个发生在0.9 GPa左右。在该相变中,谷氨酸分子的构象受到修饰,而水分子的影响较小。4.8 GPa的第二个相变涉及与CO2-,NH3 +单元和水分子有关的构象变化,而第三个相变(介于10.9和12.4 GPa之间)涉及谷氨酸的几个部分以及水分子的运动。考虑到高压的动态,与多晶型物α和βL-谷氨酸的第二相相比,DL-谷氨酸一水合物晶体的第二相具有更好的稳定性。另外,水分子似乎对该结构稳定性起重要作用。所有更改都是可逆的。
更新日期:2020-01-11
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