Article,
Pressure-induced phase transitions in DL-glutamic acid monohydrate crystal
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, (2020)
DOI: 10.1016/j.saa.2020.118059
Abstract
DL-glutamic acid monohydrate crystal was synthesized from an aqueous
solution by slow evaporation technique. The crystal was submitted to
high-pressure (1 atm-143 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 ocatrs 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 DLglutamic acid monohydrate crystal
presented a better stability compared with the second phase of its
polymorphs alpha and beta L-glutamic add. In addition, water molecules
seem to play important role on this structural stability. All changes
are reversible. (C) 2020 Elsevier B.V. All rights reserved.
