Phase changes of tris(glycinato)chromium(III) monohydrate crystal systematically studied by thermal analyses, XRPD, FTIR, and Raman combined with ab initio calculations

J A O Rodrigues; J G Oliveira Neto; C C Santos; C E S Nogueira; F F de Sousa; A S de Menezes; A O Dos Santos

doi:10.1016/j.saa.2022.120883

Phase changes of tris(glycinato)chromium(III) monohydrate crystal systematically studied by thermal analyses, XRPD, FTIR, and Raman combined with ab initio calculations

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Apr 15:271:120883. doi: 10.1016/j.saa.2022.120883. Epub 2022 Jan 10.

Authors

J A O Rodrigues¹, J G Oliveira Neto¹, C C Santos², C E S Nogueira³, F F de Sousa⁴, A S de Menezes⁵, A O Dos Santos¹

Affiliations

¹ Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal do Maranhão, CCSST, Imperatriz, MA 65900-410, Brazil.
² Departamento de Física, Universidade Federal do Maranhão, CCET, São Luís, MA 65080-805, Brazil.
³ Universidade Regional da Cariri, Crato, CE 63010-970, Brazil.
⁴ Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal do Maranhão, CCSST, Imperatriz, MA 65900-410, Brazil; Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, 66075-110 Belém, PA, Brazil. Electronic address: ffs@ufpa.br.
⁵ Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal do Maranhão, CCSST, Imperatriz, MA 65900-410, Brazil; Departamento de Física, Universidade Federal do Maranhão, CCET, São Luís, MA 65080-805, Brazil.

PMID: 35042044
DOI: 10.1016/j.saa.2022.120883

Abstract

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.

Keywords: DFT calculations; FTIR, and Raman spectroscopy; Phase changes; Thermal studies; Tris(glycinato) crystal; XRPD studies.