Raman spectroscopy of captopril crystals under low-temperature conditions.

D L M Vasconcelos, F F de Sousa, J G da Silva Filho, A M R Teixeira, P F Façanha Filho, P R S Ribeiro, P T C Freire

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy 2020 Dec 15

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The polymorphism is a characteristic of several active principles, and can affect the bioavailability of a drug. Among the drugs used in the treatment of heart diseases, captopril is one of the most widely used in the world. Despite the knowledge of vibrational properties of captopril under high temperature and under high pressure, a lack of information impedes the understanding of the substance in the crystal form at low temperatures. In this research, we investigated the vibrational properties of captopril crystals under cryogenic conditions in the 300-8 K interval using Raman spectroscopy. By observing the behavior of the inter- and intra-molecular vibrations it was possible to infer that the captopril molecules suffered a rearranging into the unit cell due slight orientational changes mainly involving CH⋯O hydrogen bonds. The phenomenon occurs in a large temperature range. However, the observed changes do not suggest the occurrence of a structural phase transition and the Raman spectra indicate that the trans conformation is recorded down to the lowest temperature available in the experiments. Copyright © 2020 Elsevier B.V. All rights reserved.

Citation

D L M Vasconcelos, F F de Sousa, J G da Silva Filho, A M R Teixeira, P F Façanha Filho, P R S Ribeiro, P T C Freire. Raman spectroscopy of captopril crystals under low-temperature conditions. Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 2020 Dec 15;243:118734