Molecular γ-amino butyric acid and its crystals: Structural, electronic and optical properties

This work presents the formation of monoclinic γ-aminobutyric acid (GABA) crystals grown from an aqueous ethanol solution with the dimensions 4 ​× ​1 ​× ​0.6 ​mm3. The structural properties of the grown crystal were evaluated via X-ray diffraction analysis of the powder and single crystal, which confirmed a monoclinic crystal system with space group P21/c. Thermal stability and the melting point of the synthesized GABA crystal were investigated using TG-DSC measurements. We also characterized experimentally monoclinic and molecular GABA solvated in water, obtaining its optical absorption spectrum in the UV-VIS region. Time-dependent DFT calculations were performed for the GABA molecule in the neutral and zwitterion forms to understand their optical absorption features. Structural, electronic, and optical properties of four γ-aminobutyric acid (GABA) crystal polymorphs (monoclinic, tetragonal, hexagonal, and monohydrate) were achieved through DFT calculations employing a dispersion corrected exchange-correlation functional. Differences in the electronic and optical properties between polymorphs are discussed. We predict the GABA monoclinic crystal to be an indirect gap semiconductor with a gap value of 5.02 ​eV, in good agreement with our experimental measurements. Considering the other three polymorphs, their fundamental gap values range from 4.6 ​eV to 5.16 ​eV (being direct for all of them, except the monohydrate). The absorption spectra calculations reveal a significant optical anisotropy for all GABA crystals, with the highest optical absorption for the monoclinic structure in the 5–6 ​eV energy range.

• Autores: Silva, José Barbosa; Torrente Rocha, Juan Jose; Niño Rodriguez, claudia patricia; de Paula, Valdir Ferreira; Guedes, Maria Izabel Florindo; e Silva, Bruno Poti; Valentini, Antoninho; Gonzalez Santos, Jeni Bianda; Freire, Valder Nogueira
• Tipo de recurso: Article of investigation
• Fecha de publicación: 2023
• Institución: Universidad de Ibagué
• Repositorio: Repositorio Universidad de Ibagué
• Idioma: eng
• OAI Identifier: oai:repositorio.unibague.edu.co:20.500.12313/5539
• Acceso en línea: https://hdl.handle.net/20.500.12313/5539; https://www.sciencedirect.com/science/article/pii/S0022459623000683
• Palabra clave: Ácido γ-aminobutírico molecular y sus cristales - Propiedades estructurales; Ácido γ-aminobutírico molecular y sus cristales - Propiedades electrónica; DFT calculations; GABA polymorphs Crystals; Optical properties; Structural properties; γ-amino butyric acid (GABA) crystal
• Rights: closedAccess
• License: © 2023 Elsevier Inc.