Síntese e caracterização do cristal Dicloro (L-histidina) cobre(II)

Abstract

Metal complexes have been widely studied due to their diverse applications, both in the technological and biological fields. Among these complexes are those formed by copper (II) and L-histidine. In this context, this work aimed to synthesize the Dichloro (L-histidine) copper (II) crystal by the slow evaporation solvent method. The crystal was obtained in a 1:1 ratio and characterized by ultraviolet-visible spectroscopy (UV-vis), computational calculations by density functional theory (DFT), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), and the antimicrobial activity. Through UV-vis it was possible to observe that the crystal presents a band with maximum absorption at a wavelength of 600 nm, attributed to the common d-d transitions in copper (II) complexes. The XRD with Rietveld method refinement confirmed that the synthesized crystal crystallizes with 4 molecules per unit cell, orthorhombic structure and P212121(D2 4 ) space group, with lattice parameters a= 9.992 (7) Å, b= 5.937 (9) Å, c= 17.472 (6) Å e V= 1036.3 (6) Å3. The optimized crystal structure was calculated using DFT, making it possible to obtain the chemical reactivity of the complex from the HOMO and LUMO border orbitals, the molecular electrostatic potential (MEP), as well as the chemical reactivity indices, which showed that the crystal is stable. According to the results of the TG-DTA techniques, the complex presented two thermal events, the first was attributed to fusion followed by decomposition, and the second event was related to the oxidation of the material. It was verified by the DSC curve that the crystal melting occurs at approximately 475 K. With the theoretical and experimental FT-IR and Raman spectra, it was possible to carry out the attributions and comparisons of the vibrational modes of the crystal. Through the results of XRD as a function of temperature, in agreement with the analytical thermal techniques, it was verified that the crystal has thermal structural stability up to approximately 463 K. Based on the studies of the evaluation of the antimicrobial activity, it was observed that the crystal Dichloro (L-histidine) copper (II) showed good biocidal activity against Gram (+) Staphylococcus aureus bacteria strain.