Síntese, caracterização e atividade antimicrobiana do complexo catena-[(μ-glicinato)-nitrato de prata]

Abstract

Coordination complexes are formed by a central ion, a metal, bonded to one or more ligands. These materials have garnered significant scientific attention over years, primarily due to their biological properties, especially antibacterial and antitumor activities. In this study, a crystalline complex, Catena-[(μ-glycinato)-silver nitrate], was synthesized and its physicochemical properties were characterized, alongside an evaluation of its potential biological activity. The crystal was obtained using the slow solvent evaporation technique.

After its synthesis, the crystal was characterized using X-ray diffraction (XRD), ultraviolet- visible (UV-Vis) absorbance spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy,

Raman spectroscopy, thermogravimetric analysis (TG), differential thermal analysis (DTA) and temperature-variable XRD (27 to 143 °C). Furthermore, a computational study using density functional theory (DFT) was conducted. Additionally, the antimicrobial activity of the material was assessed. With the assistance of X-ray diffraction (XRD) at room temperature (25 °C), it was observed that the obtained material grew in monoclinic system, with P21/a (C2h 5 ) space group, containing four formulas per unit cell (Z = 4). The refined Rietveld lattice parameters were: a = 5,442(9) Å, b = 19,431(5) Å, c = 5,534(4) Å, with V= 576,606 Å3 and β = 99,943°. UV-Vis spectroscopy analysis indicated no d-d transition (no visible band) for the d 10 electronic configuration. The computational study provided the optimized molecular geometry, electrostatic potential map, spatial distribution, and energy of HOMO and LUMO orbitals, as well as descriptors of chemical reactivity. Experimental IR and Raman spectra were obtained and compared to theoretical spectra calculated through DFT calculations. Thermoanalytical techniques were employed to assess the material's thermal stability, revealing that it remains stable above 100 °C. Nevertheless, an observed potential phase transition at around 117 °C prompted further investigation. Subsequent X-ray diffraction (DRX) results, conducted at various temperatures, unequivocally confirmed the material's phase transition. Utilizing the Le Bail method, it was determined that the material transitioned to the triclinic system with space group P1 (C1 1 ), with the following lattice parameters: a =

12,1852 Å, b = 8,8919 Å, c = 14,6299 Å, with V = 1453,074 Å3

and β = 98,948°. Antibacterial analysis demonstrated that the material exhibits significant activity (MIC = 62.5 μg/mL) against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Therefore, the obtained data suggest that the crystalline complex has properties favorable for biological applications.