Síntese e caracterização: uma abordagem termogravimétrica, espectroscópica e estrutural de complexos de lantanídeos trivalentes Ce(III), Pr(III) E Nd(III) com o ligante 5-aminoisoftalato

Abstract

Compounds of lanthanide ions with organic ligand have attracted great interest from researchers in various fields of science and technology, as they may be indispensable for several applications such as magnetic resonance imaging, luminescent sensors, fiber optic lasers and amplifiers, electroluminescent materials and molecular materials magnetic, among others. In this sense, the objective of this work was to prepare 5-aminoisophthalate (AIF) compounds with lanthanide ions (Ce (III), Pr (III) and Nd (III)) and characterize them. The proposed study has followed a classical methodology for the synthesis of these compounds using the metals of the lanthanide series and with a ligand derived from the 5-aminoisophthalic acid (HAIF). A sodium salt solution (Na2AIF) was prepared and mixed by slowing dripping and stirring to the respective metal salt solutions (LnCl3) which were prepared from metal oxide by treatment with concentrated hydrochloric acid except for cerium, which had already been purchased as a salt (Ce(NO3)3). The impurities present in the precipitate were removed by washing with distilled water until negative test for the chloride and nitrate ions. The precipitate was oven dried at 60°C for 24 hours and then stored in a desiccator until analysis. The isolated solid state complexes were characterized by instrumental techniques such as thermogravimetric analysis and simultaneous differential scanning calorimetry (TG-DSC), by which it was possible to determine the number of hydration water molecules and the stoichiometric ratio (metal: binder) in the order of Ln2(IFA)3. nH2O, where n = 13 (Ce and Pr) and n = 12 (Nd). From spectroscopy data in the medium infrared region (FTIR/ATR), the coordination mode of the carboxylate groups of the ligand to the metal center was suggested as bidentate chelating coordination. From scanning electron microscopy (SEM) technique, it was possible to analyze the surface of the material in powder form. In addition, from x-ray data by powder method, it was possible to establish that the complexes obtained are isomorphic and polycrystalline.