Síntese, caracterização e estudo do comportamento térmico dos picolinatos de lantanídeos no estado sólido
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2018-12-17
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Universidade Estadual Paulista (Unesp)
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O presente trabalho de pesquisa visou a síntese, caracterização e estudo termoanalítico dos picolinatos de lantanídeos (III) e de ítrio (III), exceto o promécio, no estado sólido. Esses compostos foram investigados utilizando-se método complexométrico, difração de raios X, análise elementar, espectroscopia de reflectância total atenuada na região do infravermelho, termogravimetria e calorimetria exploratória diferencial simultâneas (TG-DSC), microscopia hot-stage (HSM), calorimetria exploratória diferencial (DSC) e técnicas de análise dos gases liberados (EGA) como a termogravimetria e calorimetria exploratória diferencial simultâneas acoplada à espectroscopia de absorção na região do infravermelho com transformada de Fourier (TG-DSC/FTIR) e a microscopia hot-stage acoplada a espectrômetro de massas (HSM-MS). Cálculos teóricos foram realizados para a elaboração de modelos estruturais mais prováveis e energeticamente favoráveis dos compostos sintetizados. Para o estudo de propriedades eletrônicas dos complexos foram aplicados métodos da Teoria Densidade Funcional Eletrônica (DFT) e para esses cálculos o programa Gaussian 2003 foi empregado. Os resultados obtidos permitiram o estabelecimento de estequiometria, verificar a estabilidade, o comportamento térmico e identificação dos produtos gasosos liberados durante o aquecimento desses compostos. A síntese foi realizada por vias diferentes nos compostos da série dos leves (Lantânio ao Gadolínio) e da série dos pesados (Térbio ao Lutécio e ítrio) utilizando-se ureia como reagente da síntese em meio homogêneo. Todos os picolinato de lantanídeos trivalentes leves são cristalinos e foram obtidos em estado anidro, por outro lado, os picolinato de lantanídeos trivalentes pesados e ítrio, possuem grau de hidratação que variou entre 1,5 à 2,5 H2O, estão no estado amorfo e muitos são inéditos na literatura.
The present study aimed the synthesis, characterization and thermoanalytical study of lanthanide (III) and yttrium (III) picolinates, except promethium, in the solid state. These compounds were investigated using complexometric method, X-ray diffraction, elemental analysis, attenuated total reflectance spectroscopy in the infrared region, simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), hot-stage microscopy (HSM), differential scanning calorimetry (DSC) and evolved gas analysis (EGA) techniques as simultaneous thermogravimetry and differential scanning calorimetry coupled to absorption spectroscopy in the infrared region with Fourier transform (TG-DSC / FTIR) and hot-stage microscopy coupled to a quadrupole mass spectrometer (HSM-MS). Theoretical calculations were carried out for the elaboration of more probable and energetically favorable structural models of the synthesized compounds. For the study of electronic properties of the complexes were applied methods of Electronic Functional Density Theory (DFT). For these calculations, the Gaussian 2003 program was used. The results obtained allowed the establishment of stoichiometry, to verify the stability, thermal behavior and identification of the gaseous products released during the heating of these compounds. The synthesis was performed by different routes in the compounds of the light series (Lanthanium to Gadolinium) and the heavy series (Terbium to Lutetium and Yttrium) using urea as a reagent of the synthesis in homogeneous medium. All light trivalent lanthanide picolinates are crystalline and have been obtained in the anhydrous state; on the other hand, heavy trivalent lanthanide picolinates and yttrium, have a hydration degree ranging from 1.5 to 2.5 H2O, are amorphous and many are unpublished in the literature.
The present study aimed the synthesis, characterization and thermoanalytical study of lanthanide (III) and yttrium (III) picolinates, except promethium, in the solid state. These compounds were investigated using complexometric method, X-ray diffraction, elemental analysis, attenuated total reflectance spectroscopy in the infrared region, simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), hot-stage microscopy (HSM), differential scanning calorimetry (DSC) and evolved gas analysis (EGA) techniques as simultaneous thermogravimetry and differential scanning calorimetry coupled to absorption spectroscopy in the infrared region with Fourier transform (TG-DSC / FTIR) and hot-stage microscopy coupled to a quadrupole mass spectrometer (HSM-MS). Theoretical calculations were carried out for the elaboration of more probable and energetically favorable structural models of the synthesized compounds. For the study of electronic properties of the complexes were applied methods of Electronic Functional Density Theory (DFT). For these calculations, the Gaussian 2003 program was used. The results obtained allowed the establishment of stoichiometry, to verify the stability, thermal behavior and identification of the gaseous products released during the heating of these compounds. The synthesis was performed by different routes in the compounds of the light series (Lanthanium to Gadolinium) and the heavy series (Terbium to Lutetium and Yttrium) using urea as a reagent of the synthesis in homogeneous medium. All light trivalent lanthanide picolinates are crystalline and have been obtained in the anhydrous state; on the other hand, heavy trivalent lanthanide picolinates and yttrium, have a hydration degree ranging from 1.5 to 2.5 H2O, are amorphous and many are unpublished in the literature.
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Ácidos carboxílicos, Terras raras, Complexos metálicos, Uréia, Análise Térmica