Banca de DEFESA: GENICKSON BORGES DE CARVALHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : GENICKSON BORGES DE CARVALHO
DATA : 29/07/2016
HORA: 14:00
LOCAL: Sala 3F1
TÍTULO:

SYNTHESIS, CHARACTERIZATION AND INVESTIGATION OF THE PHOTOLUMINESCENCE PYRAZINECARBOXAMIDE COMPLEXES WITH LANTHANIDES ÍONS

PALAVRAS-CHAVES:

Complexes. Luminescence. Pyrazinecarboxamide. Lanthanides

PÁGINAS: 233
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Campos de Coordenação
RESUMO:

The present work describes the synthesis and characterization of coordination compounds between lanthanide nitrate (III) and pyrazinecarboxamide (PyZ), to a possible functional application of these new compounds as molecular light conversion devices. The obtained compounds were characterized by various analytical techniques, of which we highlight: Elemental Analysis, Thermogravimetry (TG) and Differential Thermal Analysis (DTA) simultaneous, Differential Scanning Calorimetry (DSC), Absorption Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) powder by method Electrolytic Conductivity Molar Absorption Spectroscopy Electronics (UV-Vis) at 298 K and luminescence spectroscopy at 298 K. From the results of elemental analysis, thermogravimetry Conductivity and Molar it was possible to propose the following molecular formulas: [Ln(PyZ)₂(NO₃)₂]NO₃.2H₂O (Ln³⁺ = La-Eu) and [Ln(PyZ)₂(NO₃)₂]NO₃.H₂O (Ln³⁺ = Gd-Dy). The TG-DTA and DSC curves provide information regarding the dehydration, decomposition, and thermal stability of the synthesized compounds. The molar conductivity data both in nitromethane as in acetonitrile suggested electrolyte behavior of 1:1 for all compounds, reinforcing the results of the absorption spectra in the infrared region, which indicated the presence of nitrate is not coordinated to the lanthanide ion. In the electronic spectra UV-Vis, displacement of the absorption bands of the studied complexes was observed when compared to the free ligand bands, suggesting the coordination of the lanthanide ion with the binder pyrazinecarboxamide. The absorption spectra in the infrared allowed to establish that the coordination sites of the PyZ binder with the metal ion are carbonyl oxygen and nitrogen alpha pyrazine ring. Interpretation of the diffractograms X-ray obtained by the powder method allowed the establishment of three isomorphic series: the first comprises those compounds of La³⁺ and Ce³⁺, the second compounds of Pr³⁺ at Tb³⁺ and the third to the Dy³⁺ compound. The study of hypersensitive bands of the neodymium compound in solid state at 298 K allowed the determination of spectroscopic parameters, numerical values which indicate that metal-ligand interaction is essentially electrostatic. The oscillator strength (P) was calculated from the electronic spectra in acetonitrile and ethanol solution, and its values suggest that the disturbance of the Nd³⁺ ion coordination sphere to be higher when solubilized in ethanol. The emission spectrum of the gadolinium complex showed that the energy of the excited triplet state of the ligand PyZ is above the emitting level of the ions Eu and Tb, which favors the process of metal-ligand energy transfer. The analysis of the europium compound emission spectrum in the solid state at 298 K suggested a microssimetria next to D_2d distortion with consistent with the geometry of a dodecahedron. Luminescence analysis indicated that the complex of Eu³⁺, Tb³⁺, Sm³⁺ and Dy³⁺ have characteristics emissions in the region of lanthanide ions, whereas in the acetonitrile solution, only the compound of samarium showed no emission in the visible region by possibly having its luminescence suppressed by the presence of this solvent.

MEMBROS DA BANCA:
Interno - 350633 - ADEMIR OLIVEIRA DA SILVA
Externo à Instituição - CLEIDE MARIA DA SILVA LEITE - UNILAB
Externo à Instituição - DANIEL FREITAS FREIRE MARTINS - UFERSA
Externo ao Programa - 3432383 - FILIPE MARTEL DE MAGALHAES BORGES
Externo ao Programa - 008.363.534-39 - KLECIA MORAIS DOS SANTOS - CAPES
Presidente - 7350310 - MARIA DE FATIMA VITORIA DE MOURA
Interno - 345799 - OTOM ANSELMO DE OLIVEIRA