Banca de QUALIFICAÇÃO: GENICKSON BORGES DE CARVALHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : GENICKSON BORGES DE CARVALHO
DATA : 17/06/2016
HORA: 14:00
LOCAL: Sala 3F1
TÍTULO:

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

PALAVRAS-CHAVES:

Complexes. Luminescence. Pyrazinecarboxamide. Lanthanides

PÁGINAS: 248
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Foto-Química Inorgânica
RESUMO:

This work describes the synthesis and characterization of coordination compounds between lanthanide nitrate (III) and pyrazinecarboxamide (PyZ) aiming at a possible functional application of these new compounds as molecular light conversion devices. The obtained compounds were characterized by various analytical techniques which we can highlight: Elemental analysis, thermogravimetry (TG) and simultaneous Differential Thermal Analysis (DTA), Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FT-IR), Diffraction X-ray (XRD) by the powder method Conductivity Electrolyte Molar, absorption spectroscopy in UV-visible, and also the absorption spectroscopy in the visible to neodymium compound at 298 K and luminescence spectroscopy at 298 K. The results of elemental analysis allowed proposing the following molecular formula: [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 provided information about the dehydration and thermal decomposition of these complexes. The molar conductivity data both in nitromethane as suggested in acetonitrile electrolyte behavior of 1:1 for all compounds, reinforcing IR results that indicated the presence of nitrate not coordinated to the lanthanide ion. In the electronic spectra of UV-Vis observed displacement of the absorption bands of the studied complexes when compared to the bands of the binder, suggesting the coordination of the lanthanide ion with the binder pyrazinecarboxamide. Absorption spectra in the infrared region allowed to establish that the coordination site of PyZ binder with the metal ion is the carbonyl oxygen and the alpha nitrogen pyrazine ring. The 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 298K allowed determining the spectroscopic parameters whose numerical values indicate that metal-ligand interaction is essentially electrostatic. From the electronic spectra in acetonitrile and ethanol solution, the oscillator strength (P) was calculated and its values suggest that the disturbance of coordination sphere of the ion Nd³⁺ be higher when there is solubilization in ethanol. The analysis of the europium emission spectrum of compound solid at 298K leads to suggest a microsymmetry close to D_2d with consistent distortion with the geometry of a dodecahedron. Luminescence analysis indicates that the complexes Eu³⁺, Tb³⁺, Sm³⁺ and Dy³⁺ have emission characteristics in the region of lanthanide ions; however, when in acetonitrile solution, just the compound of samarium showed no emission in the visible region due to having possibly its luminance suppressed by the presence of this solvent.

MEMBROS DA BANCA:
Presidente - 7350310 - MARIA DE FATIMA VITORIA DE MOURA
Interno - 350633 - ADEMIR OLIVEIRA DA SILVA
Interno - 345799 - OTOM ANSELMO DE OLIVEIRA
Externo ao Programa - 338292 - JOÃO BOSCO LUCENA DE OLIVEIRA