Banca de DEFESA: LEONARDO DE OLIVEIRA AGUIAR

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LEONARDO DE OLIVEIRA AGUIAR
DATA : 14/06/2019
HORA: 09:00
LOCAL: Instituto de Química - Sala de Seminários
TÍTULO:

5,8-π-EXTENDED QUINOXALINE DERIVATIVES AS GOOD CHROMOFORMS FOR PHOTOLUMINESCENCE APPLICATIONS

PALAVRAS-CHAVES:

Quinoxaline, Liquid crystals, Luminescence

PÁGINAS: 100
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Orgânica
ESPECIALIDADE: Síntese Orgânica
RESUMO:

In this work, the synthesis, characterization and the study of thermal and photophysical properties of liquid-crystalline materials containing quinoxaline heterocycle are described, whose derivatives are known to present good performance in the construction of polymers, OLEDs and exhibit pronounced biological activity. To obtain new liquid crystals it is proposed the functionalization this heterocycle at positions 5 and 8, varying the coupled peripheral groups as a function of the alkyl chain length. The structural characteristics of the proposed molecules are capable of presenting calamitic mesomorphism and luminescent properties. The synthetic route to prepare the final compounds begins with the 4,7-dibromo-2,1,3-benzothiadiazole compound, involves reductive sulfur extrusion reaction, followed by cyclization using glyoxal. The final step of Sonogashira cross-coupling reaction allows obtaining the desired π-extended compounds. The synthesized molecules were characterized by spectroscopic techniques. The thermal properties were evaluated by DSC, TGA and MOLP, in addition to studies such as DRX. The final compounds exhibited nematic and smectic liquid-crystalline phases, typical for calamitic structures. The photophysical properties were studied by absorption and emission spectra in solution in chloroform, and it was possible to observe intense green luminescence when irradiated with UV-Vis light. The efficiency of the photoluminescence was evaluated by relative quantum yield in solution and the electrons lifetime study allows characterizing this process as fluorescence. In addition, solvatochromism was studied, applying the Lippert-Mataga equation, in order to evaluate the influence of the polarity of the solvent on the optical properties. Studies to determine the ability to act as a fluorescent sensor were performed through the interaction of quinoxaline derivatives with different metals. The photophysical properties of these materials were also investigated in solid phase by absorption and emission spectra and absolute quantum yield. The evaluation of the influence of heating in the optical properties was verified as well as the morphology of the thin films. Theoretical calculations, through DFT, allowed the comparison of the experimental data with the theoretical values.

MEMBROS DA BANCA:
Presidente - 2166886 - ANDRE ALEXANDRE VIEIRA
Interno - 1507716 - MAURICIO MORAES VICTOR
Interno - 1215450 - SILVIO DO DESTERRO CUNHA
Externo à Instituição - ALOIR ANTONIO MERLO - UFRGS