Estudo espectroscópico de sistemas contendo o íon európio trivalente

• Autor(a) principal: Jesus, Larissa Tavares de
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/7940
• topic: Química; Európio; Ibuprofeno; Compostos nitrogenados; Luminescência; Eu3+; Ligantes β-dicetonados fluorados; Ligantes Nitrogenados; Fluorinated β-diketonate ligands; Nitrogen ligands; Luminescence; CIENCIAS EXATAS E DA TERRA::QUIMICA

In this work a theoretical study was carried out to investigate the spectroscopic properties of trivalent europium complexes. The study was divided into two parts. The first one was the study of the luminescent efficiency of five complexes which had as ligands β-diketones and pyrazole. Pyrazole modifications were made promoting a gradual increase in the amount of fluorine atoms in the search for systems with greater luminescence. The second part was the study of structural elucidation and luminescent efficiency of two Eu3+ complexes, which showed as ligand the molecule of ibuprofen and methylbipyridine. The difference between the two systems was that in one complex the methyl group of bipyridine was in the meta position and in the other in the para position. Semiempirical methodologies such as the Sparkle models, the INDO/S-CIS method, the Judd-Ofelt theory and the energy transfer models proposed by Malta et al were used to certify this. The theories and models used to treat the spectroscopic properties of these systems are implemented in the LUMPAC - Luminescence Package, which was used in this study. In the first part, an evaluation of calculation models of the ground state geometry more suitable for the study and from comparisons with crystallographic structures the model that presented smaller error was the Sparkle/PM3. From the results obtained, it has been seen that the luminescence intensity of the Eu3+ complexes increases when the C-H bonds are replaced by C-F bonds, and more strongly when CF2 groups are added. Further extension in the length of the fluorinated chain greatly decreases the rate of nonradiative decay and increases the rate of radiative decay, thereby increasing the quantum efficiency of the complex. The results obtained were theoretically compared with the experimental results and showed good agreement. In the second part of the work, no evaluation of the geometry calculation model was performed, since it is a system that does not have certain crystallographic structures. Thus, the RM1 model was used to optimize the geometry, since it is a recent model that satisfactorily treats lanthanide systems. The results obtained did not show much difference, that is, the position of the methyl group in the meta or para position in the bipyridine linker does not cause considerable effect on the coordination polyhedron. However, they presented higher radiative decay rates than the rates of non-radiative decay and high quantum efficiency. Finally, the good agreement between the theoretical results and the experimental results is a strong indicatio