Síntese e investigação da potencialidade de aplicação como material molecular de espécies discretas e Metal Organic Frameworks (MOFs) baseados em íons terras raras
Carregando...
Arquivos
Data
2016-08-11
Autores
Lahoud, Marcelo Galindo [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho é dividido em duas partes, na primeira parte foi caracterizado o complexo [Ln(keto)3(H2O)] (Ln = Gd, Eu) por espectroscopia vibracional no infravermelho, analise elementar e otimização da geometria por método DFT. Mas o foco central foram os estudos das propriedades luminescente no intervalo de 12 – 300 K. O espectro de emissão do [Eu(keto)3(H2O)] revela uma forte dependência com a temperatura, bem ilustrada pelo não usual deslocamento amplo para o azul de (17 cm1) da transição 5D07F0 quando a temperatura é elevada de 12 a 300 K. A diferença aritmética entre os espectros de absorção do [Eu(keto)3(H2O)] com o do [Gd(keto)3(H2O)] indicou a presença de uma banda de transferência de carga do ligante para o metal (LMCT) (320-370 nm). A partir da fosforescência do [Gd(keto)3(H2O)] a energia dos estados de tripleto relacionada ao Keto foi determinada mostrando uma grande sobreposição com os níveis intra-4f6 e um forte acoplamento elétron-fônon. A alta ressonância entre o nível LMCT e estados tripletos e os níveis do Eu3+ leva a uma forte dependência do valor do tempo de vida da 5D0, típico da presença de processos de transferência de energia operativos. A segunda parte desse trabalho compreendeu na síntese, caracterização e estudos das propriedades luminescente e magnéticas de uma MOF inédito de formula [Eu2(Btec)1,5(H2O)]n. A MOF foi sintetizada por via hidrotermal e caracterizado por DRX de monocristal e pó, espectroscopia vibracional no infravermelho, reflectância difusa, analise elementar, analise térmica, microscopia eletrônica de varredura e fisissorção de N2. O composto apresentou boa estabilidade térmica no entanto mostrou-se ter baixa porosidade. A MOF apresentou emissão na região do vermelho com elevado rendimento quântico de emissão, mostrando que o ligante é um bom sensibilizador nesse sistema. As emissões dos íons Eu3+ mostraram-se ser uma sonda espectroscópica, contribuindo na elucidação da estrutura. Foi observado uma dependência térmica em relação à intensidade das transições originárias do nível 7F1, em especial a transição 7F15D1. Além disso, as transições intraconfiguracionais 4f-4f mostram ter uma boa fotoestabilidade. Resultados de susceptibilidade magnética mostram íons Eu3+ magneticamente afastados e portanto os torna uma fraca probe estrutural.
This work is divided into two parts, the first part was characterized the complex [Ln(keto)3(H2O)] (Ln = Gd, Eu) by infrared spectroscopy, elemental analysis and geometry optimization by DFT method. But the central focus was the study of luminescent properties in the 12-300 K interval. The emission spectra of [Eu(keto)3(H2O)] reveal a strong dependence with the temperature, well-illustrated by an unusual large blue-shift (17 cm1) of the 5D07F0 transition as the temperature is raised from 12 to 300 K. The arithmetic difference between the absorption spectrum of [Eu(keto)3(H2O)] with that of [Gd(keto)3(H2O)] pointed out the presence of a ligand-to-metal charge transfer (LMCT) band (320-370 nm). From the [Gd(keto)3(H2O)] phosphorescence the energy of the keto-related triplet states was determined showing a large overlap with the intra-4f 6 levels and a strong electron-phonon coupling. The high-resonance between the LMCT and triplet states and the Eu3+ levels leads to a strong dependence of the 5D0 lifetime value, typical of the presence of operative energy transfer processes. The second part of this work included in the synthesis, characterization and study of luminescence and magnetic properties of a novel MOF formula [Eu2(Btec)1,5(H2O)]n. The MOF was synthesized by way hydrothermal and characterized by XRD of single crystal and powder, infrared spectroscopy, diffuse reflectance, elemental analysis, thermal analysis, scanning electron microscopy and N2 physisorption. Compound demonstrated good thermal stability however proved to have low porosity. MOF showed emission in the red region with a high emission quantum yield, showing that the ligand is a good sensitizer in the system. The emission of Eu3+ ions proved to be a spectroscopic probe, contributing to the elucidation of the structure. A thermal dependence was observed in relation to the intensity of originating 7F1 level transitions, in particular the 7F15D1 transition. Furthermore, the 4f-4f transitions intraconfigurational shown to have a good photostability. Magnetic susceptibility results show Eu3+ ions separated magnetically and thus makes a weak probe structure.
This work is divided into two parts, the first part was characterized the complex [Ln(keto)3(H2O)] (Ln = Gd, Eu) by infrared spectroscopy, elemental analysis and geometry optimization by DFT method. But the central focus was the study of luminescent properties in the 12-300 K interval. The emission spectra of [Eu(keto)3(H2O)] reveal a strong dependence with the temperature, well-illustrated by an unusual large blue-shift (17 cm1) of the 5D07F0 transition as the temperature is raised from 12 to 300 K. The arithmetic difference between the absorption spectrum of [Eu(keto)3(H2O)] with that of [Gd(keto)3(H2O)] pointed out the presence of a ligand-to-metal charge transfer (LMCT) band (320-370 nm). From the [Gd(keto)3(H2O)] phosphorescence the energy of the keto-related triplet states was determined showing a large overlap with the intra-4f 6 levels and a strong electron-phonon coupling. The high-resonance between the LMCT and triplet states and the Eu3+ levels leads to a strong dependence of the 5D0 lifetime value, typical of the presence of operative energy transfer processes. The second part of this work included in the synthesis, characterization and study of luminescence and magnetic properties of a novel MOF formula [Eu2(Btec)1,5(H2O)]n. The MOF was synthesized by way hydrothermal and characterized by XRD of single crystal and powder, infrared spectroscopy, diffuse reflectance, elemental analysis, thermal analysis, scanning electron microscopy and N2 physisorption. Compound demonstrated good thermal stability however proved to have low porosity. MOF showed emission in the red region with a high emission quantum yield, showing that the ligand is a good sensitizer in the system. The emission of Eu3+ ions proved to be a spectroscopic probe, contributing to the elucidation of the structure. A thermal dependence was observed in relation to the intensity of originating 7F1 level transitions, in particular the 7F15D1 transition. Furthermore, the 4f-4f transitions intraconfigurational shown to have a good photostability. Magnetic susceptibility results show Eu3+ ions separated magnetically and thus makes a weak probe structure.
Descrição
Palavras-chave
Európio, MOFs, Complexo luminescente, Luminescent complex, Europium