Complexos heterolépticos e heterobimetálicos de Eu(III) e Ir(III) utilizando ligantes ácidos carboxílicos e bases de Schiff
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Data
2019-02-28
Autores
Canisares, Felipe da Silva Manrique
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho a sensibilização do íon Eu(III) por complexos de Ir(III) foi testada através da formação de complexos heterobimetálicos Ir(III)-Eu(III) utilizando-se diferentes ligantes em ponte com coordenação ao irídio do tipo N^N e C^N e ao európio do tipo O^O e N^O. Assim, foi proposta uma metodologia adaptada para síntese de complexos heterolépticos de Ir(III) utilizando ligante com sitio coordenante do tipo N^N. A formação dos complexos de interesse foi comprovada com as seguintes fórmulas: [Ir(ppz)2(bpdc)] e [Ir(ppz)2(bqdc)], tornando o método de síntese viável, uma vez que reduz custo e tempo de síntese quando comparado aos métodos clássicos encontrados na literatura. Após a síntese dos complexos heterolépticos de Ir(III), foram sintetizados os complexos heterobimetálicos [(Cl)4Eu2(μ-bpdc)Ir(ppz)2] e [(Cl)4Eu2(μ-bqdc)Ir(ppz)2], com coordenação O^O ao Eu(III). No primeiro houve transferência parcial de energia ao íon Eu(III) e o segundo não apresentou emissão deste íon. Após a comparação dos espectros de emissão entre os complexos heterolépticos de Ir(III) e heterobimetálicos de Ir(III)-Eu(III) ficou claro que a coordenação de um segundo íon metálico com alto valor de acoplamento spin-orbital atua na diminuição do estado tripleto hibrido formado, dificultando o processo de transferência de energia. Os complexos monocentrados de Eu(III) com os ligantes bpdc e bqdc foram sintetizados e e tiveram suas estruturas determinadas. O complexo [Eu(bpdc)1,5(H2O)5]٠4H2O apresentou alta solubilidade em água e foi estabilizado em filme de látex, apresentando aumento de 371% da eficiência quântica de emissão. Também foram sintetizados e caracterizados dois ligantes bases de Schiff (N^O), S1 e S2, sendo S2 inédito na literatura. Estes ligantes foram sintetizados como estratégia para aumentar a energia do nível emissor nos complexos heterolépticos de Ir(III), uma vez que apresentam sítios ciclometalantes, C^N e ajudam a diminuir a distância entre orbitais 1MLCT e 3LC, que está diretamente relacionado com a energia do nível tripleto emissor; quanto menor a diferença, maior a energia do estado tripleto gerado. Os complexos heterolépticos de Ir(III) apresentaram luminescência na região do laranja/vermelho devido a uma provável coordenação pelo sítio C^N, fato este que tornou improvável a sensibilização do íon Eu(III), desta forma os complexos heterobimetálicos utilizando as bases de Schiff não foram sintetizados. Finalmente, um novo ligante ácido carboxílico, Fmpc (O^O) foi preparado, ácidos carboxílicos são conhecidos por apresentarem energias dos estados tripleto mais altos que bases de Schiff, desta forma possibilitam a formação de complexos emissores em comprimentos de onda menores. Desta forma foi obtido o complexo [Eu(μ-Fmpc)Ir(ppz)2] que ao comparar suas propriedades luminescentes ao complexo monocentrado de európio(III), o Na[Eu(Fmpc)4], mostrou aumento do tempo de vida do estado excitado 5D0, assim como maior eficiência quântica de emissão, demonstrando que complexos de metais de transição podem servir como sensibilizadores para o íon Eu(III).
In this work the sensitization of Eu(III) by Ir(III) complexes were tested through the formation of heterobimetallic Ir(III)-Eu(III) complexes with different bridge-ligands of the type N^N and C^N that coordinates to Ir(III), and O^O and N^O that coordinates to Eu(III). In this way, an adapted methodology for the synthesis of Ir(III) heteroleptic complexes using N^N ligands was proposed. The complexes formulae were confirmed as [Ir(ppz)2(bpdc)] and [Ir(ppz)2(bqdc)], what makes of this method a good alternative, since it reduces cost and time of synthesis when compared to classical methods reported in the literature. After the synthesis of the heteroleptic Ir(III) complexes, the heterobimetallic complexes [(Cl)4Eu2(μbpdc)Ir(ppz)2] and [(Cl)4Eu2(μ-bqdc)Ir(ppz)2] were synthesized, with the O^O coordination to the Eu(III). The first exhibited a partial energy transfer to Eu(III) while no emission from Eu(III) was observed for the second. It was clear afterwards that the coordination to a second metal ion with high spin-orbital coupling decreases the energy of the hybrid triplet state in the heterobimetallic complexes of Ir(III)-Eu(III), hindering the process of energy transfer. Eu(III) monocentralized complexes with bpdc and bqdc ligands were synthesized and characterized, which presented MOFs structures. The [Eu(bpdc)1,5(H2O)5]٠4H2O complex showed unusually high solubility in water and it was stabilized in latex film, increasing the quantum emission efficiency by 371%. Two Schiff bases ligands (N^O), S1 and S2, were also synthesized and characterized; S2 being unprecedented in the literature. These ligands were synthesized as a strategy to increase the energy of the emitter level in the Ir(III) heteroleptic complexes, since they have cyclometallating sites, C^N, resulting in a decrease of the energy distance between 1MLCT and 3LC orbitals, which is directly related with the energy of the triplet emitter level; the smaller the energy difference, the greater the energy of the triplet state. The Ir(III) heteroleptic complexes presented luminescence in the orange/red region probably due to the coordination through the C^N, waht made it unlikely to sensitize the Eu(III) ion, so the heterobimetallic complexes using the Schiff bases were not synthesized. Finally, a new carboxylic acid ligands, Fmpc (O^O) was shyntesized, carboxylic acids are known to have higher triplet states energies than Schiff's bases, thus enabling the formation of emitting complexes at lower wavelengths. So, the [Eu(μ-Fmpc)Ir(ppz)2] complex was obtained. By comparing the luminescent properties of the monocentered Eu(III) complex, Na[Eu(Fmpc)4], with the heterobimetallic one, the second showed an increase in the lifetime of 5D0, as well as a greater quantum emission efficiency.
In this work the sensitization of Eu(III) by Ir(III) complexes were tested through the formation of heterobimetallic Ir(III)-Eu(III) complexes with different bridge-ligands of the type N^N and C^N that coordinates to Ir(III), and O^O and N^O that coordinates to Eu(III). In this way, an adapted methodology for the synthesis of Ir(III) heteroleptic complexes using N^N ligands was proposed. The complexes formulae were confirmed as [Ir(ppz)2(bpdc)] and [Ir(ppz)2(bqdc)], what makes of this method a good alternative, since it reduces cost and time of synthesis when compared to classical methods reported in the literature. After the synthesis of the heteroleptic Ir(III) complexes, the heterobimetallic complexes [(Cl)4Eu2(μbpdc)Ir(ppz)2] and [(Cl)4Eu2(μ-bqdc)Ir(ppz)2] were synthesized, with the O^O coordination to the Eu(III). The first exhibited a partial energy transfer to Eu(III) while no emission from Eu(III) was observed for the second. It was clear afterwards that the coordination to a second metal ion with high spin-orbital coupling decreases the energy of the hybrid triplet state in the heterobimetallic complexes of Ir(III)-Eu(III), hindering the process of energy transfer. Eu(III) monocentralized complexes with bpdc and bqdc ligands were synthesized and characterized, which presented MOFs structures. The [Eu(bpdc)1,5(H2O)5]٠4H2O complex showed unusually high solubility in water and it was stabilized in latex film, increasing the quantum emission efficiency by 371%. Two Schiff bases ligands (N^O), S1 and S2, were also synthesized and characterized; S2 being unprecedented in the literature. These ligands were synthesized as a strategy to increase the energy of the emitter level in the Ir(III) heteroleptic complexes, since they have cyclometallating sites, C^N, resulting in a decrease of the energy distance between 1MLCT and 3LC orbitals, which is directly related with the energy of the triplet emitter level; the smaller the energy difference, the greater the energy of the triplet state. The Ir(III) heteroleptic complexes presented luminescence in the orange/red region probably due to the coordination through the C^N, waht made it unlikely to sensitize the Eu(III) ion, so the heterobimetallic complexes using the Schiff bases were not synthesized. Finally, a new carboxylic acid ligands, Fmpc (O^O) was shyntesized, carboxylic acids are known to have higher triplet states energies than Schiff's bases, thus enabling the formation of emitting complexes at lower wavelengths. So, the [Eu(μ-Fmpc)Ir(ppz)2] complex was obtained. By comparing the luminescent properties of the monocentered Eu(III) complex, Na[Eu(Fmpc)4], with the heterobimetallic one, the second showed an increase in the lifetime of 5D0, as well as a greater quantum emission efficiency.
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Terras raras, Efeito antena, Európio, Complexos, OLEDs, Rare earths, Antenna effect, Europium, Complex