Uma investigaÃÃo teÃrica e experimental das propriedades luminescentes de novos complexos de lantanÃdeos com β-cetoÃsteres

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The theoretical and experimental study of the luminescent properties of the complexes of trivalent europium, terbium and gadolinium ions with β-ketoesthers, ethyl 4,4,4-trifluoroacetoacetate (ETA), ethyl acetoacetate (EAA), methyl 4-methoxy acetoacetate (MMA) and ethyl benzoilacetoacetate (EBA) ligands revealed a new class of complexes that present optical properties similar to complexes with ligands β- diketones. These compounds are, therefore, potentially useful as light converting molecular devices. The complexes show the characteristic transistions of the ions lanthanide, except for the case with ligante EBA, where the typical emission from the terbium ion in the green region was not observed. The emission spectra of the gadolinium show that the ligands triplet states are resonant with the excited states of the europium and terbium ions, leading to efficient ligand-to-metal intramolecular energy transfer. The optimized coordination geometries obtained from the SMCL model (Sparkle Model for the Calculations of Lanthanide Complexes) pointed to a chemical enviroment of very low symmetry around the lanthanide ion (C1), in agreement with the luminescence spectra, particularly in the case of the europiumion in which the 5D0→7F0 transition is present. The theoretical 4f-4f intensities parameters are in good agreement with the experimental values. The calculations have shown that the dynamic coupling mechanism ) ( . .D Aλ Ω is dominant

ASSUNTO(S)

modelo smcl quimica -cetoÃster complexos de lantanÃdeos β -ketoesthers smcl model complexes of lanthanide β

ACESSO AO ARTIGO

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