AvaliaÃÃo espectroscÃpica da substituiÃÃo sistemÃtica de molÃculas de Ãgua coordenadas por ligantes β-dicetonas em complexos com Ãons lantanÃdeos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In this work, lanthanide complexes with β-diketones (2,4-pentanedione and trifluoroacetylacetone) and β-keto esters (etil 4,4,4,-trifluoro-2,4- pentanedione) ligands have been synthesized. The complexes showed general formulas: [Ln(acac)(H2O)6]Cl2, [Ln(acac)2(H2O)4]Cl, [Ln(tfa)(H2O)6]Cl2, [Ln(tfa)2(H2O)4]Cl e [Ln(eta)2(H2O)4]Cl. The compounds were obtained in the powder form and were characterized by elemental analysis, IR and UV-vis spectroscopies, luminescence spectroscopy and lifetime measurements.The results are in agreement with the proposed formulas. Our objective was to investigate the luminescence intensification when the amount of β-diketones was varied. We also compared complexes of the one determinated β-diketone ligand with complexes of the one similar β-keto ester ligand. We determineted the non-radiative rates to the europium complexes through emission spectra data and lifetime measurements. The complex [Eu(acac)(H2O)6]Cl2 showed the larger non-radiative rate than the other complexs with the europium ion, and it correponds to 97% of the total rate. The complex [Eu(acac)2(H2O)4]Cl wich differs of the [Eu(acac)(H2O)6]Cl2 by one more ACAC ligand and by less two molecules of water, the non-radiative rate is around 75%, this difference can be attributed mainly to the number of water in each one of the complexs.

ASSUNTO(S)

espectroscopia complexes metals complexos metÃlicos lantanÃdeos quimica lanthanide spectroscopy

ACESSO AO ARTIGO

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