Investigation on the formation of highly luminescent β-diketone-Ln(III)-EDTA water-soluble complexes

Abstract

Three new β-diketone–Ln-EDTA (β-diketone=TTA, BTFA, ACAC; Ln=Eu3+ and Tb3+) water-soluble complexes were prepared, and their photophysical properties were investigated in aqueous solutions and compared with the Eu–EDTA complex. A very strong red and green luminescence was observed by the addition of ligands to the aqueous solutions of the Eu–EDTA and Tb–EDTA complexes, respectively, due to the formation of watersoluble β-diketone–Ln–EDTA complexes. To confirm the formation and stoichiometry of the new β- diketone–Ln–EDTA complex, the Judd–Ofelt intensity parameters Ω2 for Eu3+ complexes and the band width at half height (Δλ) for Tb3+ complexes were used. The dependence of these parameters on the addition of the β- diketone strongly suggests that only one β-diketonate ligand is in the first coordination sphere of the β- diketone–Ln–EDTA complexes. These new Eu3+ and Tb3+ systems may act as red and green optical markers for bioassay or bioimaging.