The Studies of Enhanced Fluorescence in the Two Novel Ternary Rare-Earth Complex Systems

Two novel ternary rare-earth complexes SmL₅·L^’·(ClO₄)₂·7H₂O and EuL₅·L^’·(ClO₄)₂·6H₂O (the first ligand L = C₆H₅COCH₂SOCH₂COC₆H₅, the second ligand L^’ = C₆H₄OHCOO⁻) were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC, ¹HNMR and UV spectra. The detailed luminescence studies on the rare-earth complexes showed that the ternary rare-earth complexes presented stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary rare-earth materials. After the introduction of the second ligand salicylic acid group, the relative emission intensities and fluorescence lifetimes of the ternary complexes LnL₅·L^’·(ClO₄)₂·nH₂O (Ln = Sm, Eu; n = 7, 6) enhanced more obviously than the binary complexes LnL₅·(ClO₄)₃·2H₂O. This indicated that the presence of both organic ligand bis(benzoylmethyl) sulfoxide and the second ligand salicylic acid could sensitize fluorescence intensities of rare-earth ions, and the introduction of salicylic acid group was a benefit for the fluorescence properties of the ternary rare-earth complexes. The fluorescence spectra, fluorescence lifetime and phosphorescence spectra were also discussed.