Synthesis And Luminescent Properties Of The Functional Complexes Of Aromatic Carboxylic Acids With α-thenoyltrifluoroacetone Europium(Ⅲ)

In recent years, much attention has been paid to the design, syntheses and properties of the complexes of rare earth ions. An important aspect of this research field is to optimize the luminescent properties of the rare earth ion and the thermal-optical stability of the complex by a suitable selection of ligands. Europiun(â…¢) complexes with P-diketones ligands have the high luminescene efficiencies and good compatibility with resin; however, they are very limited for practical application in light conversion agents due to their poor thermal-optical stability and low mechanical resistances. The luminescent efficiencies of europium(â…¢) carboxylates are low; but they have good thermal-optical stability. In this research, valuable explorations about the design and syntheses of efficient light conversion agents, which have good thermal-optical stability, were carried out. Some new europium(â…¢) complexes were synthesized. These complexes were characterized by elemental analysis, IR spectroscopy, scanning electronic microscopy, thermal analysis and fluorescent spectra et al. The relationship between the structure and the luminescent properties together with thermal-optical stability of the complexes were discussed. Some valuable results were obtained. The main works are as follows:Six europium(â…¢) complexes ofα-thenoyltrifluoroacetone (HTTA) with benzoic acid (BA) or its two derivatives, p-toluic acid (PTA) and p-methoxybenzoic acid (POA), and phenanthroline (Phen) or trioctylpho-sphine oxide (TPPO) were synthesized. Compositions of these complexes are revealed to be Eu(BA)(TTA)₂Phen, Eu(PTA)(TTA)₂Phen, Eu(POA) (TTA)₂Phen, Eu(BA)(TTA)₂TPPO₂, Eu(PTA)(TTA)₂TPPO₂ and Eu(POA) (TTA)₂TPPO₂. The analytical results of IR spectroscopy, thermal stability and cofluorescence show that the complexes of the above mentioned have the similar mononuclear chemical structure. The excitation and absorption spectra of the complexes Eu(POA)(TTA)₂Phen and Eu(POA)(TTA)₂TPPO₂ in MeOH solution were investigated in detail. The luminescent lifetime values and quantum efficiencies of the complexes Eu(POA)(TTA)₂Phen and Eu(POA)(TTA)₂TPPO₂ were measured. And the radiative (A_rad), non-radiative (A_nrad), and the energy transfer efficiencies from the excited state of the ligand to the emitting state of the europium(â…¢) ions were calculated. Cofluorescence of Gd³⁺ in these mononuclear Eu(â…¢) complexes was investigated in solids and in MeOH solution. The result showes that the complexes of the above mentioned have the long luminescent lifetimes and high quantum efficiencies, and cofluorescence is found in solids but not in MeOH solution.The bridging ligand, terephthalic acid (TPA), is reported firstly to be used to link europiun(â…¢) ions to form four new europium(â…¢) complexes Eu₂(TPA)(TTA)₄Phen2, Eu₂(TPA)(TTA)₄(TPPO)₄, Eu(TPA)(TTA)Phen and Eu(TPA)(TTA)(TPPO)₂. Their chemical structures proposed are the binuclear for Eu₂(TPA)(TTA)₄Phen₂, Eu₂(TPA) (TTA)₄TPPO₂ and the chain polynuclear for Eu(TPA)(TTA)Phen, Eu(TPA)(TTA)TPPO₂. The excitation and emission spectra together with luminescent lifetimes of these complexes had been systematically measured, at room and liquid nitrogen temperature. The radiative (A_rad), non-radiative (A_nrad), the quantum efficiencies (η) of the emitting ⁵D₀ level and the values of the experimental intensity parameters (Ω_J) of the above mentioned complexes were calculated. The results show that the above mentioned complexes have long luminescent lifetimes and good thermal-optical stability, and the Eu(â…¢) ion in four new complexes is in a less polarizable chemical environment.Cofluorescence of Gd(â…¢) / Y(â…¢) for the binuclear complexes Eu_2(1-x) Gd_2x(TPA)(TTA)₄Phen₂ and Eu_2(1-x)Y_2x(TPA)(TTA)₄(TPPO)₄ was investigated in solids for the first time. Both intermolecular energy transfer and intra molecular energy transfer in cross binuclear molecules are thought to be responsible for the cofluorescence of the binuclear complex powders. The combinatorial molecular library of the effect of Gd³⁺ and Y³⁺ on fluorescence intensity of the polynuclear complex Eu(TPA)(TTA)(TPPO)₂ was designed. The strong cofluorescence effect for the polynuclear complex Eu(TPA)(TTA)(TPPO)₂ can be obtained, when Gd³⁺,Y³⁺ions are added all together. The optimum total concentration of Gd³⁺ and Y³⁺ ions is 0.7 (molar fraction) The luminescent properties of the about nanostructured complexes Eu₂(TPA)(TTA)₄Phen₂ and Eu₂(TPA)(TTA)₄(TPPO)₄ were studied in detail. The results show that the about nanostructured complexes present stronger fluorescence intensity than their complex powders do. The main emission band of the about nanostructured complexes is sharper, but the split peak of the main emission band becomes weaker than their complex powders do. The about nanostructured complexes show weaker the cofluorescence effect of Gd(â…¢), whereas better luminescent properties in polyethylene plastic film than their complex powders do.Four europium(â…¢) complexes ofα-thenoyltrifluoroacetone with trimesic acid (TMA) or trimellitic acid (TLA) and phenanthroline, showing strong red fluorescence and good thermal stability, were synthesized. Their chemical structures proposed are the trinuclear for Eu₃(TMA)(TTA)₆Phen₃, Eu₃(TLA)(TTA)₆Phen₃ and the net polynuclear for Eu₃(TMA)₂(TTA)₃Phen₃, Eu₃(TLA)₂(TTA)₃Phen₃. The results of IR spectroscopy, scanning electronic microscopy and thermal analysis suggest the formation of the net polynuclear structure of the complexes Eu₃(TMA)₂(TTA)₃Phen₃ and Eu₃(TLA)₂(TTA)₃ Phen₃. The luminescent properties and luminescent lifetime values of the complexes Eu₃(TMA)(TTA)₆Phen₃ and Eu₃(TMA)₂ (TTA)₃Phen₃ had been measured in detail at room and liquid nitrogen temperature. The radiative (A_rad), non-radiative (A)(nrad)), the quantum efficiencies (η) of the emitting ⁵D₀ level and the values of the experimental intensity parameters (Ω_J) for the trimesic acid Eu(â…¢) complexes were calculated. The results show that two new complexes have long luminescent lifetimes, high quantum efficiencies and good thermal stability, and the Eu(â…¢) ion in two new complexes is in a site without a center of inversion. The Gd(â…¢) cofluorescence in trinuclear complex Eu₃(TMA) (TTA)₆Phen₃ was investigated in solids for the first time. The intra molecular energy transfer of the cross trinuclear is thought to be mainly responsible for the mechanism of the fluorescence enhancement of the trinuclear complexes. The cofluorescence mechanism of the trinuclear complexes has not been reported yet by now.The cofluorescence and thermal-optical stability of three types of Eu(â…¢) complexes were investigated. The results show that the cofluorescence and thermal-optical stability increase in the following order: the mononuclear complex, the binuclear complex, the polynuclear complex, which clearly establishes a correlation between the structure and the cofluorescence together with thermal-optical stability of the Eu(â…¢) complexes for the first time. The mechanism of cofluorescence of the above mentioned Eu(â…¢) complexes is preferably interpreted from the mononuclear, binuclear and polynuclear structure of these complexes. Intra molecular energy transfer in the cross polynuclear complexes is more efficient than intermolecular energy transfer between cross nuclear complex molecules. The systematic studies on the relationship between cofluorescence and the structure of the Eu(â…¢) complexes were not reported in the literatures.