| Fluorescence properties of rare earth organic complex have been widely applied in many fields, which has got more and more concerns. Fluorescence properties of rare earth complex are closely related to ligand structure, which are also influenced by the secondary ligand and the doped ions. In this work, the effects of energy level matching between rare earth ion and ligand, the synergism of the secondary ligand and ion doping on luminescence property of rare earth complex were investigated in detail. The research work mainly includes the following aspects:Triplet state energy levels of nine aromatic carboxylic acid ligands with different structures (L1(salicylic acid), L2(sulfosalicylic acid), L3(acetyl salicylic acid), L4(benzoic acid), L5(anthranilic acid), L6(N-phenyl anthranilic acid), L7(nitrobenzoic acid), L8(3-pyridyl acetic acid) and L9β-diketone (2-thiophene TTA) were calculated using Gaussian software. It is noted by comparison that the substituent groups greatly influenced the levels of triplet state energy. The energy level of the ligand with electron donating group increases,while the energy level of the ligand with electron withdrawing group decreases. In total, sixteen kinds of rare earth binary complexes of Tb3+, Eu3+ions with L1-L9ligands were synthesized, their composition and structure were characterized by chemical analysis, elemental analysis, ultraviolet spectrum, infrared spectroscopy, and their fluorescence intensities were compared and analyzed. Terbium binary complex with ligands of L2and L5has better fluorescence. The fluorescent characteristic peaks of Eu3+appear only on europium binary complexes with ligands of L4, L7and L9. The predicted fluorescence of binary rare earth complex in terms of calculated triplet state energy level of ligand according to level matching theory is consistent with experimental measurements.Fifty one kinds of ternary complexes of terbium and europium ions with L1-L9as the primary ligand, and10-phenanthroline (Phen), three phenyl phosphine oxide (TPPO) or8-hydroxyquinoline (Hoq) as the secondary ligand were synthesized respectively. The structure was characterized, and the fluorescence spectra were measured and synergistic effect of the secondary ligand on fluorescent property of complex was investigated in detail. Using ciprofloxacin (CIP), a class of quinolones drug,as ligand, binary and ternary drug rare earth complexes of terbrium(Ⅲ) ion and ciprofloxacin were synthesized. Their structure were characterized,and the influence of the secondary ligand on fluorescence property of the complex was studied.The secondary ligand could enhance fluorescent intensity, sensitize luminescence of rare earth ions in most cases.However, it could not enhance, or even weaken the fluorescence intensity of some complexes. The energy transfer process and luminescence mechanism of ternary complexes were discussed preliminarily from the perspective of energy matching according to the calculation results of triplet energy levels. The added secondary ligand changed the order of fluorescence intensity of the original binary terbium complex and the effect of the same secondary ligand on the luminescence property of the complexes with various primary ligand is different. Energy level of ligand L3poorly matches with the lowest excited state of (5D4) of Tb3+, which also has the weak UV absorption ability; but the fluorescence intensity of its corresponding ternary complex with ligand Phen increased hundreds times, exceeding that of Tb(L5)3Phen complex which has better energy match between L5ligand and Tb3+. When the energy gap between triplet state energy level of ligand and lowest excited energy of rare earth ion exceeds a certain range, the added secondary ligand can not enhance fluorescence intensity. The synergetic effect of the secondary ligand is closely related to itself structure and its energy level matching with central luminous ion, and is also related to the matching between the primary and secondary ligand; Appropriate level match between them can effectively improve the intramolecular energy transfer efficiency, consequently improving fluorescence of the complex.Because of their excellent fluorescence and dissolution filming, ternary terbium carboxylate complex of Tb(L8)3Phen and europiumβ-diketone complex of Eu(L9)3(TPPO)2was used as emitting layers to prepare the electroluminescent devices, and electroluminescent property were also measured. The results showed that both devices have excellent electroluminescent performance: long fluorescence lifetime and good monochromatic at lower voltage, which present a potential application prospect as green and red materials. Moreover, the thermal stability of Tb (L8)3Phen is better than that of Eu (L9)3(TPPO)2.High cost of rare earth ions as luminescent material limits its wider application to some extent. Metal ion-doping is not only another way to enhance fluorescence intensity, but also save costs by reducing amount of luminenscence ions. Using L6as the primary ligand and phen as the secondary ligand, Terbium complexes doped with rare earth ions (Eu3+, Sm3+, Dy3+, La3+, Gd3+, Y3+, Nd3+, Yb3+, Ho3+、Ce3+) and various transition metal and alkali metal ions (Cd2+, Zn2+, Co2+, Ni2+, Mn2+, Ca2+, Mg2+) were prepared by solvent-thermal method, respectively. Also, using L4and L7as the primary ligands and phen as the secondary ligand, europium complexes doped rare earth ions (Tb3+, Sm3+, Dy3+, La3+, Gd3+, Y3+, Nd3+, Yb3+, Ce3+、Ho3+) and transition metal and alkali metal ions (Cd2+, Zn2+, Co2+, Ni2+, Mn2+, Ca2+, Mg2+) were solvo-thermally synthesized, respectively. The effects of doped rare earth metal ions, transition metal ions and alkali metal ions on fluorescence properties of terbium and europium complexes and the property of those doped complexes were comparatively studied. Furthermore, the optimal doping amount of ions with the extensive fluorescence sensitization was explored, and energy transfer mechanism and fluorescence sensitization mechanism of the doped complex were investigated. Fluorescence sensitization law of doped metal ions was studied in perspective of nature of ligand and the radius gap between luminous rare earth ions and doped metal ions. Doped metal ions have different effects on the fluorescence intensity of different complex systems, the reason may be that their fluorescence sensitization could correlate to vibrational levels of doping ions, radius gap between doped ions and luminous rare earth ions, existing forms of doping ions in the complex and the properties of ligands as well. |
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