Synthesis And Luminescent Study Of Novel Lanthanide Complexes With N, O Synergistic Chelating Ligands

In order to develop highly luminescent lanthanide complexes with excellent charge transporting properties, four new types of ligands with synergistic coordinated nitrogen and oxygen atoms were synthesized and used as sensitizers for rare earth ions luminescence. The contents are as follows:1. Synthesis and luminescent properties of europium complexes with imide derivatives containing synergistic coordinated nitrogen and oxygen atoms(1) For the advantages of oxadiazole-functionalized imide ligands which containing synergistic coordinated nitrogen and oxygen atoms and large delocalized conjugated system, a series of new oxadiazole-functionalized imide derivatives HL1-HL5 were synthesized. The photophysical properties of those binary europium complexes Eu(Ln)3(H2O)2 (n= 1-5) were thoroughly investigated. The results show that:(i) This kind of ligands have high optical absorption coefficient and could be used as good antennas for sensitizing Eu3+ luminescence. (ii) The singlet and triplet energy levels of the oxadiazole-functionalized ligands can be fine tuned by introducing substituents with different electronic properties to match the 5D0 energy level of Eu3+. (iii) The complex Eu(L3)3(phen) was synthesized by introducing the neutral ligand of 1,10-phenanthroline. Using Eu(L3)3(phen) as the emitting material, an electroluminescent device was fabricated. The device emits pure red light with the maximum luminance of 117 cd/m2 and the maximum power efficiency of 0.17 lm/W.(2) A new type of tridentate neutral ligands (N-(1,10-phenanthrolin-9-yl) aromatic-amide derivatives) A1-A6 were synthesized, and their europium complexes Eu(NO3)3(An) and Eu(Pic)3(An)2·CH3CH2OH (n= 1,2,3,4,6) with NO3-and picrate (Pic-) as anion were also synthesized and characterized by UV-Vis, IR and crystal structure analysis. The results show that these neutral ligands are coordinated with europium(III) by tridentate coordination mode. The photophysical studies demonstrated that this kind of ligands have high optical absorption coefficient and suitable triplet energy levels to match the 5D0 energy level of Eu3+. Therefore, these ligand could be used as good antennas for sensitizing Eu3+ luminescence. The fluorescence lifetimes and quantum efficiencies of pi crate-based europium complexes are much smaller than those of nitro-based due to the existence of -OH in the inner coordination sphere and charge-transfer state of Pic-.2. Synthesis and near-infrared luminescence properties of rare earth complexes with 1,10-phenanthroline derivatives containing synergistic coordinated nitrogen and oxygen atoms(1) A series of lanthanide(Er3+, Nd3+, Yd3+) complexes containing 2-(1,10-phenanthroline-yl)-2-phenol compounds(HN1 and HN2) were synthesized, and their photophysical properties were carefully studied. This kind of ligands could be used as good antenna because of their high optical absorption coefficient in the range of 210～450 nm. The complexes show the characteristic emission of Neodymium, Erbium and Ytterbium ions in the near-infrared region with 420 nm excitation. The luminescent decay curves of Neodymium and Ytterbium complexes fit monoexponential functions, which suggests that in each complex the coordination site of Eu3+ is unique. We found that the uncoordinated OH oscillators of ligand HN2 could quench the fluorescent emission to some extent. The triplet energy levels of ligands HN1 and HN2 are 16584 cm-1 and 17065cm-1, respectively, which perfectly match the excited level of Nd3+, Er3+ and Yb3+(2) A new series of 2-(1,10-phenanthrolin-2-yl)-1-aromaticethanone derivatives HF1-HF6 and their Neodymium, Erbium and Ytterbium complexes Nd(Fn)3, Er (Fn)3 and Dy(Fn)3 (n= 1～6) were synthesized and characterized by UV-Vis, IR and photo-physical studies. The results show that:(i) This kind of ligands with high optical absorption coefficient could be used as sensitizer for Er3+, Nd3+, Yd3+ ions. (ii) The long fluorescence lifetimes of Neodymium and Ytterbium complexes with HF6 was due to the reduced high frequency vibration of CH by introducing -CF3 subsistent. (iii) The triplet energy levels of ligands HF1—HF6 match the excited level of Nd3+, Er3+ and Yb3+ perfectly, which make them good sensitizers for near-infrared luminescence of rare earth complexes.(3) The quantum chemistry calculation on ligands A1 and HF1 was studied at B3LYP/6-31G and TD-B3LYP/6-31G level and the front molecular orbital and excited state energy level were systemically analyzed. The calculation results show that the different contribution of every parts of ligand to the front molecular orbital and the direction of electronic transition from ground state to the excited state cause the very large difference between their triplet energy levels. The sensitization mechanism of A1 and F1 for different rare earth ions could be clearly elucidated from the point of view of quantum chemistry.