Synthesis and fluorescence properties of doped europium benzene-1, 3, 5-tricarboxylate complexes

Nine doped europium benzene-1, 3, 5-tricarboxylate complexes have been synthesized and characterized. Elemental analysis, rare earth coordination titration, IR spectra, UV absorption spectra and TG-DTA were used to characterized these complexes. The studies of the fluorescence spectra and lifetimes of the nine complexes show obviously difference. Compared with binary complex of EuL &middot 6H2O(1), the ternary complex EuLL'1.5 &middot 2H2O exhibits stronger luminescence intensity. This result indicates that the fluorescence intensities of the complexes depend on ligands. In the binary complex the ligand (btc) transfers some energy to Eu3+, but in ternary complexes both the ligands (btc and phen) transfer more energy. The fluorescence peak positions of the other seven are similar to (1) and (2), but the luminescence intensities of these complexes are obviously different. The positions of Eu3+ emission peak of the complexes do not change, indicating that the introduction of doped rare earth ions or transition-metal ions does not influence the energy level of Eu3+ in the complexes. The dinuclear complexes, which contain the metal ions Y3+, La3+, Zn2+ and Cd2+ without unsa-turated d-layer or f-layer electrons, display sensitization and strengthening to fluorescence properties of those complexes, respectively. Therefore, the energy absorption by organic ligands will not be consumed by the d-d or f-f transfer. In this manner, Eu3+ absorbs much more energy through intramolecular energy transfer and luminous intensity is enhanced. Gd3+ has inert half-full 4f7 electronic configuration, so the luminous intensity of (5) is also strong and similar with (3) and (4). Complexes (8) and (9), containing Mn2+ and Ni2+, respectively, exhibit fluorescence quenching, which is caused by the unsaturated d-layer electrons consuming the energy in the form of radiative transition.EI06920-9253