A dinuclear Eu(Ⅲ) complex Eu2(DBM)6TPPD (Hexa(dibenzoyl-methanido)-(N, N, N, N-tetra(2-pyridyl)-1, 4-phenylenediamine)-dieuropium(Ⅲ)) was synthesized by employing DBM (dibenzoylmethane) and TPPD (N, N, N, N-Tetra(2-pyridyl)-1, 4-phenyl-enediamine) as sensitizing ligands for the Eu(Ⅲ) ion and a bridging ligand, respectively. The analysis of the absorption, excitation, and emission spectra of the dinuclear complex along with a comparison with analogous mononuclear complex containing the same β-diketone ligands and 1, 10-phenanthroline (phen) suggests that the dinuclear complex follows the luminescence mechanism of general Ln(Ⅲ) complexes.
Several dinuclear lanthanide complexes of Ln2(HTH)6TPPHZ (Ln=Eu, Sm, Er, Nd, Yb, Ho; TPPHZ=Tetrapyrido (3,2-a:2',3'-c:3',2"-h:2"',3'"-j) phenazine; HTH=4,5,5,6,6,6-heptafluroro-1-(2-thienyl)hexane-1,3-dione were synthesized and their photoluminescence properties were investigated. After ligand-mediated excitation, all the complexes showed the characteristic luminescence of the corresponding Ln(III) ions in the visible and NIR regions attributed to energy transfer from the ligands to the metal center. For Eu2(HTH)6TPPHZ complex, the quantum efficiency was calculated as 9.6% with the major 5D0 lifetime (477.86 μs) by the equation Φ=τobs/τR, where τobs was observed luminescence lifetime and τR was radiative (or natural) lifetime (5 ms), and 14.9% with air-equilibrated aqueous [Ru(bpy)3](II)·2Cl- solution as a standard sample (Φstd=2.8%), in CH2Cl2 solution at room temperature.
A novel dendritic europium complex containing grafted carbazole units as functional peripheries was synthesized and character- ized. The Frster energy transfer from the peripheries of carbazole units to β-diketonate as well as from the ligands to the central Eu(III) ions in the complex was demonstrated. Under the excitation of carbazole units and β-diketonate, characteristic red emission peaks at 612 nm with four shoulders due to the Eu(III) ion transition of 5D0→7FJ (J=0-4) were observed for the complex.
