Synthesis and photoluminescent properties of five homodinuclear lanthanide (Ln3+ = Eu3+, Sm3+, Er3+, Yb3+, Pr3+) complexes

A series of homodinuclear lanthanide complexes Ln2(HTH)6Bpm (where Ln = Eu, Sm, Er, Yb, Pr; HTH = 4,4,5,5,6,6,6-heptafluroro-1-(2-thienyl)hexane-1,3-dione; Bpm = 2,2′-bipyrimidine) were synthesized and the photoluminescence properties of these complexes are described. After ligand-mediated excitation of the complexes, they all show the characteristic luminescence of the corresponding Ln3+ ions in the visible and NIR regions attributed to efficient energy transfer from the ligands to the metal centres. For the Eu2(HTH)6Bpm complex a lifetime of 738.8 μs (100%, χ2 = 1.362) is found in solid and two lifetimes of 455.4 μs (12.88%) and 618.5 μs (87.12%) (χ2 = 1.652) are found in CH2Cl2 solution, respectively. Its quantum efficiency in air-equilibrated CH2Cl2 solution is found to be 28.4%, by using air-equilibrated aqueous [Ru(bpy)3]2+·2Cl− solution as reference sample (Φstd = 2.8%).