Luminescent Binuclear Eu(III) and Tb(III) Complexes Based on 3,6-bis(Diphenylphosphinyl)Pyridazine

Isostructural binuclear complexes [Ln 2 L 2 (hfac) 6 ] (Ln = Eu, Tb; hfac – = hexafluoroacetylacetonate ion) are synthesized by the interaction of [Ln(hfac) 3 (H 2 O) 2 ] with 3,6-bis(diphenylphosphinyl)pyridazine (L). According to the single-crystal XRD data, two Ln(hfac) 3 moieties in the complexes are connected by two O,O´-bidentate-bridging ligands L, and the coordination polyhedron Ln@O 8 has the geometry of a triangular dodecahedron. The Eu 3+ and Tb 3+ complexes exhibit characteristic lanthanide-centered photoluminescence in the solid state at 297 K with luminescence quantum yields of 31% and 2% and excited state lifetimes of 707 and 30 μs, respectively, thus indicating that luminescence sensitization by the ligand environment is more effective for Eu 3+ than for Tb 3+ .