Photoluminescence properties of dinuclear lanthanide complexes in visible and near-infrared region

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.