Crystal structure and highly luminescent properties studies of bis-β-diketonate lanthanide complexes

A new bis(β-diketonate), 1,3-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenyl (BTP), which contains a trifluorinated alkyl group, has been prepared for the synthesis of two series of dinuclear lanthanide complexes with the general formula Ln2(BTP)3L2 [Ln(3+) = Eu(3+), L = DME(1), bpy(2), and phen(3); Ln(3+) = Sm(3+), L = DME(4), bpy(5), and phen(6); DME = ethylene glycol dimethyl ether, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline]. The crystal structure of the free ligand has been determined and shows a twisted arrangement of the two binding sites around the 1,3-phenylene spacer. X-ray crystallographic analysis reveals that complexes 1, 2, 4, and 5 are triple-stranded dinuclear structures formed by three bis-bidentate ligands with two lanthanide ions. The room-temperature photoluminescence (PL) spectra of complexes 1-6 show that this bis-β-diketonate can effectively sensitize rare earths (Sm(3+) and Eu(3+)) and produce characteristic emissions of the corresponding Eu(3+) and Sm(3+) ions. In addition, two bidentate nitrogen ancillary ligands, 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), have been employed to enhance the luminescence quantum yields and lifetimes of both series of Eu(3+) and Sm(3+) complexes.