Highly luminescent lanthanide complexes with novel bis-β-diketone ligand: Synthesis, characterization and photoluminescent properties

A biphenyl-linked bis-β-diketone ligand, 3,3′-bis(3-phenyl-3-oxopropanol)biphenyl (BPB) has been prepared for the syntheses of a series of dinuclear lanthanide complexes. The ligand bears two benzoyl β-diketonate sites linked by a 3,3’-biphenyl spacer. Reaction of the doubly negatively charged bis-bidenate ligand with lanthanide ions forms triple-stranded dinuclear complexes Ln2(BPB)3 (Ln = Nd (1), Sm (2), Eu (3), Yb (4) and Gd (5)). Electrospray mass spectrometry is used to identify the formation of the triple-stranded dinuclear complexes 1–5, which have been further characterized by various spectroscopic techniques. The complexes display strong visible and NIR luminescence upon excitation at ligands bands around 360 nm, depending on the choice of the lanthanides, and the emission quantum yields and luminescence lifetimes of 2–3 have been determined. It shows that the biphenyl-linked ligand BPB is a more efficient sensitizer than the monodiketone ligand DBM (dibenzoylmethane), through the comparisons of Ln2(BPB)3 and Ln(DBM)3 on their photoluminescent properties.

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► A bis-β-diketone ligand BPB has been prepared.
► A series of BPB lanthanide complexes have been prepared and characterized.
► The photoluminescent behaviors of BPB lanthanide complexes are investigated.
► Bis-β-diketone is more efficient to sensitize lanthanide than the mono-β-diketone.