Synthesis, visible light absorption and luminescence of bipyrimidine bridged dinuclear lanthanide complexes of 2,4-pantanedione

New homodinuclear lanthanide-2,4-pantanedionate complexes of the type [(acac)3Ln(μ-bpm)Ln(acac)3] (acac is the anion of 2,4-pantanedione; bpm = 2,2′-bipyrimidine; Ln = Nd, Sm, Eu and Er) have been isolated by allowing, the coordinatively unsaturated Ln(acac)3 chelates to react with bpm, a bridging ligand, in 2:1 molar ratio in ethanol. Each lanthanide ion is eight-coordinate, in these dinuclear complexes, and is bound to six-O atoms of acac and two N-atoms of bridging bipyrimidine. The purity and homodinuclear nature of the complexes have been established by elemental analysis, NMR, and 4f–4f absorption spectroscopy. The NMR spectra and oscillator strength of the hypersensitive transitions of the complexes confirm the presence of two metals in the complex joined by the bridging bpm ligand. The complexes of Sm and Eu display pink and brilliant-red luminescences, respectively. The intramolecular Eu–Eu energy transferred has been observed in the europium complex.