Pyrazine bridged Ln2 (La, Nd, Eu and Tb) complexes containing fluorinated β-diketone

Pyrazine bridged dinuclear lanthanide β-diketonate complexes of the type [(tfaa)3Ln(μ-pyz)Ln(tfaa)3] (tfaa is the anion of 1,1,1-trifluoro-2,4-pentanedione; pyz is pyrazine) were isolated by mixing [Ln(tfaa)3] and pyrazine in 2:1 molar ratio in chloroform. The elemental analysis, high yield and only one sharp resonance for the pyrazine moiety in the NMR spectrum are strong enough to support dinuclear complex formation. The oscillator strength of the hypersensitive 4G5/2, 2G7/2 ← 4I9/2 transition of the neodymium complex is approximately two fold higher than the mononuclear [Nd(tfaa)3H2O]. It confirms the presence of two neodymium ions both of which contribute to the oscillator strength. The red and green photoluminescence of Eu–Eu and Tb–Tb complexes, respectively, were scrutinized in solution and discussed.