Acylpyrazolonate-based lanthanide complexes: Synthesis, crystal structures and photoluminescence properties

Two new acylpyrazolonate-based lanthanide complexes of formula [Ln(pmap)3(H2O)2]·CH3COOC2H5 (Ln = Tb 1, Eu 2 and pmap = 1-phenyl-3-methyl-4-acetyl-5-pyrazolonate) have been prepared and characterized by X-ray single crystal determination and spectroscopic methods. The crystal structure analysis reveals that 1 and 2 are isostructural and crystallize in the triclinic space group P 1 ¯ with two independent, but structurally similar molecules in the structural unit, which are exceptionally rare in acylpyrazolonate-based mononuclear lanthanide complexes. In CH3CN solution, the photoluminescence investigation demonstrates that 1 displays intensely green emission of Tb(III)-centered, while Eu(III)-complex does not emit characteristically red luminescence. The results are elucidated in terms of the energy gap ΔE(3ππ*–5D4 or 5D0) between Hpmap ligand and resonance levels of Tb(III) or Eu(III) ion.