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  • Synthesis and characterization of the europium(III) pentakis(picrate) complexes with imidazolium countercations: structural and photoluminescence study.

Synthesis and characterization of the europium(III) pentakis(picrate) complexes with imidazolium countercations: structural and photoluminescence study.

Inorganic chemistry (2012-11-16)
Alex S Borges, José Diogo L Dutra, Ricardo O Freire, Renaldo T Moura, Jeferson G Da Silva, Oscar L Malta, Maria Helena Araujo, Hermi F Brito
ABSTRACT

Six new lanthanide complexes of stoichiometric formula (C)(2)[Ln(Pic)(5)]--where (C) is a imidazolium cation coming from the ionic liquids 1-butyl-3-methylimidazolium picrate (BMIm-Pic), 1-butyl-3-ethylimidazolium picrate (BEIm-Pic), and 1,3-dibutylimidazolium picrate (BBIm-Pic), and Ln is Eu(III) or Gd(III) ions--have been prepared and characterized. To the best of our knowledge, these are the first cases of Ln(III) pentakis(picrate) complexes. The crystal structures of (BEIm)(2)[Eu(Pic)(5)] and (BBIm)(2)[Eu(Pic)(5)] compounds were determined by single-crystal X-ray diffraction. The [Eu(Pic)(5)](2-) polyhedra have nine oxygen atoms coordinated to the Eu(III) ion, four oxygen atoms from bidentate picrate, and one oxygen atom from monodentate picrate. The structures of the Eu complexes were also calculated using the sparkle model for lanthanide complexes, allowing an analysis of intramolecular energy transfer processes in the coordination compounds. The photoluminescence properties of the Eu(III) complexes were then studied experimentally and theoretically, leading to a rationalization of their emission quantum yields.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Picric acid, moistened with water, ≥98%
Sigma-Aldrich
Picric acid solution
Sigma-Aldrich
Picric acid solution, 1.3% in H2O (saturated)
Supelco
Picric acid solution, 100 μg/mL in acetonitrile, PESTANAL®, analytical standard