title: Synthesis and characterization of the europium(III) pentakis(picrate) complexes with imidazolium countercations: structural and photoluminescence study.
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.
authors.affiliation: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte-MG, 31270-901, Brazil.
authors.forename: Alex S
authors.initials: AS
authors.lastname: Borges
authors.forename: José Diogo L
authors.initials: JD
authors.lastname: Dutra
authors.forename: Ricardo O
authors.initials: RO
authors.lastname: Freire
authors.forename: Renaldo T
authors.initials: RT
authors.lastname: Moura
authors.forename: Jeferson G
authors.initials: JG
authors.lastname: Da Silva
authors.forename: Oscar L
authors.initials: OL
authors.lastname: Malta
authors.forename: Maria Helena
authors.initials: MH
authors.lastname: Araujo
authors.forename: Hermi F
authors.initials: HF
authors.lastname: Brito
mesh_terms: D018360:Crystallography, X-Ray; D005063:Europium / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D008163:Luminescent Measurements; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010851:Picrates / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D009942:Organometallic Compounds; D010851:Picrates; D005063:Europium; C005858:picric acid