title: Speciation of rare-earth metal complexes in ionic liquids: a multiple-technique approach.
abstract: The dissolution process of metal complexes in ionic liquids was investigated by a multiple-technique approach to reveal the solvate species of the metal in solution. The task-specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf(2)N]) is able to dissolve stoichiometric amounts of the oxides of the rare-earth elements. The crystal structures of the compounds [Eu(2)(bet)(8)(H(2)O)(4)][Tf(2)N](6), [Eu(2)(bet)(8)(H(2)O)(2)][Tf(2)N](6) x 2 H(2)O, and [Y(2)(bet)(6)(H(2)O)(4)][Tf(2)N](6) were found to consist of dimers. These rare-earth complexes are well soluble in the ionic liquids [Hbet][Tf(2)N] and [C(4)mim][Tf(2)N] (C(4)mim = 1-butyl-3-methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, (1)H, (13)C, and (89)Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X-ray absorption fine structure) and HEXS (high-energy X-ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry.
authors.affiliation: Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F bus 2404, 3001 Leuven, Belgium. peter.nockemann@chem.kuleuven.be
authors.forename: Peter
authors.initials: P
authors.lastname: Nockemann
authors.forename: Ben
authors.initials: B
authors.lastname: Thijs
authors.forename: Kyra
authors.initials: K
authors.lastname: Lunstroot
authors.forename: Tatjana N
authors.initials: TN
authors.lastname: Parac-Vogt
authors.forename: Christiane
authors.initials: C
authors.lastname: Görller-Walrand
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Hecke
authors.forename: Luc
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: Sergey
authors.initials: S
authors.lastname: Nikitenko
authors.forename: John
authors.initials: J
authors.lastname: Daniels
authors.forename: Christoph
authors.initials: C
authors.lastname: Hennig
authors.forename: Rik
authors.initials: R
authors.lastname: Van Deun