title: Uranyl complexes of carboxyl-functionalized ionic liquids.
abstract: Uranium(VI) oxide has been dissolved in three different ionic liquids functionalized with a carboxyl group: betainium bis[(trifluoromethyl)sulfonyl]imide, 1-(carboxymethyl)-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and N-(carboxymethyl)-N-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide. The dissolution process results in the formation of uranyl complexes with zwitterionic carboxylate ligands and bis[(trifluoromethyl)sulfonyl]imide (bistriflimide) counterions. An X-ray diffraction study on single crystals of the uranyl complexes revealed that the crystal structure strongly depends on the cationic core appended to the carboxylate groups. The betainium ionic liquid gives a dimeric uranyl complex, the imidazolium ionic liquid a monomeric complex, and the pyrrolidinium ionic liquid a one-dimensional polymeric uranyl complex. Extended X-ray absorption fine structure measurements have been performed on the betainium uranyl complex. The absorption and luminescence spectra of the uranyl betainium complex have been studied in the solid state and dissolved in water, in acetonitrile, and in the ionic liquid betainium bistriflimide. The carboxylate groups remain coordinated to uranyl in acetonitrile and in betainium bistriflimide but not in water.
authors.affiliation: The QUILL Research Centre, School of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Nockemann
authors.forename: Rik
authors.initials: R
authors.lastname: Van Deun
authors.forename: Ben
authors.initials: B
authors.lastname: Thijs
authors.forename: Diederik
authors.initials: D
authors.lastname: Huys
authors.forename: Evert
authors.initials: E
authors.lastname: Vanecht
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Hecke
authors.forename: Luc
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans