Speciation of uranyl complexes in ionic liquids by optical spectroscopy.
Uranyl complexes dissolved in room-temperature ionic liquids have diagnostic absorption and emission spectra which reflect the molecular symmetry and geometry. In particular, the characteristic vibrational fine structure of the absorption spectra allows identification of the molecular symmetry of a uranyl complex. The concept of speciation of uranyl complexes is illustrated for the hydrated uranyl ion, the tetrachloro complex [UO2Cl4]2-, the trinitrato complex [UO2(NO3)3]-, the triacetato complex [UO2(CH3COO)3]-, and the crown ether complex [UO2(18-crown-6)]2+ in imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids. The competition between 18-crown-6 and small inorganic ligands for coordination to the uranyl ion was investigated. The crystal structures of the hydrolysis product [(UO2)2(mu2-OH)2(H2O)6] [UO2Br4](18-crown-6)4 and imidazolium salt [C6mim]2[UO2Br4] are described.
Katholieke Universiteit Leuven, Department of Chemistry, Celestijnenlaan 200F bus 2404, B-3001, Leuven, Belgium.
Peter
P
Nockemann
Kelly
K
Servaes
Rik
R
Van Deun
Kristof
K
Van Hecke
Luc
L
Van Meervelt
Koen
K
Binnemans
Christiane
C
Görller-Walrand