Eu^III Luminescence in a Hygroscopic Ionic Liquid: Effect of Water and Evidence for a Complexation Process

Abstract

The spectroscopic characteristics (excitation, emission and lifetime) of EuIII dissolved in 1‐methyl‐3‐butylimidazolium bis(trifluoromethanesulfon)imide (BumimTf2N) are reported. In a first series of experiments, the effect of the presence of water in BumimTf2N was examined. It appears that non‐degassed solutions are most probably inhomogeneous, displaying large water clusters leading to an intense diffusion of the red light of an He:Ne laser. In these samples, the Eu emission spectrum is close to that observed in slightly acidic aqueous solutions. In contrast, when the samples were degassed the solution appeared homogeneous and water can be considered as a competitive ligand for the first coordination sphere of Eu. In a subsequent series of experiments, tetrabutylammonium chloride (TBACl) was added to the solution and the resultant species investigated. The ensuing enhancement in the metal‐centered luminescence has been interpreted in terms of changes in the inner coordination sphere of the EuIII ion and possible structures are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Speciation of Rare‐Earth Metal Complexes in Ionic Liquids: A Multiple‐Technique Approach

“…The presence of water in ionic liquids has to be carefully considered, because even traces of water strongly affect the luminescence properties, as has been shown for some lanthanides, drastically reducing the emission yield. [44] The solvation of f-block element metal ions in ionic liquids has been studied theoretically, for example, by means of molecular dynamics. [8,45,73] Ionic liquids have also been applied as extractants for f-block elements.…”

Why Use Ionic Liquids for Electrodeposition?

“…A similar scenario also exists with the incorporation of diluents or impurities and hence we need to define at what composition an ionic liquid is formed. Many ionic liquids with discrete anions are hydrophilic and the absorption of water is found sometimes to have a significant effect upon the viscosity and conductivity of the liquid [20][21][22]. Two recent approaches to overcome this difficulty have been to classify ionic liquids in terms of their charge mobility characteristics [23] and the correlation between the molar conductivity and fluidity of the liquids [24].…”

Lanthanides and Actinides in Ionic Liquids

“…59 65 Addition of chloride ligands resulted in the formation of different chloro species. The luminescence spectrum of the complex formed at high chloride concentrations is similar to the spectrum of [EuCl 6 ] 3-in ethanol.…”

“…67 The effects of water and added chloride ions on the spectra of Eu 3+ in the ionic liquid [C 4 mim][Tf 2 N] were studied. 65 Besides the crystal-field fine structure of the spectra, also the luminescence decay time can provide valuable information. For instance, the decay time of the excited state 5 D 0 of the Eu 3+ ion can be used to determine the number of water molecules that is directly coordinated to the Eu 3+ ion.…”