Electrochemical and Spectroscopic Investigation of Ln3+ (Ln = Sm, Eu, and Yb) Solvation in Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids and Coordination by N,N,N′,N′-Tetraoctyl-3-oxa-pentane Diamide (TODGA) and Chloride

The electrochemistry and electronic absorption spectroscopy of samarium, europium, and ytterbium were investigated in the 1-(1-butyl)trimethylammonium bis(trifluoromethylsulfonyl)imide (BuMe3NTf2N) and 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyroTf2N) ionic liquids and in these solvents containing the neutral tridentate ligand N,N,N′,N′-tetraoctyl-3-oxo-pentane diamide (TODGA) and the anionic hard ligand chloride. Lanthanide ions were introduced into the ionic liquids by controlled potential oxidation of the respective metals to yield solutions containing Eu2+, Sm3+, and Yb3+, and it was possible to cycle between Eu2+ and Eu3+ as well as Yb3+ and Yb2+ using controlled potential electrolysis. Electronic absorption spectroscopy suggested that the Ln3+ species are weakly solvated by Tf2N– anions as [Ln(Tf2N)x](x−3)– in the neat ILs. The quasireversible Ln3+/2+ couples of all three elements were readily accessible in these ILs, but Sm2+ was only stable on the voltammetric time sca...