Electrochemical Survey of Ln³⁺ (Ln = Dy, Er, Gd, Ho, Tb, Tm) in a Bis(trifluoromethylsulfonyl)imide-Based Room-Temperature Ionic Liquid with and without Added Chloride Ion

Electrochemical measurements were used to probe the solvation by chloride and the accessible oxidation states of Dy, Er, Gd, Ho, Tb, and Tm in a room-temperature ionic liquid (RTIL) based on the 1-ethyl-3-methylimidazolium cation (EtMeIm + ) and the bis(trifluoromethylsulfonyl)amide anion (Tf 2 N − ). Controlled potential coulometry indicated that all these lanthanide (Ln) metals were oxidized into the RTILs as the corresponding Ln 3+ species. Amperometric titration experiments with added Cl − revealed that this anion coordinates with each Ln 3+ to form a likely octahedral complex represented as [LnCl 6 ] 3− . Of the Ln 3+ solutions that were prepared by CPC, cyclic staircase voltammetry indicated that only Tm 3+ exhibited electrochemical activity within the potential window of the solvent. Thus, we report here the first electrochemical investigation of the Tm 3+/2+ reaction in an anhydrous low melting ionic liquid. The reduction of Tm 3+ to Tm 2+ is complicated by the disproportionation of the Tm 2+ to Tm 3+ and Tm 0 . The latter appears to react with the ionic liquid cation.