Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X ] , [XY ] , and [BrF ] (X=Cl, Br, I and Y=Cl, Br).

The ionic liquid (IL) trihalogen monoanions [N ][X ] and [N ][XY ] ([N ] =triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1-butyl-1-methyl-pyrrolidinium trifluoromethane-sulfonate ([BMP][OTf], [X ] /[XY ] 0.5 M). Lighter IL trihalogen monoanions displayed higher conductivities than their heavier homologues, with [Cl ] being 1.1 and 3.7 times greater than [Br ] and [I ] , respectively. The addition of [BMP][OTf] reduced the conductivity significantly. Within the group of polyhalogen monoanions, the oxidation potential develops in the series [Cl ] >[BrCl ] >[Br ] >[IBr ] >[ICl ] >[I ] . The redox potential of the interhalogen monoanions was found to be primarily determined by the central halogen, I in [ICl ] and [IBr ] and Br in [BrCl ] . Additionally, tetrafluorobromate(III) ([N ] [BrF ] ) was analyzed via CV in MeCN at 0 °C, yielding a single reversible redox process ([BrF ] /[BrF ] ).