Imidazolium-based, sulfonate functionalized zwitterions and ionic liquids with different alkyl chain side lengths for Cu electrodeposition.
Selflando SHEHAJ1, Andreas TAUBERT1
1University of Potsdam, Potsdam, Germany
The properties of ionic liquids (ILs) depend, among others, on the alkyl chain length attached to the cationic core. We have synthesized a new series of zwitterions [1-alkyl-3-(4-sulfobutyl)-imidazolium] zwitterions and zwitterionic [1-alkyl-3-(4-sulfobutyl)-imidazolium][methanesulfonate] ILs. The alkyl chains used in this study are methyl, ethyl, butyl, hexyl, benzyl, octyl, decyl, and dodecyl. All reactions were solvent-free, and the resulting products were white to off-white solids or oils. The products were characterized using thermogravimetric analysis, differential scanning calorimetry, cyclic voltammetry, NMR, ATR-IR, single crystal analysis, polarization optical microscopy, impedance spectroscopy, and theoretical calculations.
Zwitterions with alkyl chains ranging from C1-C7 are fine white powders, while compounds with alkyl chain lengths from C8-C10 are transparent, highly viscous liquids at room temperature; C12 zwitterion initially is a transparent, highly viscous liquid but solidifies over time. Some zwitterions show liquid crystalline phases, and most are relatively stable thermally. The resulting ILs are liquid at room temperature except [1-decyl-3-(4-sulfobutyl)-imidazolium][MeSO3] and [1-decyl-3-(4-sulfobutyl)-imidazolium][MeSO3] which are solid. Generally, ILs showed superiority in thermal and electrochemical properties.
The ILs effectively dissolve CuO, and the Cu can then readily be electrodeposited again from the Cu(II)/IL solutions.