Solvation structure of a copper(II) ion in protic ionic liquids comprising N-hexylethylenediamine.

The fine and dynamic structure of the copper(II) ion solvated in a protic ionic liquid (PIL) comprising monoprotonated N-hexylethylenediaminium (HHexen(+)) and bis(trifluoromethanesulfonyl)amide (Tf2N(-)) [or trifluoroacetate (TFA(-))] was determined using NMR, visible electronic, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The chelate-diamine group in the cationic unit facilitates advantageous dissolution of transition-metal salts in the present PIL. The interaction of the copper(II) ion with the chelate-diamine PIL was explored by the addition of copper(II) salts to the PIL, demonstrating competitive complexation between the ligand of the added copper(II) salt and the components of the ionic liquid to the copper(II) ion.