Influence of Elemental Iodine on Imidazolium-Based Ionic Liquids: Solution and Solid-State Effects

Ionic liquids doped with I2, usually resulting in the formation of polyiodide anions, are extensively
used as electrolytes and in iodination reactions. Herein, NMR spectroscopy
and single-crystal X-ray diffraction were used to rationalize the
structures of imidazolium-based polyiodide ionic liquids in the liquid
and solid states. Combined, these studies show that extensive interactions
between the imidazolium cation and the resulting polyiodide anion
are present, which have the net effect of lengthening, polarizing,
and weakening the I–I bonds in the anion. This bond weakening
rationalizes the high conductivity and reactivity of ionic liquids
doped with I2.