The compounds [H3O(dibenzo-18-crown-6)][Ix] (x = 3,5,7) have been synthesised and investigated by X-ray diffraction as well as Raman and far-IR spectroscopy. The structure of the triiodide contains two independent, slightly asymmetric and bent I3− ions with I–I distances in the range 2.92–2.94 Å. The pentaiodide can be described as composed of (I3−)·I2, where the I–I distances in the asymmetric and slightly bent I3 unit are 2.894(2) and 2.942(2) Å and in the I2 unit 2.763(2) Å. The L-shaped I5− ions are linked together forming a chain of I10 rectangles through van der Waals interactions in the range 3.7–3.8 Å. The structure determination supports a pyramidal geometry of the H3O+ ion in the dibenzo-18-crown-6 moiety of both structures. Because of severe crystal twinning the crystal structure of the heptaiodide could not be determined. However, the results from the spectroscopic investigation are consistent with a heptaiodide of composition (I3−)·2I2.
