Abstract
The structure-directing "key-to-lock" interaction of double σ-(I(III))-hole donating iodonium cations with the O-flanked pseudo-lacune rims of [β-Mo(8)O(26)](4-) gives halogen-bonded iodonium-beta-octamolybate supramolecular associates. In the occurrence of their tetragonal pyramidal motifs, deep and broad σ-(I(III))-holes of a cation recognize the molybdate backbone, which provides an electronic pool localized around the two lacunae. The halogen-bonded I⋯O linkages in the structures were thoroughly studied computationally and classified as two-center, three-center bifurcated, and unconventional "orthogonal" I⋯O halogen bonds. In the latter, the O-atom approaches orthogonally the C-I(III)-C plane of an iodonium cation and this geometry diverge from the IUPAC criteria for the identification of the halogen bond.