1,2,4-Oxadiazole Ring as the Halogen-Bond Acceptor: The Case Study of Dibenzoiodolium 1,2,4-Oxadiazolates

Three dibenzoiodolium 3-aryl-1,2,4-oxadiazolates (4a–c) were synthesized and characterized by 1H and 13C{H} NMR as well as HRMS in both positive and negative modes. The solid-state structures of these compounds were determined by X-ray diffraction. Two of them were obtained as isostructural monohydrates (4a·H2O and 4b·H2O), whereas the third structure (4c) represents a monocomponent system. In the case of 4c, the I···N halogen bonding (HaB) involving the N4 atom of the heterocyclic anion was identified, which is the first report on the 1,2,4-oxadiazole ring acting as a HaB acceptor. Moreover, in all structures, strong I···O HaBs between the iodine(III) center and the exocyclic oxygen atom of the 1,2,4-oxadiazolate anion were revealed, including the rare example of the bifurcate I···(O,O) HaB with two different anions (4c). DFT calculations using periodic boundary conditions confirmed the existence and the nature of these interactions.