Utilizing sulfoxide•••iodine halogen bonding for cocrystallization

The propensity of a range of different sulfoxides and sulfones to cocrystallize with either 1,2- or 1,4-diiodotetrafluorobenzene, via I•••O=S halogen bonding, was investigated. Cocrystallization occurred exclusively with 1,4-diiodotetrafluorobenzene in either a 1:1 or 1:2 stoichiometry of the organohalide and the sulfoxide, respectively, depending on the sulfoxide used. It was found that the stoichiometry observed was not necessarily related to whether the oxygen acts as a single halogen bond acceptor or if it is bifurcated; with I•••π interactions observed in two of the cocrystals synthesized. Only those cocrystals with a 1:2 stoichiometry exhibit C-H•••O hydrogen bonding in addition to I•••O=S halogen bonding. Examination of the Cambridge Structural Database shows that (i) the I•••O=S interaction is similar to other I•••O interactions, and (ii) the I•••π interaction is significant, with the distances in the two cocrystals among the shortest known.