The three-component cocrystal 1,3,5-trifluoro-2,4,6-triiodobenzene-pyridine N-oxide-water (1/2/1) built up by halogen bonds, hydrogen bonds and π-π interactions.

The title three-component cocrystal, C6F3I3·2C5H5NO·H2O, has been prepared as a strong candidate for multiple I...O interactions. Its crystal structure is compared with its 1:1 close relative, C6F3I3·C5H5NO [Aakeröy et al. (2014a). CrystEngComm, 16, 28-31]. The 1,3,5-trifluoro-2,4,6-triiodobenzene and water species both have crystallographic twofold axial symmetry. The main synthon in both structures is the π-π stacking of benzene rings, complemented by a number of O-H...O, C-F...π and, fundamentally, C-I...O interactions. As expected, the latter are among the strongest and more directional interactions of the sort reported in the literature, confirming that pyridine N-oxide is an eager acceptor. On the other hand, the structure presents only two of these contacts per 1,3,5-trifluoro-2,4,6-triiodobenzene molecule instead of the expected three. Possible reasons for this limitation are analyzed.