In the title monohydrated cocrystal, namely 1,3-diamino-5-azaniumyl-1,3,5-trideoxy-cis-inositol iodide-1,3,5-triamino-1,3,5-trideoxy-cis-inositol-water (1/1/1), C6H16N3O3(+)·I(-)·C6H15N3O3·H2O, the neutral 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) molecule and the monoprotonated 1,3-diamino-5-azaniumyl-1,3,5-trideoxy-cis-inositol cation (Htaci(+)) both adopt a chair conformation, with the three O atoms in axial and the three N atoms in equatorial positions. The cation, but not the neutral taci unit, exhibits intramolecular O-H···O hydrogen bonding. The entire structure is stabilized by a complex three-dimensional network of intermolecular hydrogen bonds. The neutral taci entities and the Htaci(+) cations are each aligned into chains along [001]. In these chains, two O-H···N interactions generate a ten-membered ring as the predominant structural motif. The rings consist of vicinal 2-amino-1-hydroxyethylene units of neighbouring molecules, which are paired via centres of inversion. The chains are interconnected into undulating layers parallel to the ac plane, and the layers are further held together by O-H···N hydrogen bonds and additional interactions with the iodide counter-anions and solvent water molecules.
Keywords: 1,3,5-triamino-1,3,5-trideoxy-cis-inositol; amine–alcohol hydrogen bonding; asymmetric bifurcation; crystal structure; polyamino-polyalcohols.