Molecular structure of 8-hydroxy-1-methylquinolinium iodide hydrate in crystal and solution

8-Hydroxy-1-methylquinolinium iodide monohydrate [(C10H10NO)+I−·H2O] has been studied by X-ray diffraction, FT-IR, 1H and 13C NMR spectroscopy. In the crystalline state, the iodide anion is hydrogen-bonded to the water molecule, which in turn is hydrogen bonded to the 8-OH group of the 8-hydroxyquinolinium ring, forming of a symmetric dimer. In acetonitrile and DMSO-d6 the hydrate assumes a new structure due to almost complete dissociation of the water molecule from the complex structure. In acetonitrile the 8-OH group is hydrogen-bonded to the iodide anion, whereas in DMSO-d6 it forms the hydrogen bond with the solvent molecules. This 8-OH⋯O(DMSO-d6) hydrogen bond is the strongest within the structure of the hydrate.