Interaction of thiamine with anions in the triclinic form of thiamine iodide: 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-hydroxyethyl)-4-methyl-1,3-thiazol-3-ium iodide 1.25-hydrate

The asymmetric unit of the title compound, C12H17N4OS+center dot I-center dot 1.25H(2)O, contains two crystallographically independent molecules. Both formula units assume the usual F conformation and have the hydroxyethyl group disordered over two sites, each with half occupation. Two thiamine cations are linked by hydrogen bonds into a cyclic dimer. These dimers are further connected by base-pairing hydrogen bonds into a chain along [010]. The stacked dimers form channels, which are occupied by iodide anions. The cations and anions are associated by N-H center dot center dot center dot I hydrogen bonds, C-H center dot center dot center dot I interactions and I center dot center dot center dot thiazolium ring close contacts. The interactions between thiamine and the iodide anions are similar to those observed in monoclinic thiamine iodide 1.5-hydrate [Hu & Zhang (1993). J. Inclusion Phenom. Mol. Recognit. Chem. 16, 273-281].