Polythreading of 1-D sawtooth into 3-D ths net in the strong hydrogen-bonded supramolecular structure of 2-(1H-tetrazol-5-yl)pyrazine hemihydrate

Crystallization of tetrazole compound, 2-(1H-tetrazol-5-yl)pyrazine (TZP), from water gives rise to the 2:1 hydrate, TZP·(TZP·H₂O), with entangled structure involving two-dimensionally distinct strong hydrogen-bonded motifs of 1-D sawtooth chain and 3-D ths net (also called ThSi₂, (10, 3)-b net). In the former, TZP molecules link each other in an end-to-end mode by N{single bond}H⋯N(pyrazine) hydrogen bonds (C(6) synthon), while in the latter, both TZP and water molecules assemble through O{single bond}H⋯N(tetrazol), O{single bond}H⋯N(pyrazine) and N{single bond}H⋯O hydrogen bonds with each acting as a 3-connected node. There also exist weak hydrogen bonds of the C{single bond}H⋯N(tetrazol) between such 1-D chains and the 3-D net, and between adjacent chains, respectively. This result represents a rare example of hydrogen-bonded polythreading organic structure, and further exploits the using of tetrazole compound in hydrogen-bonded crystal engineering.