Crystal structure and Hirshfeld surface analysis of 3,6-bis(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazine dihydrate

In the crystal of the title compound, the packing is driven by O—H⋯O, O—H⋯N and N—H⋯N hydrogen-bond interactions along with π–π stacking interactions.


Supramolecular features
In the crystal, the H 2 bmtz molecules are stacked along [010] into columns throughinteractions between the pyrimidine rings [centroid-to-centroid distance = 3.726 (2) Å ]. At the same time, the water molecules are connected by O-HÁ Á ÁO hydrogen bonds (Table 1), resulting in the formation of a zigzag chain. These motifs are then connected together through N-HÁ Á ÁO hydrogen bonds involving the tetrazine nitrogen atoms and the water molecules to form a sheet structure propagating in the ab plane, as shown in Fig. 2. The sheets are further linked into an overall three-dimensional supramolecular network through N-HÁ Á ÁN hydrogen bonds with an R 2 2 (10) ring motif, Fig. 3, which involve the dihydro nitrogen atoms and the pyrimidine nitrogen atoms. A weak C-HÁ Á ÁO interaction is also noted ( Table 1).

Hirshfeld surface analysis
To further quantify the nature of the intermolecular interactions present in the crystal structure, Hirshfeld surfaces (McKinnon et al., 2007) and their associated two-dimensional fingerprint plots (Spackman & McKinnon, 2002) were generated using CrystalExplorer17 (Turner et al., 2017). The shorter and longer contacts are indicated as red and blue spots, respectively, on the Hirshfeld surfaces, and contacts with distances approximately equal to the sum of the van der Waals radii are represented as white spots. The contribution of interatomic contacts to the d norm surface of the title compound  Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
Partial packing diagram of (I), showing the O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds (dashed lines) andstacking interactions propagating in the ab plane.

Figure 3
Partial packing diagram of (I) viewed along the b axis, showing the N-HÁ Á ÁN hydrogen bonds (dashed lines).

Figure 1
Molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level. Unlabelled atoms are generated by the symmetry operation Àx, y, 3/2 À z.
is shown in Fig. 4. Analysis of the two-dimensional fingerprint plots, Fig. 4

Synthesis and crystallization
All commercially available chemicals and solvents were of reagent grade and were used as received without further purification. H 2 bmtz was synthesized according to a literature method (Kaim & Fees, 1995). Single crystals for X-ray struc-

3,6-Bis(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazine dihydrate
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.