4-(Pyrimidin-2-yl)piperazin-1-ium (E)-3-carboxyprop-2-enoate

In the cation of the title salt, C8H13N4 +·C4H3O4 −, the piperazinium ring adopts a slightly distorteded chair conformation. In the crystal, a single strong O—H⋯O intermolecular hydrogen bond links the anions, forming chains along the c-axis direction. The chains of anions are linked by the cations, via N—H⋯O hydrogen bonds, forming sheets parallel to (100). These layers are linked by weak C—H⋯O hydrogen bonds, forming a three-dimensional structure. In addition, there are weak π–π interactions [centroid–centroid distance = 3.820 (9) Å] present involving inversion-related pyrimidine rings.

In the cation of the title salt, C 8 H 13 N 4 + ÁC 4 H 3 O 4 À , the piperazinium ring adopts a slightly distorteded chair conformation. In the crystal, a single strong O-HÁ Á ÁO intermolecular hydrogen bond links the anions, forming chains along the c-axis direction. The chains of anions are linked by the cations, via N-HÁ Á ÁO hydrogen bonds, forming sheets parallel to (100). These layers are linked by weak C-HÁ Á ÁO hydrogen bonds, forming a three-dimensional structure. In addition, there are weakinteractions [centroid-centroid distance = 3.820 (9) Å ] present involving inversion-related pyrimidine rings.

Comment
Pyrimidine derivatives have attracted organic chemists due to their biological and chemotherapeutic importance. Related fused heterocycles are important classes of heterocyclic compounds that exhibit a broad spectrum of biological activities such as anticancer (Amin et al., 2009;Pandey et al., 2004), antiviral (Ibrahim & El-Metwally, 2010), antibacterial (Kuyper et al., 1996), antioxidant (Padmaja et al. , 2009), antidepressant (Kim et al., 2010) and anti-inflammatory (Clark et al., 2007). Piperazine-based compounds have been employed as antibacterial, antidepressant, and antitumor drugs, and as α adrenoceptor antagonists, CCR5 receptor antagonists, 5-HT7 receptor antagonists, and adenosine A2a receptor antagonists (Abdel-Jalil et al., 2010). Several piperazine derivatives have reached the stage of clinical application among the known drugs that are used to treat anxiety including the pyrimidinyl piperazinyl compounds, buspirone and BuSpar (Tollefson et al., 1991). The incorporation of two moieties increases biological activity of both the molecules. Our research group has published many papers on incorporated heterocyclic ring structures, viz; imatinibium dipicrate zepin-11-yl)piperazinium hemifumarate (Ravikumar & Sridhar, 2005), Cinnarizinium fumarate (Kavitha et al., 2013). In view of the importance of the incorporated of heterocyclic ring compounds and derivative of pyrimidyl piperazines, this paper reports the crystal structure of the title salt.
Bond lengths are in normal ranges (Allen et al., 1987).
In the crystal, a single strong short O1B-H1B···O3B hydrogen bond links the anions resulting in chains along the c axis (Table 1 and Fig. 2). The chains are linked via N-H···O hydrogen bonds to form sheets parallel to (100). A weak C8A-H8A···O2B hydrogen bond links the cations and anions forming a three-dimensional structure with alternate layers of cations and anions (Table 1 and Fig. 2). In addition, weak π-π interactions involving inversion related pyrimidine rings are present [Cg-Cg i = 3.820 (9)

Refinement
Atom H1B was freely refined and all of the remaining H atoms were placed in their calculated positions and refined using the riding model approach: N-H = 0.99 Å for NH 2 H atoms, C-H = 0.95 and 0.99Å for CH and CH 2 H atoms, respectively, with U iso (H) = 1.2U eq (N,C).

Figure 1
A view of the molecular structure of the title salt, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

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.