catena-Poly[[[bis(1H-imidazole-κN 3)zinc(II)]-μ2-imidazol-1-ido-κ2 N:N′] nitrate]

The title compound, {[Zn(C3H3N2)(C3H4N2)2]NO3}n, is a one-dimensional coordination polymer along [01-1] with the ZnII atom coordinating to four imidazole/imidazolide rings. The ZnII atom has a regular tetrahedral geometry with the planes of the two monodentate imidazole rings inclined to one another by 87.94 (17)°, while the planes of the bridging imidazolide rings are inclined to one another by 39.06 (17)°. In the crystal, the chains are linked via bifurcated N—H⋯(O,O) hydrogen bonds, forming sheets parallel to (001). These two-dimensional networks are linked via C—H⋯O hydrogen bonds and a C—H⋯π interaction, forming a three-dimensional structure.

The title compound, {[Zn(C 3 H 3 N 2 )(C 3 H 4 N 2 ) 2 ]NO 3 } n , is a onedimensional coordination polymer along [011] with the Zn II atom coordinating to four imidazole/imidazolide rings. The Zn II atom has a regular tetrahedral geometry with the planes of the two monodentate imidazole rings inclined to one another by 87.94 (17) , while the planes of the bridging imidazolide rings are inclined to one another by 39.06 (17) . In the crystal, the chains are linked via bifurcated N-HÁ Á Á(O,O) hydrogen bonds, forming sheets parallel to (001). These twodimensional networks are linked via C-HÁ Á ÁO hydrogen bonds and a C-HÁ Á Á interaction, forming a three-dimensional structure.

Related literature
For imidazole systems in biological systems, see: Brooks & Davidson, (1960). For the crystal structure of a similar compound, see: Fu et al. (2007). For the synthesis of the title compound, see: Anbalagan & Lydia (2011). For standard bond lengths, see: Allen et al. (1987).

S1. Comment
Imidazoles are of considerable interest as ligands in many biological systems as they provide potential binding sites for metal ions (Brooks & Davidson, 1960). Against this background and to ascertain the molecular structure and conformation of the title compound, the crystal structure determination has been carried out.
The molecular structure of the title compound is shown in Fig. 1. Atom Zn1 has a regular tetrahedral geometry and the bond lengths (Allen et al., 1987) and angles are normal. It is a one-dimensional zigzag polymer with atom Zn1 coordinating to four imidazole units. This structure is similar to that observed for the compound catena-(bis(µ2- [Fu et al., 2007]. Two of the imidazole units are related by a two-fold screw axis and bridge the zinc atoms. The Zn-N bond distances vary from 1.9871 (18) In the crystal, the chains are linked via bifurcated N-H···O/O hydrogen bonds forming sheets parallel to (001); (Table 1 and Fig. 2). These two-dimensional networks are linked via C-H···O hydrogen bonds and a C-H···π interaction forming a three-dimensional structure.

S2. Experimental
The title compound was synthesized following a published procedure (Anbalagan & Lydia, 2011

S3. Refinement
NH H atoms were located in a difference Fourier map and refined with distance restraints: N-H = 0.88 (2) Å with U iso (H) = 1.2U eq (N). The C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms: C-H = 0.93

Figure 2
A view along the b-axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed bonds (see Table 1 for details; H atoms not involved in these interactions have been omitted for clarity).