Diaquabis{3-[4-(1H-imidazol-1-yl)phenyl]-5-(pyridin-2-yl-κN)-1H-1,2,4-triazol-1-ido-κN 1}zinc

The centrosymmetric molecule of the title compound, [Zn(C16H11N6)2(H2O)2], contains one Zn2+ ion located on a center of symmetry, two 3-[4-(1H-imidazol-1-yl)phenyl]-5-(pyridin-2-yl)-1H-1,2,4-triazol-1-ide (Ippyt) ligands and two coordinating water molecules. The ZnII ion is six-coordinated in a distorted octahedral coordination geometry by four N atoms from two Ippyt ligands and by two O atoms from two water molecules. Adjacent units are interconnected though O—H⋯N hydrogen bonds, forming a three-dimensional network.


Experimental
Crystal data [Zn(C 16 H 11 N 6 ) 2 (H 2 O) 2 ] M r = 676.04 Monoclinic, P2 1 =c a = 12.6481 (9) Å b = 11.6659 (6) Å c = 10.4922 (7) Table 1 Hydrogen-bond geometry (Å , ). The rational design and syntheses of metal-organic frameworks have been of increasing interest in the crystal engineering of coordination polymers owing to their ability to provide diverse assemblies with fascinating topological structures and material properties ( Han et al., 2005;Xue et al.,2009). The centrosymmetric unit of the title compound contains one Zn 2+ ion, two Ippyt ligands and two coordination water molecules. For a similar structure, see: Braga et al. (2005); Lin et al. (2010);Faulmann et al. (1990). Every Zn II ion is six-coordinated in a distorted octahedral coordination geometry by four N atoms from two Ippyt ligands and by two O atoms from two coordination water molecules ( Fig. 1). There are two kinds of hydrogen bonding interactions which are between the coordinated waters and the triazolyl nitrogen atoms, and between the coordinated waters and the imidazolyl nitrogen atoms, respectively. However, the construct units are connected by the hydrogen bonding interactions between oxygen/ imidazolyl nitrogen atoms and imidazolyl nitrogen/ oxygen atoms from adjacent units respectively. Thus, infinite one-dimensional ring-shaped chains are formed. And then N3 and N3′ are further involved in forming another hydrogen bonding interactions with other neighbouring water oxygen atoms and thus connect the 1D supramolecular chains together to form the two-dimensional supramolecular architecture in the a,c plane. And finally the structures are interlinked alternately by different hydrogen bonding interactions and finally result in the three-dimensional supramolecular network architectures. (Fig.2).

Experimental
A mixture of Zn(NO 3 ) 2 .6H 2 O (0.02 mmol), Ippyt (0.02 mmol), H2O (8 ml) was sealed in 25ml Teflon-lined stainless steel reactor, which was heated to 413 K for 5d and was subsequently cooled slowly to room temperature. Colourless blockshaped crystals were collected in 47% yield based on Zn.

Refinement
All H atoms were positioned geometrically (C-H = 0.93Åand O-H = 0.82 Å) and allowed to ride on their parent atoms, with U iso (H) values equal to 1.2U eq (C) or 1.5U eq (O).

Figure 2
The 3D supermolecule network of the title compound. Dashed lines denote hydrogen bonds.

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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.