catena-Poly[[[bis(thiocyanato-κN)zinc(II)]-μ-1,2-bis{[2-(2-pyridyl)-1H-imidazol-1-yl]methyl}benzene] 0.28-hydrate]

The title one-dimensional coordination polymer, {[Zn(NCS)2(C24H20N6)2]·0.28H2O}n, was obtained by the reaction of Zn(OAc)2·2H2O, KSCN and 1,2-bis{[2-(2-pyridyl)-1H-imidazol-1-yl]methyl}benzene (hereafter L). The ZnII ion shows a distorted octahedral coordination geometry and is coordinated by two N atoms from two SCN− anions and four N atoms from two organic ligands. The L ligands act as bridging bis-chelating ligands with cis coordination modes at the ZnII ion. One-dimensional coordination polymers are arranged into layers by π–π stacking interactions between the imidazole rings of adjacent chains, with an interplanar distance of 3.46 (1) Å and centroid–centroid distances of 3.8775 (16) Å. One of the thiocyanate ligands is disordered over two positions with an occupancy factor of 0.564 (3) for the major component. The partially occupied water molecule forms an O—H⋯S hydrogen bond with the disordered thiocyanate group.

We greatly acknowledge the financial support of this work by the Department of Education of Jilin Province. [[[bis(thiocyanato-N)

Comment
In recent years, there is an increasing interest in metal-organic frameworks (MOFs) for the versatile architectures and intriguing topologies as well as their wide potential applications (Dybtsev et al. 2004;Evans & Lin, 2002). A universal strategy for the construction of MOFs is dependent primarily on the appropriate choice of inorganic building blocks and different organic ligands. Among them, N-donor organic ligands are important because of their divers coordination modes to metal ions resulting in different structures (Janiak, 2003) and the ability to form of weak interactions to assemble supramolecular structures (Moulton & Zaworotko, 2001). In this case, 1,2-bis{[2-(2-pyridyl)-1H-imidazol-1-yl]methyl}benzene (hereafter L) is selected as organic ligand and reacted with Zn(OAc) 2 .2H 2 O and KSCN to obtain the title compound.
In the title compound, there is one kind of L ligand, Zn II ion and two kinds of SCNanions in the unit cell ( Fig. 1).
Each Zn II ion is coordinated by two nitrogen atoms from two SCNanions and four aromatic N atoms from two different L molecules with normal Zn-N distances (Dai et al. 2002;Luan et al. 2006), showing a distorted octahedral coordination geometry. Each L molecule is acting as a bridging bis-bidentate ligand coordinated to two Zn II ions to form polymeric one-dimensional chain (Fig. 2). Moreover, a two-dimensional supramolecular layer is finally formed by linking these chains through the π-π stacking interactions between imidazole rings from adjacent chains, with the plane to plane distance of 3.46 (1) Å and the centroid-centroid distances of 3.87 (8) Å. (Fig. 3).
Colorless polyhedron crystals were collected in 85% yield.

Refinement
The disordered SCNanion was refined with S and C atoms split over two sites, with the sum of the occupancy factors equal to 1.00. In this anion restraints were imposed on the anion geometry (DFIX instructions of SHELXL-97) and anisotropic displacement parameter of C and S atoms (ISOR instruction). The occupancy factor of the water molecule was initially refined but it was fixed in the final refinement cycles. Positions of H atoms from water molecules were calculated assuming interactions with the anion S atoms and these atoms were refined as riding with O-H = 0.85 Å and U iso =1.5U eq (O). All H atoms bound to C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 and 0.97 Å, and Fig. 1. A displacement ellipsoids view of the title compound with the displacement ellipsoids drawn at the 30% probability level. Symmetry code #2: x, -y+1/2, z-1/2. Fig. 2. View of the one-dimensional chain. Fig. 3. View of the two-dimensional supramolecular structure formed by π-π stacking interactions.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (