catena-Poly[[(dichloridozinc)-μ-4,4′-bis(1H-imidazol-1-yl)biphenyl-κ2 N 3:N 3′] 0.25-hydrate]

In the title one-dimensional coordination polymer, {[ZnCl2(C18H14N4)]·0.25H2O}n, the ZnII atom is coordinated by two chloride ions and two 4,4′-bis(1H-imidazol-1-yl)biphenyl ligands, generating a distorted tetrahedral ZnCl2N2 geometry. The dihedral angle between the benzene rings of the ligand is 51.0 (1)° and the dihedral angles between the benzene rings and their attached imidazole rings are 18.7 (2) and 45.9 (1)°. The bridging ligand leads to [10-1] polymeric chains in the crystal and the disordered water molecule (occupancy 0.25) forms O—H⋯Cl hydrogen bonds.

In the title one-dimensional coordination polymer, {[ZnCl 2 -(C 18 H 14 N 4 )]Á0.25H 2 O} n , the Zn II atom is coordinated by two chloride ions and two 4,4 0 -bis(1H-imidazol-1-yl)biphenyl ligands, generating a distorted tetrahedral ZnCl 2 N 2 geometry. The dihedral angle between the benzene rings of the ligand is 51.0 (1) and the dihedral angles between the benzene rings and their attached imidazole rings are 18.7 (2) and 45.9 (1) . The bridging ligand leads to [101] polymeric chains in the crystal and the disordered water molecule (occupancy 0.25) forms O-HÁ Á ÁCl hydrogen bonds.

Related literature
For background to coordination polymers containing imidazole-derived ligands, see: Li et al. (2010Li et al. ( , 2011.

Experimental
Crystal data [ZnCl 2 (C 18   In recent years, imidazole has been well used in crystal engineering, and a large number of imidazole-containing flexible ligands have been extensively studied. However, to our knowledge, the research on imidazole ligands bearing rigid spacers is less developed (Li et al., 2010;Li et al., 2011).
Single-crystal X-ray diffraction analysis reveals that the title compound (I) crystallizes in the monoclinic space group P21/n. For the title compound, the geometry of the Zn II ion is bound by two imidazole rings of individual L ligands, and two chlorine anions, which illustrates a slightly distorted tetrahedral coordination environment (Fig 1). Notably, as shown in Fig. 2, the four-coordinate Zn II center is bridged by the ligand L to form an infinite one-dimensional architecture.

Experimental
A mixture of CH 3 OH and H 2 O (1:1, 8 ml), as a buffer layer, was carefully layered over a solution of ZnCl 2 (0.02 mmol) in H 2 O (6 ml). Then a solution of 4,4′-bis(1H-imidazol-1-yl)phenyl (L, 0.06 mmol) in CH 3 OH (6 ml) was layered over the buffer layer, and the resultant reaction was left to stand at room temperature. After ca three weeks, colorless block single crystals appeared at the boundary. Yield: ~25% (based on L).

Refinement
The dispalcement parameters for the water O atom were very large at full occupancy. When refined, its fractional occupancy converged to close to 0.25 and was then set at this value. C-bound H atoms were positioned geometrically and refined in the riding-model approximation, with C-H = 0.93Å and U iso (H) = 1.2U eq (C).  The molecular structure of (I). Displacement ellipsoids are drawn at the 30% probability level.  The crystal packing for (I).

catena-Poly[[(dichloridozinc)-µ-4,4′-bis(1H-imidazol-1-yl)biphenyl-κ 2 N 3 :N 3′ ] 0.25-hydrate]
Crystal data 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 > σ(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. (