catena-Poly[[dichloridozinc(II)]-μ-2,5-di-4-pyridyl-1,3,4-thiadiazole-κ2 N 2:N 5]

The title compound, [ZnCl2(C12H8N4S)]n, was obtained by crystallization of 2,5-di-4-pyridyl-1,3,4-thiadiazole with ZnCl2 in an MeOH/CHCl3 solvent system. The structure contains infinite chains of ZnCl2 units connected by the bifunctional thiadiazole ligands, with ZnII adopting a distorted tetrahedral coordination geometry. The dihedral angle between the two pyridyl rings in each ligand is 34.3 (1)°, and the dihedral angles between the thiadiazole ring and the two pyridyl rings are 18.3 (2) and 16.1 (2)°. The shortest Zn⋯Zn distance within each polymeric chain is 11.862 (3) Å, while the shortest interchain Zn⋯Zn distance is 7.057 (3) Å.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BI2274).

Comment
Much current research activity of supramolecular coordination polymers with novel topologies and structural motifs is driven by their encouraging potential applications in the fields of nonlinear optics, catalysis and separation, magnetism and molecular recognition (Moulton & Zaworotko, 2001, Xiong et al., 2001, Inoue et al., 1996. Therefore, the discovery and rational design of such coordination polymers is an important and very active topic. One useful strategy for the discovery of novel coordination polymers has been the use of various spacer ligands as the building block (Du et al., 2003, Chen et al., 2007. So far, a wide range of infinite frameworks have already been generated with simple 4,4'-bipyridyl-based ligands (Maekawam et al., 2000, Fujita, 1998. As previously reported , Huang et al., 2004, oxadiazole-containing ligands can take versatile bonding modes (it can act as mono-, bi-, tri-and even tetradentate ligand) and the structural geometries of the ligands themselves are also variable. On the other hand, d 10 transition metal-containing complexes often show interesting optical properties. Our interest in the supramolecular coordination polymers lead us to use 2,5-di-4-pyridyl-1,3,4-thiadiazole (L) and ZnCl 2 as precursors to generate the title compound.
Crystallization of L and ZnCl 2 in MeOH/CHCl 3 mixed solvent system at room temperature yield the title compound, [Zn(C 12 H 8 N 4 S)Cl 2 ] n . The crystal structure is composed of 1-D zigzag chains with ZnCl 2 units connected to each other by the N-donor bifunctional ligands. As shown in Fig. 1, the Zn II center adopts a distorted tetrahedral coordination geometry, defined by two N donors from two 2,5-di-4-pyridyl-1,3,4-thiadiazole ligands (L) and terminal chloride ligands. Both Zn-N bond distances are 2.060 (2) Å, and the two Zn-Cl bond distances are 2.1938 (8) and 2.2402 (8) Å, respectively. The greatest angular distortion from tetrahedral geometry is exhibited by the Cl-Zn-Cl angle of 127.44 (3) ° and by the N-Zn-N angle of 103.11 (9) °. All these values compare well to those reported in other [Zn(4,4'-bipy)] compounds (Dong, Ma, Huang, Guo et al., 2003). The two pyridyl ring groups in each ligand are not coplanar, and the dihedral angle between them is 34.3 (1) °. The dihedral angles between the thiadiazole ring and the two pyridyl ring groups in each ligand are 18.3 (2) °a nd 16.1 (2) °. The intrachain Zn···Zn distance is 11.862 (3) Å, while the shortest interchain Zn···Zn distance is 7.057 (3) Å.
In the crystal, the 1-D zigzag chains stack along crystallographic β axis. In the ac plane (Fig. 2), neighboring chains are arranged in opposite directions, and are stacked either in a shoulder-to-shoulder or a staggered fashion.

catena-Poly[[dichloridozinc(II)]-µ-2,5-di-4-pyridyl-1,3,4-thiadiazoleκ 2 N 2 :N 5 ]
Crystal data [ZnCl 2 (C 12  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 Rfactors(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.