catena-Poly[[[tetraaquazinc(II)]-μ-4,4′-bipyridine-κ2 N:N′] benzene-1,4-dicarboxylate]

In the title compound, {[Zn(C10H8N2)(H2O)4](C8H4O4)}n, the ZnII atoms, lying on a twofold rotation axis, are bridged by 4,4′-bipyridine ligands, resulting in a linear chain along the b axis. In the chain, the ZnII atom adopts a slightly distorted octahedral coordination geometry involving four water molecules at the equatorial positions. The noncoordinated benzene-1,4-dicarboxylate anion, which is also located on a twofold rotation axis, bridges adjacent chains through O—H⋯O hydrogen bonds, forming a three-dimensional supramolecular network.

In the title compound, {[Zn(C 10 H 8 N 2 )(H 2 O) 4 ](C 8 H 4 O 4 )} n , the Zn II atoms, lying on a twofold rotation axis, are bridged by 4,4 0 -bipyridine ligands, resulting in a linear chain along the b axis. In the chain, the Zn II atom adopts a slightly distorted octahedral coordination geometry involving four water molecules at the equatorial positions. The noncoordinated benzene-1,4-dicarboxylate anion, which is also located on a twofold rotation axis, bridges adjacent chains through O-HÁ Á ÁO hydrogen bonds, forming a three-dimensional supramolecular network.
Compound, (I), as shown in Fig. 1, consists of one-dimensional [Zn(C 10 H 8 N 2 )(H 2 O) 4 ] n cation chains and benzene-1,4-dicarboxylate anions. The Zn(II) atoms are in a slightly distorted octahedral geometry, where two N atoms from two 4,4′bipyridine ligands occupy the axial positions, and the equatorial positions are completed by four water molecules. The compound crystallizes in a centrosymmetric space group, which defines twofold axes along both the one-dimensional chains and the benzene-1,4-dicarboxylate anions.

S2. Experimental
Compound (I) was solvothermally prepared from a reaction mixture of Zn(BF 4 ) 2 (0.2 mmol), 4,4′-bipyridine (0.1 mmol), benzene-1,4-dicarboxylic acid (0.1 mmol), methanol (3 ml) and distilled water (8 ml) in a molar ratio of 2:1:740:4444; the pH value was adjusted to 4.8 with trimethylamine and acetic acid. The mixture was stirred for 20 min at room temperature and then sealed in a Teflon-lined stainless steel autoclave with a 23 ml capacity at 423 K for 72 h. After cooling to room temperature, colourless block-shaped crystals were obtained; these were washed with deionized water, filtered, and dried in air (yield 48% based on Zn).

S3. Refinement
C-bound H atoms were placed geometrically (C-H = 0.93 Å) and were refined using a riding model, with U iso (H) = 1.2U eq (C). H atoms on the water molecules were located in a difference Fourier map and the positions were fixed, with The structure of (I), showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
View of the three-dimensional supramolecular structure in (I). Dashed lines indicate hydrogen bonds.

catena-Poly[[tetraaquazinc(II)]-µ-4,4′-bipyridine-κ 2 N:N′] benzene-1,4-dicarboxylate]
Crystal data [Zn(C 10  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.64 e Å −3 Δρ min = −0.27 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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