Poly[[[aqua(2,2′-bipyridine-κ2 N,N′)zinc(II)]-μ-2-nitroterephthalato-κ2 O 1:O 4] monohydrate]

In the title compound, {[Zn(C8H3NO6)(C10H8N2)(H2O)]·H2O}n, the ZnII ion is square-pyramidally coordinated, and bridged by 2-nitro-terephthalate ligands, forming a chain running along [10]. Intramolecular hydrogen bonds are formed between the coordinated water molecules and the nitro O atoms. Adjacent chains are linked by hydrogen bonds between the coordinated water molecules and the O atoms of the monodentate carboxyl groups.

In the title compound, {[Zn(C 8 H 3 NO 6 )(C 10 H 8 N 2 )(H 2 O)]Á-H 2 O} n , the Zn II ion is square-pyramidally coordinated, and bridged by 2-nitro-terephthalate ligands, forming a chain running along [110]. Intramolecular hydrogen bonds are formed between the coordinated water molecules and the nitro O atoms. Adjacent chains are linked by hydrogen bonds between the coordinated water molecules and the O atoms of the monodentate carboxyl groups.
We are grateful for financial support by the National Natural Science Foundation of China (grant No. 20471049) and Xiamen University.
In the structure of I, the asymmetric unit contains one Zn II ion, one ntp ligand, one coordinated water molecule, one 2,2'bpy and one solvent water molecule. (Fig. 1, Table 1) The Zn II ion is in a distorted square pyramidal geometry, coordinated by two carboxylate oxygen atoms from two ntp briding ligands, one oxygen atom from water molecule and two nitrogen atoms from 2,2'-bpy. In ntp, the carboxyl in the ortho position of nitro substituent adopts monodentate coordination mode, and the dihedral angle between it and the benzene ring is 45.96 °; the other carboxyl adopts semi-chelating mode, the dihedral angle is 11.35 °. In the semi-chelating mode, one of the coordination bond is very long and weak and is almost neglectable.
(Zn1-O3 i = 2.859 Å, i x -1, y + 1, z) The Zn II ion is bridged by ntp ligands to form a one dimensional chain running along [1 -1 0] direction (Fig. 2). Intramolecular hydrogen bonds are formed between the coordinated water molecules and the nitro oxygen atoms. Adjacent chains also form intermolecular hydrogen bonds between the coordinated water molecules and the oxygen atoms of the monodentate carboxyl groups (Table 2).

Experimental
The suspension of 2-nitro-terephthalic acid (0.042 g, 0.20 mmol) and 2,2'-bipyridine (0.033 g, 0.20 mmol) in H 2 O (10 mL) was vigorously stirred, aqueous solution of sodium hydroxide (2 mol/L) was slowly added until the pH value was adjusted to 7, and then ZnCl 2 (0.027 g, 0.20 mmol) was added. The solution was placed in a 20 mL Teflon-lined vessel, heated to 453 K at the rate of 0.2 K/min, and kept at 453 K for 3 days, and then slowly cooled down to room temperature at the rate of 0.1 K/min. Yellow block crystals (0.035 g, yield 38%) were separated by filtration, washed with deionized water and dried in air. Elemental Analysis: C 18 H 15 N 3 O 8 Zn, found (calc.) C 47.23 (46.32), H 3.30 (3.24), N 9.18 (9.00).

Refinement
The position of the water H atom were refined with O-H distance restrained to 0.85 Å, with their temperature factors set to 1.2 times those of the parent atoms. The aromatic H atoms were generated geometrically (C-H 0.93 Å) and were allowed to ride on their parent atoms in the riding model approximations, with their temperature factors set to 1.2 times those of the parent atoms.  Poly [[[aqua(2,2'-bipyridine-κ 2 N,N')

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