Poly[[diaqua(μ4-l-tartrato)(μ2-l-tartrato)dizinc(II)] tetrahydrate]

In the title compound, {[Zn(C4H4O6)(H2O)]·2H2O}n, the l-tartrate ligands adopt μ4- and μ2-coordination modes. The ZnII atom adopts an octahedral geometry and is chelated by two kinds of l-tartrate ligands through the hydroxy and carboxylate groups and coordinated by one unchelating carboxylate O atom and one water molecule. In the crystal, the l-tartrate ligands link the ZnII atoms, forming a two-dimensional coordination layer; these layers are futher linked into a three-dimensional supramolecular network by O—H⋯O hydrogen bonds between the two-dimensional coordination layers and the uncoordinated water molecules. The latter are equally disordered over two positions.

In the title compound, {[Zn(C 4 H 4 O 6 )(H 2 O)]Á2H 2 O} n , the ltartrate ligands adopt 4 -and 2 -coordination modes. The Zn II atom adopts an octahedral geometry and is chelated by two kinds of l-tartrate ligands through the hydroxy and carboxylate groups and coordinated by one unchelating carboxylate O atom and one water molecule. In the crystal, the l-tartrate ligands link the Zn II atoms, forming a twodimensional coordination layer; these layers are futher linked into a three-dimensional supramolecular network by O-HÁ Á ÁO hydrogen bonds between the two-dimensional coordination layers and the uncoordinated water molecules. The latter are equally disordered over two positions.

D-HÁ
Data collection: SMART (Sheldrick, 2008); cell refinement: SAINT (Sheldrick, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97. Comment Chiral inorganic-organic materials have received much attention, not only because of their numerous potential applications in nonlinear optics, enantioselective catalysis and medicine, but also owing to their intriguing variety of architectures and topologies (Ma et al., 2007;Kitagawa et al., 2004;Lee et al., 2002). L-tartaric acid, a simple and inexpensive chiral ligand source, was often used to construct novel chiral multifunctional materials (Liu et al., 2008;Gelbrich et al., 2006). Firstly, tartaric acid is flexible dicarboxylate ligands with two hydroxyl groups, and can offer more coordination sites and allow the formation of five-or six-membered ring, which can stabilize the solid network. Secondly, the deprotonated carboxylate group possesses polarizable system, it can transfer electrons easily. So, tartrate ligand is a good candidate of constructing chiral magnetic and chiral optical materials. In this paper, we reported the structure of the title compound, which is constructed by the chiral L-tartrate ligand.
X-ray single crystal diffraction studies reveal that the crystallographic unique unit of (I) is composed of one Zn II ion, two halves of L-tartrate ligand, one coordination water and two disordered lattice water molecules with occupancies both in the 0.5:0.5 ratio. As shown in Fig. 1, two kinds of L-tart ligands chelate two Zn centers through the hydroxyl and carboxylate groups in cis confirmation to form [Zn 2 (L-tart) 2 ] dimmer, which is similar to the reported tartrate salts (Coronado et al., 2006). And, the octahedral geometry of Zn II is completed by one unchelating carboxylate oxygen atom and one water molecule. For compound (I), L-tartrate ligands adopt µ 4 -and µ 2 -two coordination modes, which link the [Zn 2 (L-tart) 2 ] dimmers to form two-dimensional coordination layer. The coordination and lattice water molecules hydrogen bond to the hydroxy and carboxylate groups, so the two-dimensional coordination layers are further linked together to form three-dimensional supramolecular network (shown in Fig. 2). The parameters of hydrogen bonds are listed in Table 1.

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 > 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.