catena-Poly[[diaquazinc(II)]-μ-4,4′-(methylenedioxy)dibenzoato]

In the title complex, [Zn(C15H10O6)(H2O)2]n, the ZnII atom is located on a twofold rotation axis and exhibits a distorted tetrahedral coordination environment defined by two O atoms from two 4,4′-(methylenedioxy)dibenzoate ligands and two O atoms from two coordinated water molecules. In the crystal structure, molecules are linked into a three-dimensional framework by O—H⋯O hydrogen bonds and C—H⋯π interactions.

In the title complex, [Zn(C 15 H 10 O 6 )(H 2 O) 2 ] n , the Zn II atom is located on a twofold rotation axis and exhibits a distorted tetrahedral coordination environment defined by two O atoms from two 4,4 0 -(methylenedioxy)dibenzoate ligands and two O atoms from two coordinated water molecules. In the crystal structure, molecules are linked into a three-dimensional framework by O-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions.

Comment
Recently, the area of metal-organic framework materials has become one of the intense research activity for their fascinating structural diversities and potential applications in catalysis, nonlinear optics and molecular sensing. As an important family of multidentate O-donor ligands, organic aromatic polycarboxylate ligands have been extensively employed in the preparation of metal-organic complexes because of their potential properties and intriguing structural topologies (Han et al., 2009;Li et al., 2007;Chen et al., 2002). Herein, we report the structure of the title complex with bis(4-benzoateoxyl)methane and zinc, [Zn(C 15 H 10 O 6 )(H 2 O) 2 ] (I).
Single-crystal X-ray diffraction analyses revealed Zn(II) is tetra-coordinated and exhibits tetrahedral coordination environment supplied by two bis(4-benzoateoxyl)methane O atoms and two water molecules (Fig. 1). The Zn-O bond lengthes are in the normal range (Table 1). The bis(4-benzoateoxyl)methane ligand adopts bidentate coordinated modes and bond with two zinc ions to form a chain. Adjacent chains are linked by O-H···O hydrogen bonds and C-H···π interactions into a three-dimensional supramolecular network structure (Fig. 2, Table 2).
After cooling slowly to room temperature at a rate of 10 K h -1 , colourless crystals of (I) were obtained.

Refinement
C-bound H atoms were treated as riding, with C-H = 0.93 and 0.97Å and U iso (H) = 1.2 times U eq (C). O-bound H atoms were located in a difference Fourier map and refined as riding in their as-found relative positions; U iso (H) = 1.5U eq (O). Fig. 1. View of the local coordination of Zn(II) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.  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.