Bis(2,2′-bipyridine-κ2 N,N′)(3-methylbenzoato-κ2 O,O′)zinc 3-methylbenzoate–3-methylbenzoic acid–water (1/1/2)

The title compound, [Zn(C8H7O2)(C10H8N2)2](C8H7O2)·C8H8O2·2H2O, is comprised of a Zn2+ cation, two 2,2′-bipydine (bipy) ligands and one 3-methylbenzoate anion (L −) together with one uncoordinating L − anion, one uncoordinating HL molecule and two lattice water molecules. The ZnII atom is coordinated by four N atoms of two bipy ligands and two O atoms from one L − ligand in a distorted octahedral geometry. Pairs of centrosymmetrically related complex molecules form dimers via slipped π-stacking interactions between bipy ligands with an interplanar distance of 3.470 (4) Å. The dimers are linked into supramolecular chains along [111], via C—H⋯O hydrogen bonds. The uncoordinated L − anions, HL molecules and water molecules are connected with each other via O—H⋯O hydrogen bonds, forming chains between the metal complex chains and binding them together via C—H⋯O contacts. The resulting layers parallel to (010) are further assembled into a three-dimensional supramolecular architecture through additional C—H⋯O interactions.


Related literature
For general background to complexes with intriguing topological structures, see: Chen et al. (2010) and for complexes with potential applications in gas storage and separation, magnetism, luminescence and catalysis see: Bettencourt-Dias & Viswanathan (2006); Liu et al. (2006); Xu et al. (2010Xu et al. ( , 2011.
Sincere thanks are extended to the K. C. Wong Magna Fund in Ningbo University.

Qiu-qi Ye, Jin-li Qi and Jian-li Lin Comment
In recent years, the design and synthesis of metal-organic frameworks (MOFs) have attracted considerable attention due to their intriguing topological structures (Chen et al., 2010) and potential applications in gas storage and separation, magnetism, luminescence, and catalysis (Bettencourt-Dias et al., 2006;Liu et al., 2006;Xu et al., 2010;Xu et al., 2011).
Two centrosymmetrically-related metal complexes molecules have bipy rings which are parallel with an interplanar distance of 3.470 (4) Å suggesting a slipped π···π stacking interaction. This together with weak, pairwise C17-H17A···O1 hydrogen bonds (Table 1) (Table 1) and π···π stacking interactions with a distance of 3.455 (4) Å between the bipy rings which are not engaged in π···π stacking within the dimeric units (Fig.2). The uncoordinated Lanions, HL molecules and water molecules connect with each other via O-H···O hydrogen bonds to form chains between the metal complex chains and connect with the latter via C8-H18A···O8 contacts ( Table 1). The resulting layers are further assembled into a three-dimensional supramolecular architecture through additional C-H···O interactions. solution was allowed to evaporate at room temperature for several days to give colourless block-shaped crystals.

Refinement
H atoms bonded to C were placed in calculated positions and were refined using a riding model, with U iso (H) = 1.2 U eq (C). H atoms attached to O were placed in locations indicated by a difference Fourier synthesis and were refined using a riding model with U iso (H) values set at 1.2 Ueq(O).

Computing details
Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).  One-dimensional supramolecular chain along [111] formed by C7-H7A···O2 hydrogen bonds and π···π stacking interactions.  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 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.