Crystal structure of bis{μ-4,4′-[1,3-phenylenebis(oxy)]dibenzoato-κ4 O,O′:O′′,O′′′}bis[(1,10-phenanthroline-κ2 N,N′)zinc(II)] dihydrate

Two 4,4′-[1,3-phenylenebis(oxy)]dibenzoate anions bridge two 1,10-phenanthroline-chelated ZnII cations about a center of inversion to generate the dinuclear title compound, [Zn2(C20H12O6)2(C12H8N2)2]·2H2O. The geometry about the ZnII atom is a distorted octahedron. In the crystal, the molecules are connected by classical O—H⋯O hydrogen bonds, weak C—H⋯O hydrogen bonds and C—H⋯π interactions, forming a three dimensional network. π–π stacking is also observed between aromatic rings of adjacent molecules, centroid–centroid distances are 3.753 (2), 3.5429 (16) and 3.5695 (17) Å.


S1. Structural commentary
The rational design and construction of coordination polymers based upon assembly of metal ions and multifunctional organic ligands has drawn widespread attentions because of their potential applications as functional materials and intriguing varieties of architectures and topologies (Hökelek & Necefouglu, 1996). The structures of coordination polymers are usually influenced by a multitude of factors such as geometrical and electronic properties of the metal ions employed, coordination abilities of the ligands, the ligand-to-metal ratio, and the use of different solvents (Necefoglu et al., 2002). In this paper, we selected 4,4′-(1,3-phenylenebis(oxy))dibenzoic acid as a linker and 1,10-phenanthroline as a secondary ligand, resulting in the title complex.
In the title compound,[Zn 2 (C 20 H 12 O 6 ) 2 (C 12 H 8 N 2 ) 2 ] . 2H 2 O, the Zn II atom is surrounded by two N atoms from one 1,10phenanthroline and four O atoms from two 4,4′-(1,3-phenylenebis(oxy))dibenzoate ligands (Fig. 1). The geometry of the ZnII atom is a distorted octahedron and the neighboring two Zn II atoms are bridged by two 4,4′-(1,3-phenylenebis(oxy))dibenzoate dianions. Adjacent molecules are connected to the lattice water molecule by hydrogen bonds to form a linear ribbon running along the b-axis of the triclinic unit cell (Fig. 2). Adjacent dimers are further linked through intermolecular O-H···O hydrogen bonds, leading to a three-dimensional supramolecular structure (Fig. 2).

S3. Refinement
All C-H H atoms were positioned with idealized geometry and refined isotropic with U iso (H) = 1.2 U eq (C) using a riding

Figure 2
Crystal structure of the title compound with view along the a-axis.

Bis{µ-4,4′-[1,3-phenylenebis(oxy)]dibenzoato-κ 4 O,O′:O′′,O′′′}bis[(1,10-phenanthroline-κ 2 N,N′)zinc(II)]
dihydrate 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.