catena-Poly[[[bis(methylamine)zinc(II)]-μ-4,4′-oxydibenzoato] N,N-dimethylacetamide solvate]

In the title zinc(II) coordination polymer, {[Zn(C14H8O5)(CH5N)2]·C4H9NO}n, each Zn(II) cation is tetrahedrally coordinated by two carboxylato O atoms of two oba anions (H2oba is 4,4′-oxydibenzoic acid), and two N atoms from two methylamine molecules. Each oba anion bridges two Zn(II) cations through the two carboxylate groups in a monodentate fashion, forming one-dimensional polymeric chains. These chains are linked via N–H⋯O hydrogen bonds, forming a two-dimensional supramolecular network.

In the title zinc(II) coordination polymer, {[Zn(C 14 H 8 O 5 )-(CH 5 N) 2 ]ÁC 4 H 9 NO} n , each Zn(II) cation is tetrahedrally coordinated by two carboxylato O atoms of two oba anions (H 2 oba is 4,4 0 -oxydibenzoic acid), and two N atoms from two methylamine molecules. Each oba anion bridges two Zn(II) cations through the two carboxylate groups in a monodentate fashion, forming one-dimensional polymeric chains. These chains are linked via N-HÁ Á ÁO hydrogen bonds, forming a two-dimensional supramolecular network.

S1. Comment
Recently, great interest has been focused on the design and synthesis of coordination polymers because of their intriguing network topologies and promising applications (Yaghi et al., 1998). It is well known that the selection of appropriate organic ligands is crucial to the design and synthesis of the supramolecular architectures. In preparing target metal complexes, carboxylate and organic amine ligands have been frequently employed (Luo et al., 2003). More and more interest has focused on long flexible ligands recently, and how to avoid, or make use of, their interpenetration to construct novel coordination polymers is an interesting challenge. 4,4′-oxybis(benzoic acid) (H 2 oba) ligand, in which two benzene moieties are linked together by a µ 2 -O bridge, is the typical example of flexible ligand and may offer more possibilities in geometry configuration and coordination modes towards the metal ions. As far as we know, several coordination polymers based on 4,4′-oxybis(benzoic acid) have been obtained (Kondo et al., 2004;Sun et al., 2005). We present here the solvothermal synthesis and crystal structure of title coordination polymer, [Zn(C 14 H 8 O 5 )(CNH 5 ) 2 . (C 4 NOH 9 )] n , (I).
The asymmetric unit of (I) consists of one crystallogaphically independent Zn(II) cation, one oba ligand, two methylamine and one dimethylacetamide molecule. Fig.1 shows the molecular structure of (I) with the atom-labelling scheme.
The Zn(II) cation has a slightly distorted tetrahedral coordination geometry and formed by two carboxy oxygen atoms  (Table 2). In addition, dimethylacetamide molecules located in the crystal lattice with N-H ··· O hydrogen bonding interactions involving the oxygen atoms of dimethylacetamide molecules and N-H groups of methylamine molecules (Table 2). Finally, the chains are linked together by hydrogen bonds to form two-dimensional supramolecular network (Fig. 2).

S3. Refinement
The H atoms were placed in geometrical calculated positions, with C-H distances of 0.93-0.96 Å and N-H distances of 0.90 Å. A common displacement parameter was refined for all H atoms.

Figure 1
A perspective view of molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are represented as spheres of arbitrary radii. [symmetry code: (A) x + 1/2,y -1/2,z.].

Figure 2
A packing diagram of (I). The dashed lines indicate the hydrogen bonds.

catena-Poly[[[bis(methylamine)zinc(II)]-µ-4,4′-oxydibenzoato] N,N-dimethylacetamide]
Crystal data 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.