catena-Poly[[aqua[1,4-bis(1H-imidazol-4-yl)benzene]cadmium]-μ3-5-methylisophthalato]

In the title coordination polymer, [Cd(C9H6O4)(C12H10N4)(H2O)]n, the CdII atom has a NO6 donor set and is coordinated by five carboxylate O atoms from three different 5-methyl-1,3-phenylenediacetate (pda2−) anions, one O atom from a water molecule and one N atom from a 1,4-bis(1H-imidazol-4-yl)benzene (L) ligand, displaying a highly distorted pentagonal–bipyramidal geometry. Each pda2− anion acts as a μ3-bridge, linking CdII atoms to form one-dimensional slabs extending parallel to [010]. In the crystal, adjacent molecules are linked through N—H⋯N and N—H⋯O hydrogen bonds into a three-dimensional network.

In the title coordination polymer, [Cd(C 9 H 6 O 4 )(C 12 H 10 N 4 )-(H 2 O)] n , the Cd II atom has a NO 6 donor set and is coordinated by five carboxylate O atoms from three different 5methyl-1,3-phenylenediacetate (pda 2À ) anions, one O atom from a water molecule and one N atom from a 1,4-bis(1Himidazol-4-yl)benzene (L) ligand, displaying a highly distorted pentagonal-bipyramidal geometry. Each pda 2À anion acts as a 3 -bridge, linking Cd II atoms to form one-dimensional slabs extending parallel to [010]. In the crystal, adjacent molecules are linked through N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds into a three-dimensional network.

Comment
The rational design and synthesis of metal-organic frameworks (MOFs) has attracted considerable attention, which is stimulated by their intriguing aesthetic structures and topological features as well as their potential applications as materials (Bradshaw et al., 2005;Ockwig et al., 2005). The choice of suitable ligands is a key factor that greatly affects the structure and stabilization of the coordination architecture (Choi & Jeon 2003). For a more tunable ligand design mixed polycarboxylate and N-containing compounds (Liu et al., 2007;Chen et al., 2006) are favourable. Therefore we have focused on constructing complexes based on the organic ligand 1,4-di(1H-imidazol-4-yl)benzene (L) and polycarboxylate anions (Chen et al., 2010;2011). As an extension of our work, we report the synthesis and structure of a new Cd II complex (I), which was obtained by solvothermal reaction of CdI 2 with L and 5-methylisophthalic acid (H 2 pda).
The asymmetric unit of (I) consists of one Cd II atom, one L ligaqnd, one pda 2anion and one coordinated water molecule.
Each Cd II atom has a NO 6 donor set and is coordinated by five carboxylate oxygen atoms from three different pda 2anions, one water oxygen atom and one nitrogen atom from L, displaying a highly distorted pentagonal-bipyramidal geometry (Fig.   1). The pda 2ligand acts as a µ 3 -bridge with two monodentate carboxylate groups to form one-dimensional slabs parellel to [010] (Fig. 2). In the crystal, adjacent molecules are linked through N-H···N and N-H···O hydrogen bonding interactions into a three-dimensional network (Fig. 3).

Experimental
All reagents and solvents were used as obtained commercially without further purification. A mixture containing CdI 2 (36.6 mg, 0.1 mmol), L (21.0 mg, 0.1 mmol), H 2 pda (18.0 mg, 0.1 mmol), DMF (N:N'-dimethylformamide, 1 ml), 10 ml H 2 O was sealed in a 16 ml Teflon-lined stainless steel container and heated at 453 K for 72 h. After cooling to room temperature within 12 h, colorless crystals of (I) suitable for X-ray diffraction analysis were obtained in 48% Yield.

Refinement
H atoms bonded to C atoms were placed geometrically and treated as riding, with C-H distances 0.93 Å and 0.96 Å for aryl and methyl type H-atoms, respectively with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (C methyl ). The amide H atoms were located from difference maps and refined with the N-H distances restrained to 0.86 Å and U iso (H) = 1.2U eq (N). The hydrogen atoms of the coordinated water molecule could not be located and thus were not included in the refinement.