The one-dimensional polymer poly[[aqua(2,2′-bipyridine)cadmium(II)]-μ-trans-stilbene-4,4′-dicarboxylato]

In the title polymer, [Cd(C16H10O4)(C10H8N2)(H2O)]n, the CdII ion is in a strongly distorted octahedral geometry, being coordinated by two N atoms from a 2,2′-bipyridine ligand, three carboxylate O atoms from two symmetry-related trans-stilbene-4,4′-dicarboxylate dianions and one water molecule. The stilbene ligand lies on an inversion centre at the midpoint of the central C=C bond. This feature generates the polymeric structure: adjacent CdII ions are bridged by trans-stilbene-4,4′-dicarboxylate dianions, giving rise to a one-dimensional structure. The coordinated water molecule is involved in interchain O—H⋯O hydrogen bonds.

In the title polymer, [Cd(C 16 H 10 O 4 )(C 10 H 8 N 2 )(H 2 O)] n , the Cd II ion is in a strongly distorted octahedral geometry, being coordinated by two N atoms from a 2,2 0 -bipyridine ligand, three carboxylate O atoms from two symmetry-related transstilbene-4,4 0 -dicarboxylate dianions and one water molecule. The stilbene ligand lies on an inversion centre at the midpoint of the central C C bond. This feature generates the polymeric structure: adjacent Cd II ions are bridged by transstilbene-4,4 0 -dicarboxylate dianions, giving rise to a onedimensional structure. The coordinated water molecule is involved in interchain O-HÁ Á ÁO hydrogen bonds.

S1. Comment
We are interested in the solid-state coordination chemistry of trans-stilbene-4,4′-dicarboxylic acid, combined with specific transition metal ions, to fabricate versatile coordination polymers. In our previous work, a one-dimensional Ni IIorganic framework had been reported (Wang et al., 2006). In order to further explore the behavior of trans-stilbene-4,4′dicarboxylic acid as ligand, a new one-dimensional Cd II complex has been obtained and characterized.
The molecular structure of the title compound is illustrated in Fig. 1. The Cd II ion is in a strongly distorted octahedral geometry and is coordinated by two N atoms of a 2,2′-bipyridine ligand, three carboxyl O atoms of two symmetry-related trans-stilbene-4,4′-dicarboxylato dianions, which adopted two different coordination modes, and one water molecule.
One of the two carboxylic ligands is found in the bis-monodentate mode, and the other in the chelating bis-bidentate mode, linking the adjacent Cd II ions into a zigzag chain structure. In addition, the chains are interconnected through intermolecular hydrogen bonds involving water molecules, and π-π interactions involving 2,2′-bipyridine ligands, [centroid-to-centroid separation: 3.8749 (10) Å], forming a three-dimensional supramolecular network (Table 2 and Fig. 2).

S3. Refinement
Water H atoms were located in a difference map and refined with O-H and H···H distances restrained to 0.85 (1) and 1.39 (1) Å, respectively, and U iso (H) = 1.5U eq (O1W). All other H atoms were placed in calculated positions with C-H = 0.93 Å and U iso (H) = 1.2U eq (carrier C), and were refined in the riding-model approximation.  The molecular structure of the title complex. C-bonded H atoms have been omitted for clarity.

Figure 2
The packing diagram of the title complex, with the intermolecular hydrogen bonds denoted by dashed lines.