catena-Poly[[bis-(3,5-dicarboxy-benzo-ato)cobalt(II)]-μ-4,4'-bipyridine].

In the title compound, [Co(C(9)H(5)O(6))(2)(C(10)H(8)N(2))](n), the asymmetric unit consists of one Co(2+) ion with site symmetry 2, one mono-deprotonated 1,3,5-benzene-tricarboxylic acid anion and one-half of a 4,4'-bipyridine (4,4'-bipy) mol-ecule, in which two N and two C atoms have site symmetry 2. In the crystal structure, the Co(2+) centre is coordinated by four O atoms from two bidentate carboxyl-ate groups of two anions and two N atoms of two 4,4'-bipy mol-ecules, resulting in infinite chains propagating in [010]. The cobalt coordination is distorted trans-CoO(4)N(2) octa-hedral and inter-chain O-H⋯O hydrogen bonds complete the structure.

In the title compound, [Co(C 9 H 5 O 6 ) 2 (C 10 H 8 N 2 )] n , the asymmetric unit consists of one Co 2+ ion with site symmetry 2, one mono-deprotonated 1,3,5-benzenetricarboxylic acid anion and one-half of a 4,4 0 -bipyridine (4,4 0 -bipy) molecule, in which two N and two C atoms have site symmetry 2. In the crystal structure, the Co 2+ centre is coordinated by four O atoms from two bidentate carboxylate groups of two anions and two N atoms of two 4,4 0 -bipy molecules, resulting in infinite chains propagating in [010]. The cobalt coordination is distorted trans-CoO 4 N 2 octahedral and interchain O-HÁ Á ÁO hydrogen bonds complete the structure.

S1. Comment
Recently, many efforts in coordination chemistry and crystal engineering have been devoted to the construction of metalorganic coordination polymers (MOCPs) employing both coordination bonds and/or hydrogen bonds, due to their appropriate strength and directionality (Feller et al. 2007). Dual-ligand or multidentate organic ligands are usually engaged in the construction of MOCPs, among which carboxylates and N,N-bidentate ligands are all the simplest connectors potentially able to bridge metal ions (Brown et al. 2008). Herein, we report the title compound (I) containing organic dual-ligands (Fig. 1).
The structure of (I) presents a one-dimensional infinite chain (Fig.2), in which the Co 2+ centre (site symmetry 2) is coordinated by four O atoms from two bidentate carboxylate groups of two 1,3,5-benzenetricarboxylic acid anions, two N atoms of two 4,4′-bipyridine molecules. The Co 2+ caion resides in a distorted octahedral configuration. In the equatorial plane, it is chelted by four carboxylate oxygen atoms (O1, O2 and their symmetry equivalents) from two 1,3,5-benzenetricarboxylic acid anions (Table 1), in which the Co-O distances are very different.
In addition, these one-dimensional chains are linked together by O-H···O hydrogen bonds between carboxylate groups generating a three-dimensional framework ( Fig. 3 and Table 2).

S3. Refinement
The O-bound H atoms were located in difference Fourier maps and refined as riding in their as-found relative positions with U iso (H) = 1.5U eq (O). The C-bound H atoms were geometrically placed (C-H = 0.93Å) and refined as riding, U iso (H) = 1.2U eq (C). supporting information sup-2 Acta Cryst. (2008). E64, m1400

Figure 1
Asymmetric unit of (I), showing displacement ellipsoids at the 50% probability level for the non-hydrogen atoms.

Figure 2
One-dimensional chain structure of (I). H atoms are omitted for clarity. Displacement ellipsoids are drawn at the 50% probability level.  Three-dimensional structure of (I) arising by means of hydrogen bonds. Displacement ellipsoids are drawn at the 50% probability level.

catena-Poly[[bis(3,5-dicarboxybenzoato)cobalt(II)]-µ-4,4′-bipyridine]
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq