Bis[6-(1H-benzimidazol-2-yl-κN 3)pyridine-2-carboxylato-κ2 N,O]cobalt(II) dihydrate

In the title compound, [Co(C13H8N3O2)2]·2H2O, the CoII atom has a distorted octahedral environment defined by four N atoms and two O atoms from two 6-(1H-benzimidazol-2-yl)pyridine-2-carboxylate ligands. In the crystal, the complex molecules and uncoordinated water molecules are linked via N—H⋯O and O—H⋯O hydrogen bonds, forming a two-dimensional supramolecular structure parallel to (010). π–π interactions are present between the imidazole, pyridine and benzene rings [centroid–centroid distances = 3.528 (2), 3.592 (2), 3.680 (2) and 3.732 (3) Å].


Experimental
Crystal data [Co(C 13 Table 1 Hydrogen-bond geometry (Å , ).  (Chun et al., 2005;Tranchemontagne et al., 2009). The structures and properties of such systems depend on the coordination and geometric preferences of both the central metal ions and bridging building blocks, as well as on the influence of weaker non-covalent interactions, such as hydrogen bonds and π-π stacking interactions. Multidentate ligands containing rich coordination sites (N and/or O donors) are often employed to produce polymeric networks with structural diversity owing to their various coordination modes (Eubank et al., 2011;Wang et al., 2009). Recently, we obtained the title mononuclear complex by the reaction of cobalt chloride with 6-(1H-benzimidazol-2-yl)pyridine-2-carboxylic acid using hydrothermal methods and its crystal structure is reported here.

Experimental
The synthesis was performed under hydrothermal conditions. A mixture of CoCl 2 .6H 2 O (0.2 mmol, 0.050 g), 6-(1H-benzimidazol-2-yl)pyridine-2-carboxylic acid (0.4 mmol, 0.098 g), NaOH (0.4 mmol, 0.016 g) and H 2 O (15 ml) in a 25 ml stainless steel reactor with a Teflon liner was heated from 293 to 433 K in 2 h and a constant temperature was maintained at 433 K for 72 h. After the mixture was cooled to 298 K, pink crystals of the title compound were recovered from the reaction.

Refinement
H atoms on C and N atoms were positioned geometrically and refined as riding atoms, with C-H = 0.95 and N-H = 0.88 Å and with U iso (H) = 1.2U eq (C, N). H atoms of the water molecules were located from a difference Fourier map and refined as riding, with U iso (H) = 1.5U eq (O). Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 )