Aqua[2,2′-(propane-1,3-diyl)bis(5-carboxy-1H-imidazole-4-carboxylato)-κ4 N 3,O 4:N 3′,O 4′](pyridine-κN)cobalt(II)–4,4′-bipyridine (1/1)

In the title compound, [Co(C13H10N4O8)(C5H5N)(H2O)]·C10H8N2, the asymmetric unit comprises half a CoII complex located on a mirror plane and half a cocrystallized molecule of 4,4′-bipyridine located on an inversion center. The CoII ion is six coordinate, with distorted octahedral geometry, ligated by two N atoms and two O atoms from a 2,2′-(propane-1,3-diyl)bis(5-carboxy-1H-imidazole-4-carboxylate) dianion, one N atom from a pyridine molecule and one coordinating water molecule. The Co—O bond lengths range from 2.076 (2) to 2.1441 (15) Å, while the Co—N bond lengths are 2.138 (3) and 2.1515 (17) Å. A two-dimensional network of N—H⋯O and O—H⋯N hydrogen bonds stabilizes the crystal packing. There are π–π interactions between the bipyridine and imidazole rings [centroid–centroid distance = 3.7694 (4) Å]. The propane-1,3-diyl group is disordered over two conformations, with refined occupancies of 0.755 (8) and 0.245 (8).


Experimental
Crystal data [Co(C 13 Table 1 Hydrogen-bond geometry (Å , ).  As shown in Fig. 1, the molecule is a discrete neutral monomer, in which the asymmetric unit comprises half a CoII complex located on a mirror plane and half a co-crystallized molecule of 4,4′-bipyridine located on an inversion center.
The Co II ion is six coordinate and has a distorted octahedral geometry. It is ligated by two nitrogen atoms and two oxygen atoms from a 1,3-bis-(1H-imidazole-4,5-dicarboxylate) propane dianion, one nitrogen atom from a pyridine molecule and one oxygen atom from a coordinated water molecule. The Co-O distances range from 2.076 (2) to 2.1441 (15) Å, while Co-N distances are 2.138 (3) and 2.1515 (17) Å, respectively. A two-dimensional network of N-H···O and O-H···N hydrogen bonds help to stabilize the crystal packing. Aromatic π-π interactions between bipyridine rings and imidazole rings [centroid-centroid distance = 3.7694 (4) Å] are also observed.

Refinement
H atoms attached to N and O atoms were located in a difference Fourier maps and refined as riding in their as-found relative positions, with U iso (H) = 1.5U eq (O, N). Other H atoms were positioned geometrically with C-H = 0.93 and 0.97 Å for aromatic and methylene H, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound, showing 30% probability displacement ellipsoids. Unlabelled atoms are related to labelled atoms by the symmetry operations (x, -y+1/2, z for CoII complex; 1-x, 1-y, 1-z for 4,4-bipy). 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 Occ. (