Poly[aqua[μ3-4-carboxy-2-(pyridin-4-yl)-1H-imidazole-5-carboxylato-κ5 N 1,O 5:N 3,O 4:N 2]nickel(II)]

The water-coordinated Ni2+ cation in the title compound, [Ni(C10H5N3O4)(H2O)]n, assumes an octahedral NiN3O3 coordination mode and is N,O-chelated by two deprotonated 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid (HPyImDC2−) ligands, forming a layer structure extending in the bc plane. The chains are arranged along the b-axis direction, forming a layer structure extending in the bc plane. O—H⋯O hydrogen bonding between the layers results in the formation of a three-dimensional supramolecular framework. The structure is isotypic with the Zn analogue [Li et al. (2009). Cryst. Growth Des. 6, 3423–3431].

The water-coordinated Ni 2+ cation in the title compound, [Ni(C 10 H 5 N 3 O 4 )(H 2 O)] n , assumes an octahedral NiN 3 O 3 coordination mode and is N,O-chelated by two deprotonated 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid (HPyImDC 2À ) ligands, forming a layer structure extending in the bc plane. The chains are arranged along the b-axis direction, forming a layer structure extending in the bc plane. O-HÁ Á ÁO hydrogen bonding between the layers results in the formation of a three-dimensional supramolecular framework. The structure is isotypic with the Zn analogue [Li et al. (2009). Cryst. Growth Des. 6, 3423-3431].
As shown in Fig. 2a, the {NiN 3 O 3 } octahedra connect with the T-shaped HPyImDC 2anions to be a one-dimensional chain structure extending in the c direction. Then these one-dimensional chains arrange along the b direction to be a twodimensional layer structure extending in the bc plane ( Fig. 2 b), which are further connected through the hydrogen bonds , respectively, to construct a three-dimensional supramolecular framework ( Fig. 2c and Table 1).

Experimental
Preparation of the complex.
A solution of NiCl 2 6H 2 O (0.012 g, 0.5 mmol) and H 3 PyImDC (0.012 g, 0.05 mmol) in DMF (1 ml) and H 2 O (0.5 ml) was sealed into a 15 ml Teflon-lined stainless autoclave and heated at 433 K for 4 days and then cooled to room temperature gradually to afford well formed green block crystals in about 60% yield (based on Zn

Refinement
The H atoms bonded to C were positioned geometrically with C-H distance 0.93-0.96 Å, and treated as riding atoms, with . The H atoms bonded to O were located in a difference Fourier map and refined isotropically. Fig. 1. A view of the centrosymmetric molecule of (I), with displacement ellipsoids drawn at the 25% probability level [symmetry code: (i) -x, -y -1, -z; (ii) x, -y -1/2, z + 1/2; (iii) x, -y -1/2, z -1/2] (b) one-dimensional chains arranged in the b direction to be a two-dimensional layer structure; (c) the two-dimensional layers packed in an AAA way via hydrogen-bonding interactions to be a three-dimensional network.