Aqua[1-(4-carboxyphenyl)-1H-imidazole-κN 3](pyridine-2,6-dicarboxylato-κ3 O 2,N,O 6)copper(II) monohydrate

In the title complex, [Cu(C7H3NO4)(C10H8N2O2)(H2O)]·H2O, the CuII ion is in a slightly distorted square-pyramidal geometry. Two carboxylate O atoms and one pyridine N atom from a pyridine-2,6-dicarboxylate ligand chelate the CuII ion, forming two stable five-membered metalla rings. One imidazole N atom from a 1-(4-carboxyphenyl)imidazole ligand and one water molecule complete the five-coordination. O—H⋯O hydrogen bonds involving the coordinated water molecules and carboxylate groups link the complex molecules into chain-containing dinuclear macrocycles. O—H⋯O hydrogen bonds involving the uncoordinated water molecules link the chains into a layer extending parallel to (10).

In the title complex, [Cu(C 7 H 3 NO 4 )(C 10 H 8 N 2 O 2 )(H 2 O)]ÁH 2 O, the Cu II ion is in a slightly distorted square-pyramidal geometry. Two carboxylate O atoms and one pyridine N atom from a pyridine-2,6-dicarboxylate ligand chelate the Cu II ion, forming two stable five-membered metalla rings. One imidazole N atom from a 1-(4-carboxyphenyl)imidazole ligand and one water molecule complete the five-coordination. O-HÁ Á ÁO hydrogen bonds involving the coordinated water molecules and carboxylate groups link the complex molecules into chain-containing dinuclear macrocycles. O-HÁ Á ÁO hydrogen bonds involving the uncoordinated water molecules link the chains into a layer extending parallel to (101).   Table 1 Hydrogen-bond geometry (Å , ).

D-HÁ
Symmetry codes: (i) Àx; Ày þ 1; Àz þ 1; (ii) Àx þ 1; Ày þ 2; Àz þ 2; (iii) Àx; Ày þ 2; Àz þ 1.  2009;Yang et al., 2008). The introduction of N atoms can satisfy the coordination requirements of metal ions and they also link metal-carboxylate frameworks into various fascinating extended networks. On the other hand, N atoms are highly accessible to transition metal ions, their stronger coordination ability than carboxylate groups may result in the formation of hydrogen bonding interactions by uncoordinated carboxylate O atoms, which further make the whole framework more stable. Among N-containing carboxylate ligands, we are interested in pyridine-2,6-dicarboxylic acid (2,6-H 2 pydc) since its N atom and two carboxylate groups may chelate one metal ion, forming two stable five-membered rings (Li et al., 2008).
As shown in Fig. 1, the Cu II ion has a slightly distorted square-pyramidal coordination geometry. Two carboxylate O atoms and one pyridine N atom from a 2,6-pydc ligand and one imidazolyl N atom from HIBA are in the basal plane, with a mean deviation of 0.0222 (2) Å from the plane. Cu1 atom is slightly out of the plane about 0.2221 (3) Å. One water molecule (O1W) occupies the apical position. As expected, two O atoms (O4, O6) from different carboxylate groups and an N atom (N3) chelate Cu1, forming two stable five-membered rings. This results in Cu1-N3 bond distance of 1.9075 (17) Å being much shorter than Cu1-N1 bond distance of 1.9467 (18) Å. Two carboxylate groups (O3, O4, C11 and O5, O6, C17) are almost coplanar with the pyridine ring, with dihedral angles between them of 3.5 (1) and 7.3 (2)°, respectively.
HIBA serves as a monodentate ligand through imidazolyl N atom coordinating to Cu1 atom. The twisting angle between the imidazolyl ring and benzene ring is 23.02 (8)°, while the dihedral angle between the benzene ring and the carboxylate group in HIBA is 2.7 (2)°.
Interestingly, carboxylic proton forms a strong hydrogen bond with one uncoordinated carboxylate O atom of the 2,6-pydc ligand (Table 1), which results in a dinuclear supramolecular macrocycle (Fig. 2). The Cu···Cu separation in the cycle is 13.749 (2) Å. O-H···O hydrogen bonds between the other carboxylate group of the 2,6-pydc ligand and the coordinated supplementary materials sup-2 water molecule link the macrocyles into a one-dimensional supramolecular chain (Fig. 3). The nearest Cu···Cu separation in the chain is 6.322 (1) Å. O-H···O hydrogen bonds involving the uncoordinated water molecules link the chains into a layer.

Experimental
A mixture of pyridine-2,6-dicarboxylic acid (0.034 g, 0.2 mmol), HIBA (0.038 g, 0.2 mmol), copper nitrate hydrate (0.036 g, 0.2 mmol) and one drop of KOH aqueous solution (10%) in 15 ml distilled water was heated in a 30 ml Teflon-lined steel bomb at 433 K for 3 d. Blue crystals formed were collected, washed with ethanol and dried in air.

Refinement
All H atoms were located from difference Fourier maps and refined isotropically, with a distance restraint of O-H = 0.82 (1) Å. Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.