Aqua(pyridine-3-carboxylic acid-κN)(pyridine-2,6-dicarboxylato-κ3 O 2,N,O 6)copper(II) monohydrate

In the title CuII complex, [Cu(C7H3NO4)(C6H5NO2)(H2O)]·H2O, the environment of the Cu2+ ion is a distorted square pyramid with the axial site occupied by the O atom from the coordinated water molecule and the square base formed by two O and two N atoms from the tridentate anion and the neutral monodentate pyridine-3-carboxylic acid ligand. O—H⋯O hydrogen bonds, as well as π–π interactions [centroid–centroid distance = 3.945 (3) Å] contribute to the stabilization of this structure.

In the title Cu II complex, [Cu(C 7 H 3 NO 4 )(C 6 H 5 NO 2 )(H 2 O)]Á-H 2 O, the environment of the Cu 2+ ion is a distorted square pyramid with the axial site occupied by the O atom from the coordinated water molecule and the square base formed by two O and two N atoms from the tridentate anion and the neutral monodentate pyridine-3-carboxylic acid ligand. O-HÁ Á ÁO hydrogen bonds, as well asinteractions [centroidcentroid distance = 3.945 (3) Å ] contribute to the stabilization of this structure.

Related literature
For the use of transition-metal-carboxylate systems in supramolecular chemistry and functional materials, see: MacDonald et al. (2000); Siddiqui et al. (2008); Custelcean & Gorbunova (2005). For a description of the geometry of complexes with five-coordinate metal atoms, see: Addison et al. (1984).

Comment
In recent years, the chemistry of transition metal carboxylate systems is of great interest because of their extensive usage in supramolecular chemistry and functional materials (Custelcean & Gorbunova, 2005;MacDonald, et al., 2000;Siddiqui, et al., 2008). Here, we report a new Cu II complex with pyridine-2,6-dicarboxylic acid and pyridine-3-carboxylic acid.
In this complex, the Cu 2+ ion is coordinated by one oxygen atom from water molecule, two oxygen atoms from the dianion of pyridine-2,6-dicarboxylic acid, and two nitrogen atoms from pyridine-2,6-dicarboxylate and pyridine-3-carboxylic acid, respectively ( Fig. 1). Thus, the coordination environment of Cu 2+ ion is a distorted square pyramid, as indicated by τ value of 0.06 (Addison, et al., 1984). The asymmetric units are linked into three-dimensional structure through C-H···O and O-H···O hydrogen bonds and π-π interactions between the neighbouring pyridine rings with centroid-centroid distance of 3.945 (3) Å (Fig. 2).

Experimental
A mixture of Cu(CH 3 COO) 2 . H 2 O (0.5 mmol), pyridine-2,6-dicarboxylic acid (0.5 mmol), pyridine-3-carboxylic acid (0.5 mmol) in H 2 O (4 ml) and CH 3 OH (4 ml) was adjusted to pH ca 7.5 by triethylamine, sealed in a Teflon lined stainless steel container and heated at 140 °C for 3 days. After the sample was cooled to room temperature, blue crystals were collected with a yield of 30%.

Refinement
All H atoms were refined using a riding model. C-H values were set to 0.93 Å with U iso (H) =1.2 U eq (C), and O-H values were set to 0.82 to 0.85 Å with U iso (H) =1.5 U eq (N). Fig. 1. The molecular structure of the title complex, with atomic labels and 30% probability displacement ellipsoids for non-H atoms.

Figures
supplementary materials sup-2  as those based on F, and R-factors based on ALL data will be even larger.