catena-Poly[[bis(nitrato-κO)copper(II)]-bis[μ-1,4-bis(pyridin-3-ylmethoxy)benzene-κ2 N:N′]]

In the title compound, [Cu(NO3)2(C18H16N2O2)2]n, the CuII ion lies on an inversion center and is six-coordinated in a Jahn–Teller-distored octahedral geometry defined by four N atoms of the pyridine derivative forming a square plane, above and below which are the O atoms of the nitrate anion. The ligand links the metal atoms linto a linear chain running along the a axis. One of the nitrate O atoms is equally disordered over two sets of sites.

In the title compound, [Cu(NO 3 ) 2 (C 18 H 16 N 2 O 2 ) 2 ] n , the Cu II ion lies on an inversion center and is six-coordinated in a Jahn-Teller-distored octahedral geometry defined by four N atoms of the pyridine derivative forming a square plane, above and below which are the O atoms of the nitrate anion. The ligand links the metal atoms linto a linear chain running along the a axis. One of the nitrate O atoms is equally disordered over two sets of sites.

Related literature
For the synthesis and background to network structures built up from flexible pyridyl-based aromatic ligands and transition metals, see Liu et al. (2010a,b).

Experimental
Crystal data [Cu(NO 3

Comment
The bridging pyridyl ligands can be used to construct interesting 0D to three-dimensional supramolecular architectures.
Our group has reported some isolated molecule, chain, plane and three-dimensional network structures built up by flexible pyridyl-based aromatic ligands and transition metals. (Liu et al., 2010a;Liu et al., 2010b). As our continuing work for pyridyl ligands, we report here the synthesis and crystal structure of the title compound.
An asymmetric unit of the title compound consists of a 1,4-bis(pyridin-3-ylmethoxy)benzene molecule, a nitrate anion and a Cu II cation ( Figure 1). The Cu II cations lie on the inversion centers and are six-coordinated in the Jahn-Teller distored octahedral geometry environments defined by four N atoms forming the square planes and two O atoms locating the polar axis.
In the crystal, ribbon structures along [2 0 1] direction are built up by heterocyclic ligands bridging Cu II cations ( Figure   2, Table 1).

Experimental
The 1,4-bis(pyridin-3-ylmethoxy)benzene ligand was synthesized as the reference method (Liu et al., 2010a): A mixture of 1,4-dihydroxybenzene (1.1 g, 10 mmol), 3-chloromethylpyridine hydrochloride (3.28 g, 20 mmol) and NaOH (1.6 g, 40 mmol) in acetonitrile (50 ml) was refluxed under nitrogen with stirring for 24 h. After cooling to room temperature, the solution was filtered and the residue was washed with acetonitrile for several times. The mixed filtrate was droped into 300 ml water solution to get the powder crude product. A total of 2.51 g (yield 86%) pure product was obtained by recrystallizing from the mixed solution of 10 ml water and 10 ml me thanol. The title compound was synthesized by reaction of 1,4-bis(pyridin-3-ylmethoxy)benzene ligand (0.29 g, 1.0 mmol) and Cu(NO 3 ) 2 . 3H 2 O (0.22 g, 1.0 mmol) in 5 ml water and 5 ml me thanol mixed solution. After filtration, blue block crystals suitable for X-ray diffraction were obtained by slow evaporation at room temperature for several days in 46% yield.

Refinement
O4 atom of nitrate was disordered over two positions with site occupancy factors of ca 0.51 and 0.49, and then, the two positions were restraint refined with commond 'Iosr 0.01 O4 O4' '. H atoms bound to C atoms were placed in calculated positions and treated as riding on their parent atoms, with C-H = 0.93 Å (aromatic); C-H = 0.97 Å (methylene), and with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids at the 50% probability level for non-H atoms, disordered O4' atom has been omitted for clarity.