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

In the title compound, [Co(NO3)2(C18H16N2O2)2]n, the CoII ion is located on an inversion center and is six-coordinated in an octahedral environment defined by four N atoms of the pyridine rings and two O atoms of the nitrate anions. The ligands link the CoII ions into a linear chain running along [201]. One O atom of the nitrate ligand is disordered over two positions with site-occupancy factors of 0.59 (4) and 0.41 (4).

In the title compound, [Co(NO 3 ) 2 (C 18 H 16 N 2 O 2 ) 2 ] n , the Co II ion is located on an inversion center and is six-coordinated in an octahedral environment defined by four N atoms of the pyridine rings and two O atoms of the nitrate anions. The ligands link the Co II ions into a linear chain running along [201]. One O atom of the nitrate ligand is disordered over two positions with site-occupancy factors of 0.59 (4) and 0.41 (4).

Comment
The bridging compounds with rigid and flexible pyridyl-containing bidentate or multidentate organic spacers have assemble numerous interesting topology structures by coordination with metals and intermolecular supramolecular interaction. Our group focus attention on study of flexible pyridyl-based aromatic ligands, and obtained some isolated molecule, chain, plane and three-dimensional network structures (Liu et al., 2010a;Liu et al., 2010b;Yu et al., 2010). Herein, as a continuing work for pyridyl ligands, we report the synthesis and crystal structure of the title compound, which is a isomorphic compound of our previous report (Zou et al., 2011).
An asymmetric unit of the title compound consists of a 1,4-bis(pyridin-3-ylmethoxy)benzene molecule, a nitrate anion and a Co II cation ( Figure 1). The Co II cation lie on an inversion center and is six-coordinated in the octahedral geometry environment defined by four N atoms of the pyridine derivatives and two O atoms of the nitrate anions (Table 1).
In the crystal, ribbon structures along [2 0 1] direction are built up by N-heterocyclic ligands linking Co II cations ( Figure   2).

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 Co(NO 3 ) 2 . 6H 2 O (0.29 g, 1.0 mmol) in 5 ml water and 5 ml me thanol mixed solution, and filtered after stirring for about 1 h. The filtate allowed to stand for four days under the room temperature to obtain pink block-like crystals suitable for X-ray analysis.