Tetraaquabis[N,N′-bis(pyridin-3-ylmethylidene)benzene-1,4-diamine]zinc dinitrate 1.49-hydrate

In the title compound, [Zn(C18H14N4)2(H2O)4](NO3)2·1.49H2O, the ZnII atom, lying on an inversion center, is coordinated by two N atoms from two N,N′-bis(pyridin-3-ylmethylidene)benzene-1,4-diamine ligands and four water molecules in a distorted octahedral geometry. The nitrate anion is disordered over two sets of sites, with an occupancy ratio of 0.744 (4):0.256 (4). The uncoordinated water molecule is also disordered with an occupancy factor of 0.744 (4). O—H⋯O and O—H⋯N hydrogen bonds link the complex cations, nitrate anions and uncoordinated water molecules into a supramolecular layer parallel to (102).

In the title compound, [Zn(C 18 H 14 N 4 ) 2 (H 2 O) 4 ](NO 3 ) 2 Á-1.49H 2 O, the Zn II atom, lying on an inversion center, is coordinated by two N atoms from two N,N 0 -bis(pyridin-3ylmethylidene)benzene-1,4-diamine ligands and four water molecules in a distorted octahedral geometry. The nitrate anion is disordered over two sets of sites, with an occupancy ratio of 0.744 (4):0.256 (4). The uncoordinated water molecule is also disordered with an occupancy factor of 0.744 (4). O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds link the complex cations, nitrate anions and uncoordinated water molecules into a supramolecular layer parallel to (102).

Related literature
For background to the design and synthesis of zinc complexes with Schiff-base ligands and their potential applications as fluorescent probes, see: Su et al. (1999); Ye et al. (2005). For the synthesis of the ligand, see: Ye et al. (2004).
metal-organic frameworks with unusual network patterns and novel properties can be achieved due to the specific geometry including the different relative orientation of N-donors and the zigzag conformation of the space moiety between the two terminal coordination groups. For background to the design and syntheses of zinc complexes with Schiff-base and their potential applications as fluorescent probes, see: Su et al. (1999);Ye et al. (2005).
In the title compound ( Fig. 1), the Zn II ion lies on an inversion center and is coordinated in a distorted octahedral geometry  (Table 1), forming a layer structure.

Experimental
The ligand L was prepared according to the previous method (Ye et al., 2004). 1,4-Diaminobenzene (2.14 mg, 10 mmol) was dissolved in methanol (20 ml), followed by addition of 3-pyridinecarboxaldehyde (4.24 mg, 40 mmol). The mixture was stirred at room temperature for 2 h and then filtered. The resulting yellow crystalline solid was washed with methanol several times and dried in air. A solution of Zn(NO 3 ) 2 (35.9 mg, 0.2 mmol) in acetonitrile (10 ml) was slowly layered onto a solution of L (117 mg, 0.625 mmol) in methylene chloride (12 ml). Diffusion between the two phases over two weeks produced colorless crystals of the title compound.