N,N,N′,N′-Tetrakis(pyridin-4-yl)methanediamine monohydrate

In the title compound, C21H18N6·H2O, two 4,4′-dipyridylamine groups are linked by a methylene C atom, which sits on a twofold axis. The lattice water molecule is located slightly off a twofold axis, and is therefore disordered over two positions. In the crystal, the organic molecules and the water molecule are linked by O—H⋯N hydrogen bonds. The organic molecules exhibit extensive offset face-to-face π–π interactions to symmetry equivalents [centroid–centroid distances = 3.725 (3) and 4.059 (3) Å].

In the title compound, C 21 H 18 N 6 ÁH 2 O, two 4,4 0 -dipyridylamine groups are linked by a methylene C atom, which sits on a twofold axis. The lattice water molecule is located slightly off a twofold axis, and is therefore disordered over two positions. In the crystal, the organic molecules and the water molecule are linked by O-HÁ Á ÁN hydrogen bonds. The organic molecules exhibit extensive offset face-to-faceinteractions to symmetry equivalents [centroid-centroid distances = 3.725 (3) and 4.059 (3) Å ].   Table 1 Hydrogen-bond geometry (Å , ).
construction of multidimensional metal-organic frameworks. These have potential applications in catalysis and as luminescent materials (Shin et al., 2012;Welbes & Borovik, 2005;Zeng et al., 2010). For example, as a building block, bis(4-pyridyl)amine (bpa) has been extensively used for self-assembly of multidimensional coordination polymers, because the ligand has significant functionalities, e.g. hydrogen bonding capability (Braverman & LaDuca, 2007;Shyu, et al., 2009). Thus, we have made a new ligand, N,N,N′,N′-tetra-4-pyridyl-methylenediamine (TPMD), which can be used as a building unit for self-assembly of potential luminescent materials and catalysts. Here, we report the synthesis and crystal structure of N,N,N′,N′-tetra-4-pyridyl-methylenediamine monohydrate.
The title compound in its crystalline state is centrosymmetric (Fig. 1). The dihedral angle between neighboring pyridyl rings is 63.74 (7)°, and the angle of N1-C11-N1(-x, y, 1.5 -z) is 114.5 (2)°. The water molecule appears to be slightly off a 2-fold axis, and was refined using a disordered model, which gave a lower R value and a flatter difference map compared to a non-disordered model. The crystal packing is stabilized by strong intermolecular O-H···N hydrogen bonds ( Table 1) that connect pairs of organic molecules by water molecules into chains along the (101) direction (Fig. 2).

Experimental
The title compound was prepared as follows. NaH (0.561 g, 0.0234 mol) was added carefully to a DMF solution (50 ml) of 4,4′-dipyridylamine (2.00 g, 0.0117 mol) and stirred for 2 days at room temperature. To the mixture was added dropwise dichloromethane (20 ml) and the mixture solution was again stirred for 2 days, which resulted in a dark red solution. Then the mixture was quenched with H 2 O (50 ml), and the organic layer was extracted with CHCl 3 (3 times, 100 ml). The extract was washed with NaCl solution to purify and then dried with Na 2 SO 4 . After removing the organic solvent, a pale yellow oil was obtained, from which colorless crystals formed in 1 day. The crystals were filtered and washed with n-hexane and acetonitrile. Yield: 0.86 g (42%

Refinement
The H atom of O1 was located in a difference Fourier map and refined isotropically. parameters of the parent C atoms.

Figure 1
An ellipsoid plot (40% probability) of the title compound. The unlabelled half of the molecule is related by a crystallographic 2-fold axis. The water molecule is disordered about a 2-fold axis (for clarity, only one component is shown).  A view of the title compound showing offset face-to-face π-π interactions.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (