N,N′-Bis(pyrimidin-2-yl)terephthalamide dihydrate1

The organic molecule of the title compound, C16H12N6O2·2H2O, lies across a crystallographic inversion centre. The dihedral angle between the pyrimidine and benzene rings is 80.78 (6)°. The two pyrimidine rings are parallel by virtue of the centre of symmetry. The pyrimidine and benzene rings form dihedral angles of 41.41 (7) and 40.26 (7)°, respectively, with the amide plane. The molecules are linked by N—H⋯N and C—H⋯N hydrogen bonds into a two-dimensional network parallel to the (11) plane. O—H⋯O and C—H⋯O hydrogen bonds involving the water molecules link the adjacent layers into a three-dimensional network. In addition, a C—H⋯π interaction involving the benzene ring is observed.


The coordination chemistry of the title compound is under investigations.
Molecules of the title compound lie across a crystallographic inversion centre ( Fig. 1). All bond lengths and angles have normal values (Allen et al., 1987). The N,N-di-pyrimidin-2-yl-terepthalamide molecule has a staggered conformation. The orientation of the pyrimidine ring (C1-C4/N1/N2) with respect to the benzene ring (C6-C8/C6A-C8A) can be described by the dihedral angle formed by these planes of 80.78 (6)° and the torsion angle C4-N3-C5-C6 of −169.50 (11)°. The two pyrimidine rings are parallel by virtue of the centre of symmetry. The pyrimidine and benzene rings form dihedral angles of 41.41 (7)° and 40.26 (7)°, respectively, with the amide plane.
The structure shows O-H···O and C-H···O hydrogen bond between water and N,N-di-pyrimidin-2-yl-terepthalamide molecule. In the crystal packing (Fig. 2), the molecules are linked by N-H···N and C-H···N hydrogen bonds into a twodimensional network parallel to the (1 1 1) plane. The O-H···O and C-H···O hydrogen bonds (Table 1) involving the water molecules link the adjacent layers into a three-dimensional network. The crystal structure is further stablilized by C-H···π interactions involving the benzene ring (centroid Cg1).

Experimental
A solution of terepthaloyl chloride (203 mg, 1 mmol), in dry CH 2 Cl 2 (20 ml) was put in a round bottle flask under nitrogen atmosphere. 2-Aminopyrimidine (190 mg, 2 mmol) containing triethylamine (0.55 ml) in dry CH 2 Cl 2 (15 ml) was added dropwise. The reaction mixture was stirred at room temperature for 10 h. The reaction mixture was dried, washed with sodium bicarbonate solution, and then extracted with CH 2 Cl 2 (4 × 20 ml). The crude mixture was purified by column chromatography (silica gel, 100-200 mesh) using 20% ethyl acetate-petroleum ether solution as eluent to afford a white solid compound (188 mg, 65%). Single crystals of the title compound were grown by slow evaporation of a CHCl 3 -CH 3 OH (3:1 v/v) solution (m.p. 457-459 K).

Refinement
All H atoms were located from the difference map and isotropically refined. One of the water hydrogen atoms is disordered over two positions with occupancies each 0.50. The O-H distances were restrained to be equal within 0.03 Å. Fig. 1

Special details
Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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 > 2sigma(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.