(Diethylenetriamine)bis(theophyllinato)zinc(II) dihydrate

In the title compound, [Zn(C7H7N4O2)2(C4H13N3)]·2H2O, the ZnII ion is pentacoordinated by three N atoms of the diethylenetriamine ligand and one N atom of each of the two theophyllinate anions in a distorted trigonal-bipyramidal geometry. The Zn—N distances range from 2.076 (3) to 2.221 (3) Å. The crystal packing is stabilized by O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds involving the theophylline and diethylenetriamine ligands and uncoordinated water molecules.

In the title compound, [Zn(C 7 H 7 N 4 O 2 ) 2 (C 4 H 13 N 3 )]Á2H 2 O, the Zn II ion is pentacoordinated by three N atoms of the diethylenetriamine ligand and one N atom of each of the two theophyllinate anions in a distorted trigonal-bipyramidal geometry. The Zn-N distances range from 2.076 (3) to 2.221 (3) Å . The crystal packing is stabilized by O-HÁ Á ÁO, O-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds involving the theophylline and diethylenetriamine ligands and uncoordinated water molecules.

S2. Experimental
To a suspension of theophylline (0.4 g, 2.22 mmol) in water (15 cm 3 ), diethylenetriamine (0.5 cm 3 ) was added. The obtained clear solution was mixed with a solution of Zn(CH 3 COO) 2 .2 H 2 O (0.2195 g, 1 mmol) in a diethylenetriaminewater mixture (1 cm 3 of diethylenetriamine in 5 cm 3 of water). The reaction mixture was stirred at 50°C for 30 min. and stored at room temperature over night. The white polycrystalline powder formed was collected by filtration, washed with aqueous diethylenetriamine (5%) and dried. Colourless single crystals were obtained by recrystallization from aqueous solutions after standing at room temperature 6 days.

S3. Refinement
All hydrogen atoms except those in the two water molecules were placed in calculated positions using a riding model, with C-H = 0.93-0.97 Å and with U iso = 1.5U eq (C) for methyl H and U iso = 1.2U eq (C) for aryl H. The methyl groups were allowed to rotate but not to tip. Hydrogen atoms from the two water molecules were found from difference map and refined with a restrained O-H distance of 0.82 (2) Å, 0.825 (19), 0.82 (2)Å and 0.814 (19) Å, respectively.

Figure 1
Molecular structure of the title compound with displacement ellipsoids at the 50% probability level.

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.