Crystal structure of bis(1,3-diaminopropane-κ2 N,N′)bis[2-(4-nitrophenyl)acetato-κO]zinc(II)

In the structure of the title compound, [Zn(C8H6NO4)2(C3H10N2)2], the ZnII atom is located on a center of symmetry with one independent Zn—O distance of 2.199 (2) Å, and two Zn—N distances of 2.157 (2) and 2.144 (2) Å. The overall coordination geometry around the ZnII atom is octahedral. Several types of hydrogen-bonding interactions are evident. Both intramolecular [2.959 (3) Å] and intermolecular [3.118 (3) and 3.124 (3) Å interactions occur between the O atoms of the acetate group and the amino N atoms, and weak intermolecular C—H—O interactions involving the nitro groups, leading to an extended chain of the molecules aligned along the ac plane.


S1. Chemical context
The structure shows a weak N-H···O intramolecular H-bonding interaction involving a N atom of the diaminopropane ligand and an O atom of the nitrophenylacetic acid ligand. Additional intermolecular N-H···O H-bonding interactions involving these same ligands are also present. Several weak intermolecular H-bonding interactions of the C-H-O type also exist involving the nitro groups and neigbouring phenyl protons. The asymmetric unit consist of half of the molecule as the Zn atom is located at center of symmetry.

S2. Structural commentary
The structure shows a weak H-bond intramolecular N-H···O interaction involving the N atoms of the diaminopropane ligand and the O atoms of nitrophenylacetic acid ligand. Several weak intermolecular H-bonding interactions of the C-H -O type also exist involving the nitro groups and neigbouring C-H protons. The asymmetric unit consist of half of the molecule as the Zn atom is located at center of symmetry.

S3. Supramolecular features
H-atoms were placed in calculated positions and allowed to ride during subsequent refinement, with U iso (H) = 1.2U eq (C) and C-H distances of 0.93 Å for aromatic hydrogens, U iso (H) = 1.2U eq (C) and C-H distances of 0.97 Å for secondary methyl hydrogens, and U iso (H) = 1.2U eq (N) and N-H distances of 0.90 Å for amino hydrogens.

S4. Synthesis and crystallization
Undergraduate student participants enrolled in an open inquiry laboratory (OIL) course conducted the synthesis and charcterization procedures. 0.2 mmol (27.2 mg) of anhydrous ZnCl 2 , 0.4 mmol (29.7 mg) of 1,3-diaminopropane, and 0.4 mmol (72.5 mg) of 4-nitrophenylacetic acid were weighed and added into a 25-mL round-bottom flask containing 10 mL of 1:1 CH 3 CN/H 2 O mixture. The flask was connected to a condenser and placed on a sand bath and refluxed for 1 hr. The flask was then removed from the sandbath and cooled to room temperature. After filtering the solution, the clear supernatant was collected, and covered with a parafilm for slow evaporation. Single crystals suitable for X-ray measurement were found after several days.

S5. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1.

Figure 1
A thermal ellipsoid diagram of the title compound.

Figure 2
A packing diagram of the title compound.
supporting information

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.