Bis(4-aminobenzenesulfonato-κO)bis(propane-1,3-diamine-κ2 N,N′)copper(II) dihydrate

In the title compound, [Cu(C3H10N2)2(C6H6NO3S)2]·2H2O, the CuII atom lies on an inversion center and is hexacoordinated by four N atoms from two 1,3-diaminopropane ligands and two O atoms from two 4-aminobenzenesulfonate ligands in a trans arrangement, displaying a distorted and axially elongated octahedral coordination geometry, with the O atoms at the axial positions. A three-dimensional network is formed in the crystal structure through O—H⋯O, N—H⋯O and N—H⋯N hydrogen bonds.

In the title compound, [Cu(C 3 H 10 N 2 ) 2 (C 6 H 6 NO 3 S) 2 ]Á2H 2 O, the Cu II atom lies on an inversion center and is hexacoordinated by four N atoms from two 1,3-diaminopropane ligands and two O atoms from two 4-aminobenzenesulfonate ligands in a trans arrangement, displaying a distorted and axially elongated octahedral coordination geometry, with the O atoms at the axial positions. A three-dimensional network is formed in the crystal structure through O-HÁ Á ÁO, N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds.
This work was supported financially by the NSFC (grant No. 20801047), the Foundation of Xuzhou Normal University (07XLA07, KY2007039 and XGG2007034) and the 'Qing Lan' Project (08QLT001).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HY2252).

S1. Comment
Crystal engineering based on metal and organic building blocks has been rapidly developed in recent years owing to their novel and diverse topologies and potential applications in catalysis and host-guest chemistry (Evans & Lin, 2002).

Covalent bonds and hydrogen bonds have been demonstrated to be two important interactions in constructing metal-
containing supramolecular frameworks, and they have brought forth a great variety of novel frameworks with fascinating structural motifs (Li et al., 2003(Li et al., , 2004. 1,3-Diaminopropane (tn) ligand behaves as a strong chelatator in its metal complexes due to the formation of a stable six-membered ring. At the same time, it is a good H-bond donor due to the existence of amino groups (Sundberg et al., 2001). The crystal egineering of tn and carboxylate ligands has been studied in detail (Sundberg et al., 2001), but supramolecular chemistry of tn and 4-aminobenzenesulfonate (4-ABS) ligand is still not explored to that extent (Wang et al., 2002). 4-ABS can act as a bridging or a terminal ligand in its metal complexes.
On the other hand, studies on the coordination and supramolecular chemistry of 4-ABS have showed that it is a good Hbond acceptor and can form strong H-bonds due to its three O atoms and one N atom (Kim & Lee, 2002;Wang et al., 2002). In view of their excellent coordination capability and good H-bond donor or acceptor nature, we employed tn and 4-ABS as mixed organic building blocks to construct supramolecular networks in an expectation that these ligands may generate hydrogen bonding and/or covalent interactions with transition metal ions in the assembly process. Herein, we report the synthesis and structure of the title compound.
As shown in Fig. 1, the Cu II atom lies on an inversion center and is octahedrally coordinated by four N atoms from two tn ligands and two O atoms from two 4-ABS ligands in a trans arrangement. The coordination polyhedron of the Cu II ion can be described as axially elongated octahedral, with the O atoms at the axial positions. The tn ligand shows chelating coordination behavior and displays a chair conformation in the equatorial direction. This kind of coordination mode was also found in the similar complexes (Sundberg et al., 2001;Sundberg & Sillanpää, 1993;Sundberg & Uggla, 1997). The axial Cu-O distance is 2.589 (3) Å, indicating a weak coordination. The equatorial Cu-N1 and Cu-N2 bond lengths are 2.038 (3) and 2.029 (3) Å, respectively, which are much shorter than the axial Cu-O distance and very similar to those in the previously reported trans-bis(4-methylbenzenesulfonato)bis(1,3-diaminopropane)copper(II) (Sundberg & Sillanpää, 1993). The tn molecule forms a six-membered chelate ring with asymmetric Cu-N1-C1 and Cu-N2-C3 angles of 122.7 (2) and 119.9 (2)°. A plausible explanation for the deviations described above may be attributed to the asymmetric hydrogen bonding with respect to the chelate ring. The complex molecules are linked into a two-dimensional layer through hydrogen bonds between the uncoordinated water, the sulfonate group and the amino groups of the tn ligand. The layers are further connected into a three-dimensional network through hydrogen bonds between the amino groups and the sulfonate groups of neighboring 4-ABS ligands (Fig. 2).

S2. Experimental
Diaquabis(4-aminobenzenesulfonato)copper(II) dihydrate was synthesized according to the literature (Gunderman et al., 1996). 1,3-Diaminopropane (0.35 g, 4.72 mmol) in 10 ml water was dropped slowly into the stirred diaquabis(4-aminobenzenesulfonato)copper(II) dihydrate (1.12 g, 2.33 mmol) solution in 20 ml water. The mixed solution was kept stirring at room temperature for 30 min. After filtration, the filtrate was left to evaporate in air. After a few days, blue crystals of the title compound suitable for X-ray study were obtained (yield 0.70 g, 51%).

S3. Refinement
H atoms bonded to C atoms or N atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 (aromatic) and 0.97 (CH 2 ) Å and N-H = 0.90 and 0.86 Å and with U iso (H) = 1.2U eq (C,N). Water H atoms were located in a difference Fourier map and refined as riding, with O-H = 0.85 Å and with U iso (H) =1.5U eq (O).  The packing diagram of the title compound viewed along the b axis. H atoms not involved in hydrogen bonds (dashed lines) are omitted for clarity.