supplementary materials

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, 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 H-bond 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).