supplementary materials

The design and syntheses of supramolecular complexes exhibiting novel structures and their properties have provided exciting new prospects for chemists (Wang et al., 2008). To date, a number of monometallic extended inorganic-organic composite materials have been synthesized by the combination of organic spacers and inorganic metal salts (Lan et al., 2009). The rational design and construction of complexes greatly depend on the judicious selection of the organic ligands and proper choice of metal centers. Among various ligands, the versatile carboxylic acid ligands exhibiting diverse coordination modes, have been well used in the preparations of various metal-organic complexes, which exhibit interesting applications as functional materials (Hou et al., 2004). 1,2,3-Benzothiadiazole-7-carboxylic acid (HL) known as a disease-resistance activator of plant is a versatile carboxylic acid ligand containing N and S donors for the following reasons: (1) HL has a group –COOH and a thiadiazole ring, in which the O, N and S atoms all could coordinate to metal ions. So HL can act as a bridging ligand. (2) The large conjugated π system of benzothiadiazole ring may act as the directing group for π···π stacking and C—H···π interactions. (3) Both N and O atoms in HL being typical electron donor in forming hydrogen bond, therefore may construct H-bonded supramolecular framework. However, up to now, HL has been largely ignored by coordination chemists and it has not been used for the preparation of metal complexes. We report herein the preparation and crystal structure of the title complex.

In the polymeric title complex, each Cu atom is surrounded by three 1,2,3-benzo- thiadiazole-7-carboxylate and two water molecules. A 1,2,3-benzothiadiazole-7 -carboxylate ligand bridges the two Cu atoms (Fig. 1) with a Cu···Cu distance of 9.006 (2) Å. The four O atoms (O1, O1W, O2W and O4ⁱ) [symmetry code (i): x - 1, y, z] in the equatorial planes around each Cu atom form a distorted square-planar arrangement, while the distorted square-pyramidal coordination is completed by the symmetry related N atoms of the bridging 1,2,3-benzothiadiazole -7-carboxylate ligands (Fig. 2).

In general, several parameters are often used to define the coordination geometries of the penta-coordinated metal centers, and one of the most common parameters is the τ factor defined by Addison et al. (τ = 0 for perfect square-pyramid environment and τ = 1 for trigonal bipyramidal geometry) (Addison et al., 1984). For the title compound, the calculated τ value is 0.173, which corresponds to an approximately square-pyramidal coordination environment.

The Cu-O and Cu-N bonds (Table 1) are in good agreement with the coreesponding values reported for Cu-carboxylate, [Cu(H₂O)₂], and Cu-thiadiazole complexes (Lukashuk et al., 2007; Qin et al., 2009). To the best of our knowledge, there is no report on the crystal structures of metal complexes of 1,2,3-thiadiazole, except of a molybdenum pentacarbonyl complex of 4-phenyl-1,2,3-thiadiazole (Batzel & Boese, 1981) and a silver tetrafluoroborate complex of 2-(1,2,3-thiadiazol-4-yl)pyridine (Richardson & Steel, 2002).

In the crystal structure, strong intermolecular O-H···O and O-H···N hydrogen bonds (Table 2) link the molecules into a three-dimensional supramolecular network, in which they may be effective in the stabilization of the structure.