supplementary materials

Many interesting in situ reactions such as hydrolysis (Lin et al., 1998; Evans et al., 1999; Lin et al., 2000; Sun et al., 2001), redox (Xiong et al., 1998; Ma et al., 1999; Evans et al., 2000; Tao et al., 2002), and dehydration (Gutschke et al., 2000) can occur under solvothermal environment. It has been found that cyano substituted aromatic compound can be hydrolyzed and the cyano group would be changed to carboxylic acid. For example, Lin's group reported that 3-cyanopyridine or 4-cyanopyridine undergoes a hydrolysis reaction to form 3-pyridinecarboxylic acid (Lin et al., 2000) and 4-pyridinecarboxylic acid (Evans et al., 1999), respectively; Hong's group revealed that the hydrolysis of 1,4-dicyanobenzene gives rise to 1,4-benzenedicarboxylate acid (Sun et al., 2001). The present example shows that 4-cyanobenzoic acid also undergoes a similar hydrolysis procedure.

The hydrothermal reaction of 4-cyanobenzoic acid, CuO, pyridine (py) and water under weak basified conditions gave rise to the title compound (1) as blue prismatic crystals, which were very easy to be efflorescent and become opaque when out of the mother liquid. The IR spectrum of (1) exhibits strong bands at 1605 and 1390 cm⁻¹, which are attributed to the Vas and Vas peaks of COO⁻ group, respectively. The absence of peaks in the range of 2240—2220 cm⁻¹ shows that there exists no cyano group in (1).

A single-crystal X-ray diffraction analysis revealed that compund (1) has a similar 1-D chain structure as that of CuL¹(py)₂(H₂O).py·H₂O (L¹ = 1,4-benzenedicarboxylate ligand; Ohmura et al., 2003). The crystallographically independent unit of (1) consists of one L¹ ligand, two py ligands, one copper(II) atom, one coordination water molecule and hemisemi lattice water molecule. As show in Fig. 1, each copper(II) atom is almost in a square-based pyramidal environment, of which the axial position is occupied by coordination water molecule O1w (Cu1—O1w = 2.243 (3) Å) and the square plane is defined by two nitrogen atoms from two py ligands (Cu—N = 1.996 (3) and 2.010 (3) Å), two oxygen atoms from two L¹ ligands (Cu—O = 1.931 (2) and 1.934 (2) Å) with an O24—Cu1—O22 bond angle of 178.3 (1) °. The bond angles of O1w—Cu1—X (X = the atoms in the square plane) vary from 89.4 (1) to 96.2 (1) °, which indicates that O1w is approximately perpendicular to the square plane. In this way, each L¹ ligand links two symmetry-related copper(II) atoms (Cu···Cu, ca 10.901 Å) into a 1-D chain along the c direction. Compound 1 crystallizes in space group P2₁2₁2₁, and the 1-D chain perfectly lies in the 2₁ axis. Hence, the 1-D chain is in a helical mode as the case found in the structure of [Cu(L²)(NO₃)₂]₈ (L² = 2,5-bis(2-pyridyl)-1,3,4-oxodiazole) (Bu et al., 2002). To the best of our knowledge, 1-D helical chiral compound with bridging L¹ ligands has only a reported example in the literature (Cutland et al., 2001).

Considering the short contacts shows that the neighboring parallel chains are interconnected by O—H···O hydrogen bonds [O1W···O21ⁱ = 2.735 (4) Å, O1w—Hw1···O21ⁱ = 133.7 (6) °; O1W···O23ⁱⁱ = 2.719 (3) Å, O1w—Hw2···O23ⁱⁱ = 165 (1)°; (i) x − 1, y, z; (ii) −0.5 − x, 1 − y, −1/2 + z. (Table 1)] to form a layer (Fig. 1). Each of these hydrogen bonds is established from an axially coordinated water molecule to one of the carboxylate group of a neighboring L¹ ligand. The distance of two adjacent chains agrees with the Cu1···Cu1a separation of ca 5.990 Å, which is shorter than the L¹-bridged Cu···Cu separation. However, considering the short contacts between two adjacent layers, only van der Waals interactions can be found (Fig. 2). The layers are crosswise arranged along the b direction to form a self-complementary structure (Seo et al., 2000) that apparently stabilizes the whole crystal structure. Uncoordinated water molecules locate in the channels along the a direction.