supplementary materials

1H-Pyrazole and its 3,5-substituted derivatives have been widely used as bridging ligands in molecular magnetism and supramolecular chemistry because of their marked tendency to form high nuclearity species exhibiting specific magnetic properties (Krämer et al., 2002; Seredyuk et al., 2007). Copper complexes containing pyrazole-based ligands are of particular interest in bioinorganic chemistry, as they can be used as models for the active sites in copper proteins like hemocyanine and tyrosinase (Krämer, 1999; Raptis et al., 1999). In addition, copper carboxylates are important in biology and also in basic inorganic chemistry (Halcrow, 2001; Jain et al., 2004). The carboxylates show a large variety of coordination modes, which can lead to the formation of different assemblies, including supramolecular coordination polymers or metal–organic frameworks (Fritsky et al., 1993, 1994a,b; Skopenko et al., 1990). A large number of copper(II) carboxylates with flexible connection are reported (Barooah et al., 2006; Pradeep et al., 2006). Total use of 1H-pyrazole derivatives and carboxylates can lead to the formation of mononuclear complexes with vacant donor atoms, which can be use as building blocks for the preparation of polynuclear complexes or coordination polymers.

The title compound is a mononuclear complex (Fig. 1), which consists of a Cu^II ion as the central atom possessing a Jahn–Teller distorted tetragonal–bipyramidal environment. The four equatorial positions are occupied by two N atoms belonging to two monodentately coordinated 3,5-dimethyl-1H-pyrazole molecules [Cu—N = 1.9851 (18) and 1.9925 (16) Å] and two O atoms from the acetate anions [Cu—O = 1.9909 (15) and 2.0045 (14) Å]. The other two O atoms of the acetate anions occupy the axial positions [Cu—O = 2.4603 (16) and 2.4774 (18) Å] (Table 1). Each sort of ligands (3,5-dimethyl-1H-pyrazole and carboxylate) in the coordination sphere of central Cu^II is cis-oriented with respect to each other. According to the carboxylate coordination criteria (Poray-Coshits, 1980), the acetate anions of the title compound coordinate in a pseudo-chelate mode, forming a four-membered chelate ring. The specific chelation of the above mentioned acetate anions, when one of the two bonds always resides in the equatorial position and second bond occupies the axial position of tetragonal–bipyramidal environment, was found in many Cu^II compounds (Deka et al., 2006; Karmakar et al., 2007). The Cu—O equatorial distances varying in the range of 1.970 and 1.974 Å are somewhat shorter than those in the title compound. The axial Cu—O bond lengths in the title compound are less than 2.685 Å (Karmakar et al., 2007), but longer than 2.281 Å reported by Deka et al. (2006). In addition, asymmetric chelation of the acetate anions shows up in inequivalence of the two C—O bonds. Thus, C—O distances adjacent to the elongated axial Cu—O bonds [C13—O4 = 1.250 (3) and C11—O2 = 1.256 (2) Å] are a bit shorter than those in the equatorial plane [C13—O3 = 1.262 (3) and C11—O1 = 1.266 (3) Å]. The values of the angles around the central atom deviate from ideal tetragonal–bipyramidal geometry.

In the crystal packing (Fig. 2), the complex molecules are connected through intermolecular N—H···O hydrogen bonds into a one-dimensional linear chain. The hydrogen bonds in the structure are of two types, with distances N2···O4 = 2.726 (3) and N4···O2 = 2.732 (2)Å (Table 2). Each couple of hydrogen bonds of one type takes part in forming the different ten-membered cycles. Due to this crystal packing, the shortest intra-chain Cu···Cu separations are 6.018 and 6.123 Å.