Diaquabis{5-carboxy-2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4-carboxylato}zinc

In the title compound, [Zn(C8H6N5O4)2(H2O)2], the six-coordinate ZnII ion, which is located on an inversion center, has a distorted octahedral configuration. Each 5-carboxy-2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4-carboxylate ligand chelates to the ZnII ion through a triazole N atom and a carboxylate O atom in the equatorial plane. The coordination sphere is completed by two water molecules in axial positions. There is an intramolecular O—H⋯O hydrogen bond in the ligand. In the crystal, molecules are linked via intermolecular O—H⋯O, O—H⋯N and N—H⋯N hydrogen bonds, forming a three-dimensional structure.

In the title compound, [Zn(C 8 H 6 N 5 O 4 ) 2 (H 2 O) 2 ], the sixcoordinate Zn II ion, which is located on an inversion center, has a distorted octahedral configuration. Each 5-carboxy-2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4-carboxylate ligand chelates to the Zn II ion through a triazole N atom and a carboxylate O atom in the equatorial plane. The coordination sphere is completed by two water molecules in axial positions. There is an intramolecular O-HÁ Á ÁO hydrogen bond in the ligand. In the crystal, molecules are linked via intermolecular O-HÁ Á ÁO, O-HÁ Á ÁN and N-HÁ Á ÁN hydrogen bonds, forming a three-dimensional structure.

Related literature
For the assembly of multi-functional ligands with metal ions in the construction of two-and three-dimensional structures with special properties such as electrical conductivity, magnetism, host-guest chemistry, and catalysis, see: Eddaoudi et al. (2001). For metal complexes with N-containing ligands, such as 4,4bipyridine and triazoles, see: Chang et al. (2010). For triazole derivatives complexed to Ru to form antitumor metal complexes, see: Komeda et al. (2002). For a silver(I) complex with a ligand containing both a carboxylate and a triazole group, see: Xie et al. (2009). For the isostructural manganese(II) complex of the same ligand, see: Ding & Tong (2010).

Comment
The assembly of multifunctional ligands with metal ions is currently of great interest due to their use in constructing two-and three-dimensional compounds with special properties (Eddaoudi et al., 2001). So far, most of these multi-dimensional coordination compounds are formed with N-containing ligands, such as, 4,4-bipyridine, polycarboxylic, and triazoles (Chang et al., 2010). Triazole derivatives have been studied as anti-inflammatory drug candidates and have also been used as ligands for binding Pt and Ru to form antitumor metal complexes (Komeda et al., 2002).
A system taking advantage of the presence of both a carboxylate and a triazol group for coordintaion to silver(I) has been reported on by (Xie et al., 2009). The isostructural manganese(II) complex of the title ligand, 2-(1H-1,2,4-triazol-1yl)methyl]-1H-imidazole-4,5-dicarboxylic acid, has been reported on by (Ding & Tong, 2010). Herein, we report on the synthesis and crystal structure of the title zinc(II) complex.
In the crystal, molecules are linked via intermolecular O-H···O, O-H···N and N-H···N hydrogen-bonds, to form a three-dimensional structure (Table 1).

Diaquabis{5-carboxy-2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4-carboxylato}zinc
Crystal data [Zn(C 8  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.