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

In the title compound, [Mn(C8H6N5O4)2(H2O)2], the MnII ion is situated on an inversion center and is six-coordinated by two N and two O atoms from two L ligands (HL = 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4,5-dicarboxylic acid) and two water molecules in a distorted octahedral geometry. In ligand L, the imidazole and triazole rings form a dihedral angle of 74.25 (8)°. Molecules are assembled into a three-dimensional structure via intermolecular O—H⋯O, O—H⋯N and N—H⋯N hydrogen-bonds, and π–π interactions with a short distance of 3.665 (2) Å between the centroids of the imidazole and triazole rings of neighbouring molecules.

In the title compound, [Mn(C 8 H 6 N 5 O 4 ) 2 (H 2 O) 2 ], the Mn II ion is situated on an inversion center and is six-coordinated by two N and two O atoms from two L ligands (HL = 2-[(1H-1,2,4triazol-1-yl)methyl]-1H-imidazole-4,5-dicarboxylic acid) and two water molecules in a distorted octahedral geometry. In ligand L, the imidazole and triazole rings form a dihedral angle of 74.25 (8) . Molecules are assembled into a threedimensional structure via intermolecular O-HÁ Á ÁO, O-HÁ Á ÁN and N-HÁ Á ÁN hydrogen-bonds, andinteractions with a short distance of 3.665 (2) Å between the centroids of the imidazole and triazole rings of neighbouring molecules.

Comment
Multidentate ligands containing rich coordination sites (N and/or O donors) are often employed to produce polymeric networks with structural diversity owing to their various coordination modes (Lee et al., 2005;Ouellette et al., 2007;Won et al., 2007). As ligands with multiple coordination sites, 1,2,4-triazole and its derivatives have been shown to be good organic linkers in generation of structurally versatile metal-organic frameworks since it can bridge different metal centers to afford coordination polymers that exhibit extraordinary structural diversity and facile accessibility of functionalized materials. We selected a ligand containing 1,2,4-triazole, imidazole, and carboxylate groups, 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4,5-dicarboxylic acid, to study its coordination chemistry. As a result, we report herein the crystal structure of the title compound (I).
In (I), Mn II ion located on an inversion center is six-coordinated by two imidazole nitrogen atoms (N4), two carboxylate group oxygen atoms (O1) from two ligands, and two water oxygen atoms (Fig. 1). The coordination bond lengths Mn-N and Mn-O are 2.248 (1), 2.186 (1) Å and 2.188 (2) Å, respectively. The coordination geometry around Mn II is a distorted octahedron -the Mn II coordination angles are in the range from 75.75 (6)° to 180.00 (1)°. Each L acts as a bidentate ligand.
In the crystal structure, the intra-and intermolecular hydrogen bonds (Table 1) and π-π interactions with short distance of 3.665 (2) Å between the centroids of imidazole and triazole rings from the neighbouring molecules consolidate the crystal packing.

Experimental
All solvents and chemicals were of analytical grade and were used without further purification. The compound [MnL 2 (H 2 O) 2 ] was synthesized as follows: 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4,5-dicarboxylic acid (1.0 mmol) was added to 5 cm 3 water and the resulting solution was adjusted pH to 7.0 by NaOH aqueous. Then MnCl 2 (0.5 mmol) was added to the above solution, and the mixture was stirred for 30 min and filtered. After one days, pink single crystals suitable for X-ray analysis were obtained. Analysis calculated (%) for C 16