A two-dimensional manganese(II) complex: poly[bis(μ2-4,4′-bipyridyl)tetrakis(μ2-3,5-dinitrobenzoato)dimanganese(II)]

The Mn atom in the title compound, [Mn2(C7H3N2O6)4(C10H8N2)2]n, is six-coordinated by two N atoms and four O atoms, forming a distorted octahedral geometry. The Mn—O bond lengths are in the range 2.1281 (13)–2.2011 (12) Å and the Mn—N bond lengths are 2.269 (2) and 2.278 (2) Å. Mn(II) atoms are double-bridged along the a axis by two pairs of bi-monodentate carboxyl groups, forming a double-stranded chain, while the bidentate 4,4′-bipyridine ligand bridges the Mn atom along the b axis. This results in a two-dimensional structure constructed of oblong grids with the sides of length 11.634 and 5.075 Å


Related literature
In order to study the relationship between the manganese ion and the biological coordination agent, the role of the manganese ion in the active sites and the structure of the active sites in the manganese enzymes, small molecule complexes are often applied to modeling the structure and the properties of reaction in the active centers, see: Shi et al. (2000). The characterization of metal complexes containing monocarboxylic acids has demonstrated the versatility of the carboxylate group as an innersphere ligand, see: Mehrotra & Bohra (1983).

Comment
In order to study the relationship between the manganese ion and the biological coordination agent, the role of manganese ion in the active sites and the structure of the active sites in the manganese enzymes, small molecule complexes are often applied to modeling the structure and the properties of reaction in the active centers (Shi et al.2000). Metal complexes containing monocarboxylic acids are well known and the publication of many structurally characterized examples of this class of compounds has demonstrated the versatility of the carboxylate group as an innersphere ligand (Mehrotra et al., 1983). In this paper, we will report the synthesis and crystal structure of a new two-dimensional manganese complex, [Mn 2 .(dinitrobenzoic acid) 4 .(4,4-bipy) 2 ]n,(I). The crystal structure was confirmeded by X-ray crystallography.
The crystal structure of the title compound is illustrated in Fig.1. The Mn atom is located in an octahedral enviroment containing two N from two bipy ligand, four O from two chelating carboxyl. The Mn-O bond lengths are in the range 2.1281 (13) -2.2011 (12) Å, and the Mn-N bond lengths are 2.269 (2) and 2.278 (2) Å.
Along the a axis, each Mn(II) center is double-bridged by two pair of bi-monodentate carboxyl, and forming a doublestranded chain. Along the b axis, the bidentate ligand 4,4'-bipyridine bridge the Mn atom in a straight mode. As a result, the whole molecule features a two-dimensional structure constructed of oblong grids with the side length 11.634 and 5.075 Å, as shown in Fig.2.

Experimental
The reaction of dinitrobenzoic acid 0.636 g(3 mmol) and NaOH 0.12 g(3 mmol) in the molar ratio of 1:1 in an aqueous-alcohol(3:1) solution(40 ml) at room temperature for 30 minutes produced a colorless solution, to which MnCl 2 .6H 2 O 0.198 g(1 mmol) and 4,4'-bipyridine 0.156 g(1 mmol) was added to produced a yellowy solution. The reaction solution was kept at room temperature after stirring for an hour. Yellowy crystals were obtained after a few days, which were washed with water and ethanol for several times and then dried in air. Fig. 1. A view of the structure of the title compound, showing 30% probability displacement ellipsoids. H atoms have been omitted for clarity. Symmetry codes: (A) -x+1/2, y, -z+1/2; (B) -x+3/2, y, -z+1/2; (C) x, y+1, z;(D) x, y-1, z. Only the carboxyl group of the benzoic acid is shown for clarity.