Bis(μ-pyridinium-2-carboxylato-κ2 O:O′)bis[triaqua(sulfato-κO)manganese(II)]

The asymmetric unit of the title compound, [Mn2(SO4)2(C6H5NO2)2(H2O)6], comprises half of a centrosymmetric dimer. The MnII atom is coordinated by two O atoms of the monodentate carboxylate ligand, an O atom of the sulfate anion in axial position and three water molecules in a distorted octahedral geometry. In the crystal, molecules are connected through N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network. The crystal structure is further stabilized by intermolecular π–π interactions [centroid–centroid distance = 3.842 (2) Å].


Related literature
For standard bond lengths, see: Allen et al. (1987). For background to the applications of Mn II complexes, see: Lee et al. (2004); Mautner et al. (1997).

Comment
As a part of a synthetic work on synthesis and characterization and applications (Lee et al., 2004;Mautner et al., 1997), of new Mn(II) complexes with aromatic carboxylic acid, we determined the X-ray structure of the title compound.
The molecule structure of the title compound ( Fig. 1) is composed of a centerosymmetric dimer of a Mn(II) complex with pyridine-2-carboxylic acid. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The geometry around the Mn II is a distorted octahedron which is coordinated by two oxygen atoms of the carboxylic ligand, an oxygen atom of the sulfate anion, and three oxygen atoms of the coordinated water molecules. Intermolecular N-H···O and O-H···O hydrogen bonds (Table 1), link neighboring molecules, forming three dimensional network (Fig. 2). The crystal structure is further stabilized by the intermolecular π-π interaction [Cg1···Cg1 i = 3.842 (2) Å, (i) 3/2 -x, -1/2 + y, z; Cg1 is the centroid of the (N1/C1-C5) ring.

Experimental
The title compound was synthesized by adding 10 ml solution of pyridine-2-carboxylic acid (1.456 g, 11.832 mmol) to a 10 ml solution of manganese sulfate (2g, 11.832 mmol). The mixture was stirred for 24 h. Light-brown single crystals of the title compound suitable for X-ray structure determination were obtained by slow evaporation of the solvents at room temperature after 4 days.

Refinement
All hydrogen atoms of C were positioned geometrically with C-H = 0.93 Å and included in a riding model approximation with U iso (H) = 1.2 U eq (C). The N-bound H atom was located in a difference Fourier map and constrained to refine with the parent atom by U iso (H) = 1.2 U eq (N). The hydrogen atoms of the water molecules were located in a difference Fourier map and constrained to refine with the parent atoms by U iso (H) = 1.5 U eq (O). Fig. 1. The molecular structure of the title compound, with 40% probability displacement ellipsoids. Symmetry code for the unlabeled atoms: -x + 2, -y + 1, -z + 1 supplementary materials sup-2

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.