Crystal structure of poly[[μ3-4,4′-(4,4′-bipyridine-2,6-diyl)dibenzoato]{μ2-4-[6-(4-carboxyphenyl)-4,4′-bipyridin-4′-ium-2-yl]benzoato}manganese(II)] hemihydrate]

The title compound, {[Mn(C24H14N2O4)(C24H16N2O4)]·0.5H2O}n, was obtained by the reaction of manganese nitrate with the ligand 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid under hydrothermal conditions. The water O atom is located on a twofold rotation axis. The Mn2+ ion is heptacoordinated by six O atoms and one N atom from the ligands. In this structure, the ligands adopts two different forms, one completely deprotonated and one with a protonated N atom (pyridinium) and a carboxylic acid function. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds consolidate the packing, forming a three-dimensional framework.


S2. Refinement
All the hydrogen atoms attached to carbon atoms were placed in calculated positions and refined using a riding model.
The hydrogen atoms of the protonated carboxylic group and protonated nitrogen atom were located from the Fourier difference map. They were refined isotropically with the O-H and N-H distance restrained to 0.89 (2)Å. The water H atom was refined using a riding model.

S3. Comment
In recent years, much attention has been paid to coordination polymers that have shown perspective in the field of gas adsorption and separation and molecular recognition. Particularly, 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid was used to form various metal-organic coordination polymers with novel structures (Hou et al., 2010;Sharma et al., 2011;Song et al., 2012, Wei et al. 2013. We report here the synthesis and the crystal structure of the title coordination polymer. In the asymmetric unit, there are one crystallographically independent Mn(II) ion, two ligands with different degrees of deprotonation and half a water molecule. The Mn 2+ ion is heptacoordinated by six O atoms and one nitrogen atom from the ligands (Figure 1). The carboxylate groups of the completely deprotonated L 2anion adopt chelating modes, and the nitrogen atom coordinates to the Mn(II) ion; In the other form of the ligand, both the deprotonated carboxylate group and the protonated carboxylic group adopt the monodentate mode, and the nitrogen atom of the terminal pyridyl ring is protonized, not coordinated to the Mn(II) ion. This compound manifests a three-dimensional framework, with versatile hydrogen bonding consolidating the crystal packing ( Figure 2).

Figure 2
View of the three-dimensional framework of the titled compound. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.005 Δρ max = 0.43 e Å −3 Δρ min = −0.73 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
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