catena-Poly[[[tetraaquaneodymium(III)]-di-μ-isonicotinato] chloride]

In the title complex, {[Nd(C6H4NO2)2(H2O)4]Cl}n, the NdIII cation is located on a twofold rotation axis and coordinated by four isonicotiniate anions and four water molecules in a distorted square-antiprismatic geometry. The carboxylate groups of the isonicotinate anions bridge the NdIII cations, forming polymeric chains running along the c axis. The Cl− anion is located on a twofold rotation axis and is linked to the polymeric chains via O—H⋯Cl hydrogen bonding. Intermolecular O—H⋯O and O—H⋯N hydrogen bonds are also present in the crystal structure.

In the title complex, {[Nd(C 6 H 4 NO 2 ) 2 (H 2 O) 4 ]Cl} n , the Nd III cation is located on a twofold rotation axis and coordinated by four isonicotiniate anions and four water molecules in a distorted square-antiprismatic geometry. The carboxylate groups of the isonicotinate anions bridge the Nd III cations, forming polymeric chains running along the c axis. The Cl À anion is located on a twofold rotation axis and is linked to the polymeric chains via O-HÁ Á ÁCl hydrogen bonding. Intermolecular O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds are also present in the crystal structure.

Comment
In the synthesis of prepare a lanthanide-isonicotinamide complex, the isonicotinamide changed to isonicotinic acid, resulting in the title complex.
Among aromatic carboxylic acids, isonicotinic acid has a conjugated structural motif and can be used to construct extended structures because it is unsymmetrical divergent ligand. Isonicotinic acid with metal ions may have various coordination modes (Chen et al., 2009). The molecular structure of the title compound is shown in Fig. 1 (Ma et al., 1999); or may coordinate to four carboxylate oxygen atoms of bridging isonicotinate groups, two carboxylate oxygen atoms of the chelating isonicotinate group, and two water molecules (Ma et al., 1999;Han et al., 2010;Kay et al., 1972); or have structure similar to the NdCl-isonicotinic acid complex reported here (Chen et al., 2009). Because Clor NO 3 does not coordinate to lanthanide ions, so Nd(III) chloride or nitrate ion-isonicotinic acid complexes have the similar coordination sphere (Duan et al., 2010;Jia et al., 2008). When oxalate ligands, chromate ions or other ligands are involved, the coordination situations are a little different (Cheng et al., 2007;Liu et al., 2006;Chai et al., 2010) because oxalate ligand, chromate ions or other ligands also coordinate to metal ions.

Experimental
NdCl 3 (1 mmol) and isonicotinamide (3 mmol) were dissolved in 3ml water and 6 ml ethanol. The solution was put on a water bath, temperature was raised to 80°C. Small aliquots of EtOH were periodically added to the solution during the heating process to prolong the reaction time. The resulting mixtures were filtered and left for crystallization in room temperature, the suitable crystals for X-ray diffraction measuraments were obtained in two weeks.

Refinement
The C-bound H-atoms were placed in calculated positions (C-H 0.930 Å) and were included in the refinement in the riding model approximation, U iso (H) = 1.2U eq (C  Fig. 1. The molecular structure of the title compound, displacement ellipsoids drawn at 30% probability level. The Hydrogen atoms have been omitted for clarity.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq