catena-Poly[[[tetraaqualanthanum(III)]-di-μ-isonicotinato-κ4 O:O′] chloride]

In the title compound, {[La(C6H4NO2)2(H2O)4]Cl}n, the LaIII atom lies on a twofold rotation axis and is eight-coordinated by four O atoms from four isonicotinate ligands and four water molecules in a distorted square-antiprismatic coodination environment. Adjacent LaIII atoms are bridged by two carboxylate groups from two isonicotinate ligands, forming an extended chain along [001]. These chains are linked through O—H⋯N hydrogen bonds into a three-dimensional network with channels in which the chloride anions form O—H⋯Cl hydrogen bonds. Intrachain O—H⋯O hydrogen bonds and π–π interactions [centroid–centroid distance = 3.908 (2) Å] are also observed.

In the title compound, {[La(C 6 H 4 NO 2 ) 2 (H 2 O) 4 ]Cl} n , the La III atom lies on a twofold rotation axis and is eight-coordinated by four O atoms from four isonicotinate ligands and four water molecules in a distorted square-antiprismatic coodination environment. Adjacent La III atoms are bridged by two carboxylate groups from two isonicotinate ligands, forming an extended chain along [001]. These chains are linked through O-HÁ Á ÁN hydrogen bonds into a three-dimensional network with channels in which the chloride anions form O-HÁ Á ÁCl hydrogen bonds. Intrachain O-HÁ Á ÁO hydrogen bonds and interactions [centroid-centroid distance = 3.908 (2) Å ] are also observed.

Jin-He Zhao Comment
Much attention has been devoted to the research on lanthanide metal polynuclear compounds because of their magnetic and luminescent properties. Most of these types of compounds were synthesized by the reaction of rare-earth metal ions with bi-or multi-dentate ligands such as nicotinic acid (Kay et al., 1972;Ma, Hu et al., 1996;Starynowicz, 1991Starynowicz, , 1993, isonicotinic acid (Chen & Fukuzumi, 2009;Ma, Evans et al., 1999;Wu et al., 2008;Zeng et al., 2000) and isonicotinic acid N-oxide (Mao et al., 1998). In the course of research in this area, our extended group has reported several such compounds with different bridging ligands (Cai et al., 2003;Cui et al., 1999;Zhang et al., 1999). Herein, we report the synthesis and crystal structure of a new lanthanum complex with isonicotinic ligand.  (Mao et al., 1998) and [La(C 6 H 4 NO 2 ) 2 (H 2 O) 4 ](NO 3 ) (Cai et al., 2003), but differs from those found in Ln(isonicotinate) 3 (H 2 O) 2 (Ln = Ce, Pr, Nd, Sm, Eu, Tb) (Ma, Evans et al., 1999), in which the Ln III atoms are bridged by four syn-syn µ-O:O′-carboxylate groups of the isonicotinic ligands (Ln = Ce, Pr, Nd) or coordinated by both two syn-syn µ-O:O′-carboxylate groups and chelating carboxylate groups of the isonicotinic ligands (Ln = Sm, Eu, Tb). To the best of our knowledge, the arrangement in the present complex is rare in the lanthanide analogs.
There are three kinds of hydrogen bonds, O-H···Cl, O-H···O and O-H···N (Table 1). Interchain O-H···N hydrogen bonds between the coordinated water molecules and uncoordinated N atoms of the isonicotinate ligands link the cationic chains into a three-dimensional network with channels along [0 0 1], in which the chloride anions are located, as shown in Fig. 2, forming O-H···Cl hydrogen bonds. Intrachain O-H···O hydrogen bonds are also present. π-π stacking interactions exist between two adjacent isonicotinate ligands located in a same chain [centroid-centroid distance = 3.908 (2) Å].

Experimental
LaCl 3 .7H 2 O (0.3174 g, 1 mmol), isonicotinic acid (0.2442 g, 2 mmol), NaOH (0.08 g, 2 mmol) were added to a mixture of water (15 ml) and ethanol (10 ml). The resulting mixture was stirred at 423 K for 4 h and filtered off. The filtrate was allowed to stand at room temperature and slow evaporation afforded colorless block crystals of the title complex (yield: 65%

Refinement
H atoms on C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C). The water H atoms were located in difference Fourier maps and refined using a riding model, with O-H = 0.85 Å and U iso (H) = 1.2U eq (O). program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  Packing diagram of the title compound. Yellow dashed lines represent π-π interactions and green dashed lines represent hydrogen bonds. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.46 e Å −3 Δρ min = −0.83 e Å −3 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.