Poly[diaqua-μ2-isonicotinato-μ2-oxalato-terbium(III)]

In the crystal structure of the title complex, [Tb(C6H4NO2)(C2O4)(H2O)2]n, the TbIII cation is coordinated by four O atoms from two oxalate ligands, two O atoms from two isonicotinate ligands and two O atoms from water molecules within a distorted square–antiprismatic coordination. The TbIII cation, the isonicotinate anion and the two crystallographically independent water molecules occupy general positions, whereas one of the two crystallographically independent oxalate anions is located on a center of inversion, and the second oxalate anion is located on a twofold rotation axis. The TbIII cations are linked by the oxalate and isonicotinate anions into layers, which are connected via intermolecular hydrogen-bonding and π–π stacking [with centroid-to-centroid distances of 3.509 (2) and 3.343 (3) Å] interactions into a three-dimensional network.

In the crystal structure of the title complex, [Tb(C 6 H 4 NO 2 )-(C 2 O 4 )(H 2 O) 2 ] n , the Tb III cation is coordinated by four O atoms from two oxalate ligands, two O atoms from two isonicotinate ligands and two O atoms from water molecules within a distorted square-antiprismatic coordination. The Tb III cation, the isonicotinate anion and the two crystallographically independent water molecules occupy general positions, whereas one of the two crystallographically independent oxalate anions is located on a center of inversion, and the second oxalate anion is located on a twofold rotation axis. The Tb III cations are linked by the oxalate and isonicotinate anions into layers, which are connected via intermolecular hydrogen-bonding andstacking [with centroid-to-centroid distances of 3.509 (2) and 3.343 (3) Å ] interactions into a three-dimensional network.

Poly[diaqua-µ 2 -isonicotinato-µ 2 -oxalato-terbium(III)]
Wen-Dong Song, Shi-Jie Li, Pei-Wen Qin and Shi-Wei Hu S1. Comment The use of multifunctional organic linker molecules in the preparation of coordination polymers and open-framework materials has led to the development of a rich field of chemistry (Yaghi et al., 1998(Yaghi et al., , 2003Serre et al., 2004;James, 2003) owing to the potential applications of these materials in catalysis, separation, gas storage and molecular recognition. In our own investigatins we used isonictinate and oxalate ligands for the preparation of new coordination polymers, because it has been found that both anions can act as multidentate ligands [Xia et al. (2004); Feng et al. (2003)] with versatile binding and coordination modes. During these investigations, single crystals of the title compound were obtained.
The Tb III centre in the title compound exhibits a distorted square-antiprismatic coordination geometry, defined by eight O atoms from two oxalate ligands, two O atom from two isonictinate ligands and two water molecules (Fig. 1). The oxalate and isonictinate ligands link the Tb III cations with Tb-Tb distances of 6.179 (2) Å, 6.183 (3) Å and 5.045 (2) Å, respectively, thus forming Tb-oxalate-isonictinate layers with the attached water that is pointing up and down (Fig. 2).
The layers are connected into a three-dimensional network via inter/intramolecular O-H···O and O-H···N hydrogen bonding interactions (Table 1) involving the coordinated water molecules, the N atoms of isonictinate and the oxalate O atoms. They are also stabilized by π-π stacking interactions with centroid to centroid distances of 3.509 (2) Å and 3.343 (3) Å, respectively, among parellel pyridinium rings of neighboring complexes.

S2. Experimental
A mixture of Tb 2 O 3 (0.5 mmol, 0.175 g), sodium oxalate (1 mmol, 0.134 g), isonicotinic acid (1 mmol, 0.123 g) and H 2 O (10 ml) was placed in a 23 ml Teflon reactor, which was heated to 433 K for three days and then cooled to room temperature at a rate of 10 K h -1 . The crystals obtained were washed with water and dryed in air.  The structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 30% probability level. [Symmetry codes: (i) 1 -x, y, 0.5 -z; (ii) 0.5 -x, 2.5 -y, -z; (iii) 0.5 -x, 1.5 -y, -z]

Figure 2
Crystal structure of the title compound with view onto the layers. The H atoms are not shown for clarity.

Poly[diaqua-µ 2 -isonicotinato-µ 2 -oxalato-terbium(III)]
Crystal data 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.