Poly[[[μ3-5-(pyridine-4-carboxamido)isophthalato]{μ3-5-[(pyridin-1-ium-4-yl)carbonylamino]isophthalato}neodymium(III)] dihydrate]

In the title compound, {[Nd(C14H9N2O5)(C14H8N2O5)]·2H2O}n, the NdIII atom is eight-coordinated as it is surrounded by eight carboxylate O atoms from six ligands in a distorted square-antiprismatic arrangement. The NdIII atoms are linked by HL − and L 2− ligands [H2 L is 5-(pyridine-4-carboxamido)isophthalic acid], forming a bilayer network. The layers are linked into a three-demensional network through N—H⋯O and O—H⋯O hydrogen bonds.

In the title compound, {[Nd(C 14 H 9 N 2 O 5 )(C 14 H 8 N 2 O 5 )]Á-2H 2 O} n , the Nd III atom is eight-coordinated as it is surrounded by eight carboxylate O atoms from six ligands in a distorted square-antiprismatic arrangement. The Nd III atoms are linked by HL À and L 2À ligands [H 2 L is 5-(pyridine-4-carboxamido)isophthalic acid], forming a bilayer network. The layers are linked into a three-demensional network through N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds.
Poly [[[ 3 -5-(pyridine-4-carboxamido) In recent years, there has a great deal of interest in synthesizing transition metal complexes that exhibit one-, two-and three-dimensional frameworks (Kitagawa & Kondo, 1998). However, high-dimensional lanthanide frameworks are less common (Kiritsis et al., 1998;Zhao et al., 2004). On the other hand, it is well known that carboxylate and pyridine groups have good coordination capacities as well as the amide group, a group with two different types of hydrogen bonding sites: the -NH moiety that acts as an electron acceptor and a -C=O group that acts as an electron donor (Lee, & Kumler, 1962;Huyskens, 1977;Wang et al., 2007). The study reports a new lanthanide(III) coordination polymer, [Nd(HL)(L)] n .2nH 2 O, (I), with H 2 L and Nd(NO 3 ) 3 .6H 2 O.
In the title compound, the central Nd III ion is eight-coordinated by eight O atoms from six ligands, which gives a square antiprismatic geometry (Fig. 1). The carboxyl groups of the two unique L 2-(HL -) ligands exhibit the same coordination modes: there is a monocarboxylate and a dicarboxylate, i.e., the monocarboxylate group coordinates to one Nd III atom in µ 1 -η 1 :η 1 -chelate mode and the other dicarboxylate connects two Nd III atoms in a µ 2 -η 1 :η 1 bridging mode. The pyridyl groups are free. Based on the coordination modes of the carboxylate groups of L 2-(HL -), a bilayer network is formed (Fig.   2). Adjacent molecules are linked through N-H···O and O-H···O hydrogen bonds into a three-dimensional network.

Experimental
A mixture of 0.05 mmol Nd(NO 3 ) 3 .6H 2 O (21.5 mg. 0.05 mmol), H 2 L (28.6 mg, 0.1 mmol), NaOH (6.0 mg, 0.15 mmol), MeOH (4 ml) and H 2 O (6 ml) was heated in a 16 ml Teflon-lined reaction vessel at 453 K for 5 days; the mixture was cooled to room temperature over a period of 40 h. The product was collected by filtration, washed with H 2 O and air-dried.

Refinement
H atoms bonded to C atoms were placed geometrically and refiined as riding atoms. The pyridyl (N1) was found from a difference Fourier maps and refined as riding, with N-H = 0.86 Å, and the water H atoms were found from Fourier difference maps and refined with restraints for O-H distances (0.85 Å) with U iso (H) = 1.2U eq (O). The highest residual electron density was found at 0.07 Å from Nd1 atom and the deepest hole at 0.56 Å from the O1W atom.
Crystal data [Nd(C 14