Poly[[diaquatris(μ2-3-methylpyridine-2-carboxylato)(3-methylpyridine-2-carboxylato)sodiumterbium(III)] ethanol monosolvate monohydrate]

In the title compound, {[NaTb(C7H6NO2)4(H2O)2]·C2H5OH·H2O}n, the TbIII atom is eight-coordinated in a slightly distorted square-antiprismatic geometry defined by four carboxylate O atoms and four pyridine N atoms. The bond lengths lie within the range 2.3000 (2)–2.326 (2) Å for the Tb—O bonds and 2.543 (3)–2.553 (3) Å for the Tb—N bonds. The NaI atom is five-coordinated by two water O atoms and three carboxylate O atoms in a distorted square-pyramidal geometry. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into a three-dimensional network.

In the title compound, {[NaTb(C 7 H 6 NO 2 ) 4 (H 2 O) 2 ]ÁC 2 H 5 OHÁ-H 2 O} n , the Tb III atom is eight-coordinated in a slightly distorted square-antiprismatic geometry defined by four carboxylate O atoms and four pyridine N atoms. The bond lengths lie within the range 2.3000 (2)-2.326 (2) Å for the Tb-O bonds and 2.543 (3)-2.553 (3) Å for the Tb-N bonds. The Na I atom is five-coordinated by two water O atoms and three carboxylate O atoms in a distorted square-pyramidal geometry. In the crystal, intermolecular O-HÁ Á ÁO hydrogen bonds link the molecules into a three-dimensional network.
In the title compound, {[NaTb(H 2 O) 2 (C 7 H 6 NO 2 ) 4 ].C 2 H 5 OH.H 2 O} n , the Tb III atom is eight-coordinated within a slightly distorted square antiprismatic geometry. The Tb III atom is coordinated to the four carboxylate-O atoms and four pyridine-N atoms. The Tb-O bond distances are within the range of 2.300 (2)-2.326 (2) Å (Table 1), which are significantly shorter than the sum of the covalent radii of Tb and O atoms (2.420 Å). The Na + ion is five-coordinated with two water-O atoms and three carboxylate-O atoms to form a distorted square pyramidal geometry. In the crystal structure, intermolecular O-H···O hydrogen bonds (Table 2) link the uncoordinated water molecule to the coordinated picolinic ligands and further link the molecules into a three-dimensional network.
The title compound exhibits an intense emission at 543 nm upon 326 nm excitation in PL spectra with 325 nm of He-Cd laser excitation wavelength

Experimental
Terbium trichloride solution was prepared by dissolving TbCl 3 .6H 2 O (0.27 g, 1.0 mmol; Aldrich) in absolute ethanol (20 ml) at room temperature with stirring. The ligand solution was prepared by dissolving 3-methylpicolinic acid (0.55 g, 4.0 mmol; Aldrich) in absolute ethanol (30 ml) at room temperature with stirring. The pH of the ligand solution was adjusted to about 5.1 with 2 N NaOH solution. The Terbium trichloride solution was added dropwise slowly to the ligand solution. The reaction mixture was stirred for 1 h at room temperature. Colourless crystals of (I) were obtained at room temperature over a period of a few weeks. The complex was recrystallized from the mixture of distilled water and absolute ethanol solution.

Refinement
The O-H atoms were located in a difference Fourier map and refined with O-H = 0.81±0.01 Å. The remaining H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.97 Å, and with U iso (H) = 1.2U eq (C) for aromatic and methylene-H and 1.5U eq (C) for methyl-H atoms. The maximum and minimum residual electron density peaks of 0.51 and -0.56 e Å -3 , respectively, were located 0.85 Å and 0.57 Å from the Tb1 atom, respectively.