Surface-grafted lanthanoid complexes of the tungstosilicate polyanion [SiW 12 O 40 ] 4- : a synthetic, structural and computational investigation.

As an extension of our continued interest in the preparation of inorganic-organic hybrids, we report the successful hydrothermal synthesis of sodium tris[triaqua(μ-1,10-phenanthroline-2,9-dicarboxylato)dysprosium(III)] silicododecatungstate dodecahydrate, {[DyNa(C14 H6 N2 O4 )3 (H2 O)9 (SiW12 O40 )]·12H2 O}n or Na[Dy(PDA)(H2 O)3 ]3 [SiW12 O40 ]·12H2 O (1), and sodium aqua tris[tetraaqua(μ-4-hydroxypyridine-2,6-dicarboxylato)praseodymium(III)] silicododecatungstate dodecahydrate, {[NaPr(C7 H3 NO5 )3 (H2 O)13 (SiW12 O40 )]·12H2 O}n or Na(H2 O)[Pr(pydc-OH)(H2 O)4 ]3 [SiW12 O40 ]·12H2 O (2) (in which H2 PDA is 1,10-phenanthroline-2,9-dicarboxylic acid and H2 pydc-OH is 4-hydroxypyridine-2,6-dicarboxylic acid or chelidamic acid). Both compounds have been characterized using elemental analysis, IR spectroscopy and X-ray diffraction methods. Structural characterization by single-crystal X-ray diffraction reveals that these compounds consist of [SiW12 O40 ]4- Keggin-type polyoxometalates (POMs), where a single {W3 O13 } triad is decorated with a trinuclear Ln complex. Moreover, the decorated polyanions are involved in a series of intermolecular interactions, such as hydrogen bonds and anion-π interactions, resulting in three-dimensional supramolecular architectures. Density functional theory (DFT) studies were conducted to support these intermolecular interactions in both 1 and 2, and have been rationalized using molecular electrostatic potential (MEP) surface calculations.