A Series of Three-Dimensional Lanthanide Coordination Polymers with Rutile and Unprecedented Rutile-Related Topologies

The complexes of formulas Ln(pydc)(Hpydc) (Ln = Sm (<b>1</b>), Eu (<b>2</b>), Gd (<b>3</b>); H<sub>2</sub>pydc = pyridine-2,5-dicarboxylic acid) and Ln(pydc)(bc)(H<sub>2</sub>O) (Ln = Sm (<b>4</b>), Gd (<b>5</b>); Hbc = benzenecarboxylic acid) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, TG analysis, and single-crystal X-ray diffraction. Compounds <b>1</b><b>−</b><b>3</b> are isomorphous and crystallize in the orthorhombic system, space group <i>Pbcn</i>. Their final three-dimensional racemic frameworks can be considered as being constructed by helix-linked scalelike sheets. Compounds <b>4</b> and <b>5</b> are isostructural and crystallize in the monoclinic system, space group <i>P</i>2<sub>1</sub>/<i>c</i>. pydc ligands bridge dinuclear lanthanide centers to form the three-dimensional frameworks featuring hexagonal channels along the <i>a</i>-axis that are occupied by one-end-coordinated bc ligands. From the topological point of view, the five three-dimensional nets are binodal with six- and three-connected nodes, the former of which exhibit a rutile-related (4.6<sup>2</sup>)<sub>2</sub>(4<sup>2</sup>·6<sup>9</sup>·8<sup>4</sup>) topology that is unprecedented within coordination frames, and the latter two species display a distorted rutile (4.6<sup>2</sup>)<sub>2</sub>(4<sup>2</sup>·6<sup>10</sup>·8<sup>3</sup>) topology. Furthermore, the luminescent properties of <b>2</b> were studied.