Syntheses, structures and photophysical properties of Zn–Ln coordination polymers

Eight novel coordination polymers, {[LnZn(2,3-pydc)2(ox)0.5(H2O)3]·3H2O}n (Ln = Pr 1, Nd 2, Ho 3, Er 4, Yb 5, Sm 6, Eu 7, Tb 8) (2,3-H2pydc = pyridine-2,3-dicarboxylic acid, H2ox = oxalic acid) are synthesized by the hydrothermal method and their structures are determined by single-crystal X-ray diffraction. They are isomorphous and crystallized in the triclinic system, with space group P1¯. In crystals, Ln(III) and Zn(II) ions are linked into 2D layers by 2,3-pydc2− ligands adopting two coordination modes, and neighboring layers are bridged into 3D network structure through oxalate ligands in bridging tetradentate coordination mode. The IR, UV–Vis–NIR absorption spectra and emission spectra in the visible and near-infrared (NIR) region of polymers are determined and analyzed. All of polymers exhibit characteristic emission bands of corresponding Ln(III) ions, which should be attributed to sensitization from the d-block (Zn–ligand moiety) and ligands after introducing Zn(II) ion into the system of Ln(III) complexes.

Graphical abstractEight 3D heterometallic Zn–Ln coordination polymers have been hydrothermally synthesized and exhibit characteristic emissions of Ln(III) ions in the visible region or NIR region owing to sensitization from d-block and ligands after forming Zn–Ln polymers.Figure optionsDownload full-size imageDownload as PowerPoint slide