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

Eight novel coordination polymers, {[LnZn(2,3-pydc)(2)(ox)(0.5)(H2O)(3)]center dot 3H(2)O}(n) (Ln = Pr 1, Nd 2, Ho 3, Er 4, Yb 5, Sm 6, Eu 7, Tb 8) (2,3-H(2)PYdc = pyridine-2,3-dicarboxylic acid, H(2)ox = 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 P (1) over bar. In crystals, Ln(III) and Zn(II) ions are linked into 2D layers by 2,3-pydc(2-) 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. (C) 2015 Elsevier Ltd. All rights reserved.