Isostructural lanthanide metal-organic frameworks comprised of left-handed helical chains: Synthesis, structure and luminescent properties

摘要

Six isostructural three-dimensional (3D) lanthanide metal-organic frameworks (Ln-MOFs), [Ln(mu(2)-OH)(PDC) (H2O)(2)]center dot DMF (Ln = Pr (1), Nd (2), Eu (3), Tb (4), Ho (5), and Yb (6), H2PDC = pyridine-3,5-dicarboxylic acid), have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal gravimetric analysis. The framework contains unusual Ln-carboxylate/mu(2)-OH left-handed helical chains, which are extended by PDC2- linkers to form 3D networks with 1D hexagonal channel. The lanthanide contraction effect induces the decreases of average Ln-distances from Pr to Yb. Due to the efficient sensitization of PDC2- ligand, complexes 2 and 6 display strong characteristic luminescence in the near-infrared (NIR) region, respectively. Moreover, the luminescent properties of complexes 3 and 4 are also studied in the solid state at room temperature. (C) 2018 Elsevier B.V. All rights reserved.