Lanthanide coordination frameworks: crystal structure, down- and up-conversion luminescence and white light emission

Abstract

Lanthanide–organic frameworks (LnOFs), [Sm(H₂N-BDS)_0.5(ox)(phen)] (1) and [Ln(H₂N-BDS)(ox)_0.5(phen)₂] (Ln = Eu 2, Gd 3, Tb 4, Er 5, Yb 6; H₂N-BDS = 2-amino-1,4-benzenedisulfonate, ox = oxalate, and phen = 1,10-phenanthroline) were obtained using hydrothermal synthesis. Structural analyses revealed that 1 is a three-dimensional (3D) pillared-layer structure constructed from [SmO₆N₂] polyhedra, and tetradentate H₂N-BDS and tetradentate ox ligands, while complexes 2–6 are isostructural 2D frameworks, constructed from [LnO₄N₄] polyhedra, and bidentate H₂N-BDS and tetradentate ox ligands. The LnOFs containing Sm(III), Eu(III) and Tb(III) ions exhibited the characteristic down-conversion luminescence of the corresponding Ln(III) ions. The Gd:Tb,Eu doped complex provided a white light emission. The Gd:Yb,Er doped complex exhibited up-conversion emissions at 410 nm (⁴H_9/2 → ⁴I_15/2, blue), 518–570 nm (⁴S_3/2, ²H_11/2 → ⁴I_15/2, green), and 655 nm (⁴F_9/2 → ⁴I_15/2, red).