Structures, luminescent and magnetic properties of six lanthanide–organic frameworks: observation of slow magnetic relaxation behavior in the DyIII compound

Abstract

Six novel three-dimensional (3D) lanthanide metal–organic frameworks (LnMOFs), {[Ln₂(ispc)₃(H₂O)₃]·mH₂O}_n (Ln = Pr (1, m = 5); Eu (2, m = 5); Gd (3, m = 4); Tb (4, m = 5); Dy (5, m = 5) and Ho (6, m = 4)), ispc = 3-(4-carboxyphenylsulfonyloxy)-4-methoxybenzoic anion) have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction revealed they are isostructural and crystallize in the triclinic crystal system, space group P. The investigations on luminescent properties and lifetimes of 2 (Eu^III), 4 (Tb^III), and 5 (Dy^III) exhibit characteristic emissions of Eu^III, Tb^III and Dy^III ions and the corresponding luminescent lifetimes are 0.14 ms, 9.93 μs and 1.25 ms, respectively. The different luminescent intensities and lifetimes among them were further discussed. Furthermore, magnetic studies of 1–6 reveal that 3–6 exhibit ferromagnetic coupling, and 5 (Dy^III) exhibits remarkably slow magnetic relaxation behavior with the energy barrier ΔE/k_B = 49.2 K.