Structures, luminescent and magnetic properties of six lanthanide-organic frameworks: observation of slow magnetic relaxation behavior in the Dy-III compound

Six novel three-dimensional (3D) lanthanide metal-organic frameworks (LnMOFs), {[Ln(2)(ispc)(3)(H2O)(3)]center dot mH(2)O}(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 (1) over bar. 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 mu s 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 Delta E/k(B) = 49.2 K.