Magnetic properties of 3D lanthanide complexes with 1,3-bis(diphenylphosphoryl)-2-oxapropane: the slow magnetic relaxation of Yb3+ compounds†

For the first time, polymeric isostructural complexes of Y³⁺, Dy³⁺, Yb³⁺ and diamagnetically diluted Dy³⁺ and Yb³⁺ with flexible-chain phosphoryl podand 1,3-bis(diphenylphosphoryl)-2-oxapropane (L) were synthesized and characterized by X-ray, elemental analysis, IR and NMR spectroscopy. The bridging function of the ligand L leads to the formation of a 3D framework. The AC susceptibility measurements of the Dy³⁺ complex with L (1) indicated the absence of slow relaxation of magnetization in magnetic fields up to 5000 Oe. The study of the AC magnetic behavior of the Yb³⁺ complex with L (6) showed the presence of slow magnetic relaxation in the DC field of 2500 Oe with the most probable magnetization reversal path being the combination of Raman mechanism and the direct process. The value of the effective energy barrier of magnetic relaxation ΔE/k_B according to the approximation of the high temperature part of the τ(1/T) plot to the Arrhenius equation is 24 K. Diamagnetic dilution of Dy³⁺ and Yb³⁺ compounds revealed no significant impact on the slow relaxation of magnetization.