Urothermal synthesis of mononuclear lanthanide compounds: slow magnetization relaxation observed in Dy analogue

Abstract

Two mononuclear compounds Ln(e-urea)₈(NO₃)₃ (Ln = Dy(1) and Tb(2)) have been urothermally synthesized by using the ethyleneurea (e-urea) as an organic ligand and a solvent. The e-urea ligand with a single donor atom is a unique ligand for coordinating to lanthanide ions, which is very different from those commonly observed polytopic ligands with suitable coordination pockets to encapsulate lanthanide(III) ions or chelating organic ligands. The lanthanide center surrounded by eight e-urea ligands is in a square antiprismatic environment with an approximate D_4d local symmetry. Magnetic properties of both compounds have been investigated in detail using direct-current and alternating-current susceptibility measurements. The Dy(1) analogue displays slow magnetic relaxation behavior with an effective energy barrier of the magnetic relaxation of 37.68 K and the pre-exponential factor τ₀ of 1.47 × 10⁻⁹ s in the presence of direct-current field of 2 kOe.