Synthesis, structure and slow magnetic relaxation of lanthanoid coordination polymers based on ethynyl-bridged picolinate ligands

Abstract

A heteroditopic ligand (H₂L₁) containing picolinate and benzoate moieties segmented by a triple bond has been used in the preparation of a family of isostructural coordination polymers of formula [(CH₃)₂NH₂][Ln((H₂O)₂L₁)₂] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5) and Er (6)). The single crystal structures show that these compounds crystallize in the monoclinic I2/a space group and form anionic layers with rhomboidal voids. AC magnetic susceptibility measurements show that compounds based on Kramers ions, such as the Gd (2), Dy (4) and Er (6) derivatives, present a slow relaxation of the magnetization (SRM) under an applied DC magnetic field. Instead, Tb (3) and Ho (5) compounds, based on non-Kramers ions, lack of SRM properties. Compound 2 is one of the few reported Gd(III) compounds showing slow relaxation behaviour.