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

A heteroditopic ligand (HL1) containing picolinate and benzoate moieties segmented by a triple bond has been used in the preparation of a family of isostructural coordination polymers of the formula [(CH)NH][Ln((HO)L1)] (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 2/ 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 slow relaxation of magnetization (SRM) under an applied DC magnetic field. On the other hand, Tb (3) and Ho (5) compounds, based on non-Kramers ions, lack SRM properties. Compound 2 is one of the few reported Gd(III) compounds showing slow relaxation behaviour.