Slow Relaxation of Magnetization and Magnetocaloric Effects in One-Dimensional Oxamato-Based Lanthanide(III) Coordination Polymers

Herein, we present the synthesis and characterization of a series of isostructural lanthanide(III) compounds with the N-(4-carboxyphenyl)oxamic acid (H3pcpa) ligand of the general formula as {[Ln2(Hpcpa)3(H2O)5]}n [Ln = Dy(III) 1, Ho(III) 2, Er(III) 3]. The structure of 3 consists of neutral zig–zag chains of Er(III) ions, with Hpcpa2– ligands acting as bridges in a bidentate/monodentate coordination mode with five water molecules achieving the eight-coordination around the two Er(III) ions within the repeating bis(carboxylate)-bridged dinuclear units along the chain. The magnetic and magnetocaloric properties were studied for 1–3. Compound 1 presents a field-induced slow relaxation of the magnetization with a “reciprocating thermal behavior” below 5 K for H = 0.25 T, while 2 shows maxima of the magnetic entropy from 3 up to 6 K for ΔH > 2 T.