Two GdIII complexes with different structures and magnetocaloric properties induced by metal ion sources

Abstract

Two new Gd^III complexes with the formulas of [Gd(ma)₂(H₂O)₂]·2H₂O (1) and {[Gd(ma)(ox)_0.5(H₂O)]·2H₂O}_n (2) (H₂ma = DL-malic acid and H₂ox = oxalic acid) have been successfully prepared by using Gd₂O₃ or Gd(NO₃)₃ as metal ion sources. Complex 1 exhibits a discrete mononuclear structure, while complex 2 displays a three-dimensional ‘layer-pillar’ structure with ox²⁻ anions as pillars that are generated in situ. Magnetic studies suggest the presence of ferromagnetic couplings between the intramolecular or interlayer Gd^III ions and large magnetocaloric effects with −ΔS^max_m = 32.1 J kg⁻¹ K⁻¹ (1) and 44.6 J kg⁻¹ K⁻¹ (2) for ΔH = 7 T. Therefore, they are good candidates as magnetic refrigerants.