Octanuclear {Ln 8 } complexes: magneto-caloric effect in the {Gd 8 } analogue

Two neutral, isostructural, octanuclear, Ln III complexes, [Ln 8 (HL) 6 (L) 2 ( μ 3 -OH) 4 ( μ 2 -OH) 2 (H 2 O) 4 ].solv (Ln = Gd(III), ( 1 Gd ) and Dy(III), ( 2 Dy ) have been synthesized using Ln III nitrate salts and a o -vanillin-supported multi-dentate ligand, N' -(2-hydroxy-3-methoxy-5-nitrobenzylidene)-2-(hydroxyamino) propanehydrazide (H 3 L) in the presence of tetramethyl ammonium hydroxide. The complexes were structurally characterized by single crystal X-ray diffraction studies. The complexes are held by the cumulative coordination action of six [HL] 2− , two [L] 3− chelating ligands, H 2 O and hydroxide ligands. Magneto-structural analysis of complexes 1 Gd and 2 Dy reveals the presence of intramolecular antiferromagnetic interactions between the Ln III ions. Magneto-caloric effect was analysed for the complex 1 Gd which shows a maximum in the change of molar entropy (–Δ S m ) of magnitude 25.5 J kg –1 K –1 at T = 3 K and an applied field change Δ B = 5 T. Graphical abstract