Co(3)Gd(4) Cage as Magnetic Refrigerant and Co(3)Dy(3) Cage Showing Slow Relaxation of Magnetisation

Two structurally dissimilar 3d-4f cages having the formulae [(Co(III))(3)Gd(4)(μ(3)-OH)(2)(CO(3)) (O(2)C(t)Bu)(11)(teaH)(3)]·5H(2)O (1) and [(Co(III))(3)Dy(3)(μ(3)-OH)(4)(O(2)C(t)Bu)(6)(teaH)(3)]·(NO(3))(2)·H(2)O (2) have been isolated under similar reaction conditions and stoichiometry of the reactants. The most important factor for structural diversity seems to be the incorporation of one μ(3)-carbonate anion in 1 and not in 2. Co atoms are in a +3 oxidation state in both complexes, as shown by the Bond Valence Sum (BVS) calculations and bond lengths, and as further supported by magnetic measurements. Co(3)Gd(4) displays a significant magnetocaloric effect (−∆S(m) = 25.67 J kg(−1) K(−1)), and Co(3)Dy(3) shows a single molecule magnet (SMM) behavior.