Hexanuclear [Ni(2)Ln(4)] clusters exhibiting enhanced magnetocaloric effect and slow magnetic relaxation

Two hexanuclear 3d-4f cluster complexes containing the pyridine-2-aldoximate ligand (pao(-)), [Ni(2)Ln(4)(hfac)(8)(pao)(6)(CH3COO)(2)(MeOH)]center dot H2O center dot MeOH (Ln = Gd, 1; Ln = Dy, 2; hfac(-) = hexafluoroacetylacetonate), have been synthesized, which show similar structures with an interesting 'trigonal bipyramid' metal topology. Magnetic determinations revealed that the Ni-Gd species has a spin ground state of 16 due to the dominant ferromagnetic exchange, exhibiting an enhanced magnetocaloric effect, which can be used as a cryogenic magnetic cooler; while the Ni-Dy analogue displays slow magnetic relaxation, a typical characteristic of a single-molecule magnet.