Two hexanuclear 3d–4f cluster complexes containing the pyridine-2-aldoximate ligand (pao⁻), [Ni₂Ln₄ (hfac)₈(pao)₆(CH₃COO)₂(MeOH)]·H₂O·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.