Reactions of Ln(III) perchlorate (Ln = Gd, Tb, Dy, and Ho), NiCl2 center dot 6H(2)O, and a polydentate Schiff base resulted in the assembly of novel isostructural hexanuclear Ni(4)Ln(2) complexes [Ln = Gd (1), Tb (2), Dy (3), Ho (4)] with an unprecedented 3d-4f metal topology consisting of two defect-dicubane units. The corresponding Ni4Y2 (5) complex containing diamagnetic Y-III atoms was also isolated to assist the magnetic studies. Interestingly, complexes 2 and 3 exhibit SMM characteristics and 4 shows slow relaxation of the magnetization. The absence of frequency-dependent in-phase and out-of-phase signals for the Ni-Y species suggests that the Ln ions' contribution to the slow relaxation must be effectual as previously observed in other Ni-Dy samples. However, the observation of chi '' signals with zero dc field for the Ni-Tb and Ni-Ho derivatives is notable. Indeed, this is the first time that such a behavior is observed in the Ni-Tb and Ni-Ho complexes.