The versatility for a unique aggregation of heterometallic 3d-4f and 3d-3d'-4f ions by the new Schiff base ligand 2-{[(2-hydroxy-3-methoxybenzypimino]methyllphenol (H2L) providing O3N donors has been examined. A series of complexes having the general formula [Ln(2)Ni(4)(L)(4)(mu(1,3)-CH3CO2)(2)(mu(3)-OH)(4)(MeOH)(2)]center dot xCH(3)OH center dot yH(2)O [where Ln Dy-III, x = 4, y = 0 (1), Ln = Tb-III, x = 0, y = 4 (2), and Ln = Ho-III, x = 4, y = 0 (3)] were obtained from the sequential use of lanthanide(III) nitrate salts and Ni(CH3CO2)(2)center dot 4H(2)O. The incorporation of two different 3d ions and one 4f ion in the same coordination aggregate was achieved through the isomorphic replacement of two Ni-III centers by Mn-III ions as second group of cationic complexes, [Ln(2)Ni(2)Mn(2)(L)(4)(mu(1,3)-CH3CO2)(2)(mu(3)-OH)(4)(MeOH)(2)]-(NO3)(2)center dot 2CH(3)OH [where Ln = Dy-III (4), Tb-III (5), and Ho-III (6)]. Direct-current (dc) magnetic susceptibility studies hint to the possibility of ferromagnetic interactions occurring in the aggregates, whereas alternating-current susceptibility measurements find both the Dy-III analogues, 1 and 4, to show out-of-phase components at zero applied dc field, characteristic of single-molecule-magnet (SMM) behavior. Micro-SQUID studies reveal open hysteresis loops for 1, corroborating its SMM character. Further detailed complete-active-space self-consistent-field and density functional theory calculations were also performed, supporting the experimental findings in complexes 1 and 4.