Nine new tetranuclear centrosymmetric linear complexes, [RE₄(dbm)₈L₂(DMF)₂]·nCH₂Cl₂·mC₂H₃N (RE = Y (1), Tb (2), Dy (3), Ho (4), Er (5), Lu (6)) and [RE₄(dbm)₈L₂(C₂H₅OH)₂]·nCH₃CN (RE = Tb (7), Dy (8), Ho (9)) (HL = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-8-hydroxyquinoline and dbm = 1,3-diphenyl-1,3-propanedione) have been synthesized. Complexes 1–9 are tetranuclear complexes. Magnetic studies reveal that both Dy^III-based complexes (3 and 8) exhibit single-molecule magnet (SMM) behavior under a zero dc field. Furthermore, complex 3 presents one relaxation process under a zero dc field, while application of an external dc field (1500 Oe) induces multi-relaxation signals of the ac magnetic susceptibility.