The reaction of hetero donor chelating mannich base ligand 6,6'-{(2-(dimethylamino)ethylazanediyl)-bis(methylene)}bis(2-methoxy-4-methylphenol) with Ni(ClO4)(2)center dot 6H(2)O and lanthanide(III) salts [Dy(III) (1); Tb(III) (2); Gd (III) (3); Ho(III) (4); and Er(III) (5)] in the presence of triethylamine and pivalic acid afforded a series of heterometallic hexanuclear Ni(II)-Ln(III) coordination compounds, [Ni(3)Ln(3)(mu(3)-O)(mu(3)-OH)(3)(L)(3)(mu-OOCCMe3)(3)]center dot (ClO4)center dot wCH(3)CN center dot xCH(2)Cl(2)center dot yCH(3)OH center dot zH(2)O [for 1, w = 8, x = 3,y = 0, z = 5.5; for 2, w = 0, x = 5,y = 0, z = 6.5; for 3, w = 15, x = 18, y = 3,z = 7.5; for 4, w = 15, x = 20, y = 6, z = 9.5; and for 5, w = 0, x = 3, y = 2, z = 3]. The molecular structure of these complexes reveals the presence of a monocationic hexanuclear derivative containing one perchlorate counteranion. The asymmetric unit of each of the hexanuclear derivatives comprises the dinudear motif [NiLn(L)(mu(3)-O)(mu(3)-OH)(mu-Piv)]. The cation contains three interlinked O-capped dusters: one Ln(3)(III)O and three Ni(II)Ln(2)(III)O. Each of the lanthanide centers is eight-coordinated (distorted trigonal-dodecahedron), while the nickel centers are hexacoordinate (distorted octahedral). The study of the magnetic properties of all compounds are reported and suggests single molecule magnet behavior for the Dy(III) derivative (1).