Reactions of [Mn₆O₂(piv)₁₀(py)_2.5(piv)_1.5], Ln(NO₃)₃·6H₂O and N-mdeaH₂ in MeCN in the presence of Me₃SiCl generated a family of octanuclear Mn/Ln complexes [Mn₆^IIIMn^IILn(N-mdea)₃(N-mdeaH)(piv)₈O₂(OH)₃(NO₃)(H₂O)]·xCH₃CN·xH₂O [Ln = Gd (1), Dy (2), Er (3), pivH = pivalic acid, N-mdeaH₂ = N-methyl diethanolamine]. Each complex possesses a [Mn₆^IIIMn^IILn(μ₃-O)₂(μ₃-OH)₃]¹⁶⁺ core containing two butterfly-like subunits of [Mn₃Ln(μ₃-OH)₂] and [Mn₄(μ₃-O)₂] sharing a common vertex, and an outer Mn atom ligated to one of the subunits through a μ₃-OH⁻ ligand. The core topology represents a new Mn/Ln core type. The magnetic susceptibility study of 1–3 indicates the presence of dominant antiferromagnetic interactions within the complexes. For complex 1, which contains an isotropic Gd^III atom, fitting of the obtained M/(Nμ_B) vs. H/T data gave S = 4, g = 1.90, and D = −0.31 cm⁻¹. The results were further supported by ac data. Complex 3 exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM.