Synthetic Factors Determining the Curvature and Nuclearity of the Giant Mn70 and Mn84 Clusters with a Torus Structure of ∼4 nm Diameter

New members of the Mn₇₀ and Mn₈₄ torus-like cluster family have been prepared from a hybrid comproportionation-alcoholysis reaction of [Mn₁₂O₁₂(O₂CR)₁₆(H₂O)₄] in alcohol in the presence of R'CO₂H with NⁿBuMnO₄ or Mn^II salts as initiators. Reactions using MeCO₂H in ⁿPrOH or ⁿBuOH gave [Mn₇₀O₆₀(O₂CMe)₇₀(OⁿPr)₂₀(ⁿPrOH)_18.5(H₂O)_21.5] (3) and [Mn₇₀O₆₀(O₂CMe)₇₀(OH)₃(OⁿBu)₁₇(ⁿBuOH)_7.5(H₂O)_32.5] (4), respectively, whereas EtCO₂H in ⁿPrOH gave [Mn₈₄O₇₂(O₂CEt)₈₄(OⁿPr)₂₄(ⁿPrOH)₁₆(H₂O)₃₂] (5). They consist of alternating near-linear [Mn₃(μ₃-O)₄]⁺ and distorted-cubane [Mn₄(μ₃-O)₂(μ₃-OR)₂]⁶⁺ units bridged by syn,syn-μ-RCO₂^- and μ₃-O^2- groups and overall are [Mn₁₄]₅ and [Mn₁₄]₆ oligomers, the repeating unit containing two Mn₃ and two Mn₄ units. 3/4/5 possess external diameters (including organic ligands) of 4.0/4.1/4.6 nm, respectively, and crystallize as supramolecular nanotubes but with different packing arrangements. Considering all Mn₇₀/Mn₈₄ tori now available, we conclude that the Mn₇₀ vs Mn₈₄ nuclearity is determined by the relative bulk of the carboxylates vs the alkoxides, their increasing bulk favoring Mn₈₄ and Mn₇₀, respectively, with carboxylates larger than acetate giving Mn₈₄. Alternating current (ac) magnetic susceptibility studies revealed frequency-dependent χ″_M signals below ∼2.4 K, indicating 3-5 to be new members of the giant [Mn₁₄]_n torus family of giant single-molecule magnets (SMMs), in which Mn₈₄ and Mn₇₀ are the largest homometallic Mn/O clusters and SMMs to date.