Synthetic Factors Determining the Curvature and Nuclearity of the Giant Mn 70 and Mn 84 Clusters with a Torus Structure of ∼4 nm Diameter.

New members of the Mn 70 and Mn 84 torus-like cluster family have been prepared from a hybrid comproportionation-alcoholysis reaction of [Mn 12 O 12 (O 2 CR) 16 (H 2 O) 4 ] in alcohol in the presence of R'CO 2 H with N n BuMnO 4 or Mn II salts as initiators. Reactions using MeCO 2 H in n PrOH or n BuOH gave [Mn 70 O 60 (O 2 CMe) 70 (O n Pr) 20 ( n PrOH) 18.5 (H 2 O) 21.5 ] ( 3 ) and [Mn 70 O 60 (O 2 CMe) 70 (OH) 3 (O n Bu) 17 ( n BuOH) 7.5 (H 2 O) 32.5 ] ( 4 ), respectively, whereas EtCO 2 H in n PrOH gave [Mn 84 O 72 (O 2 CEt) 84 (O n Pr) 24 ( n PrOH) 16 (H 2 O) 32 ] ( 5 ). They consist of alternating near-linear [Mn 3 (μ 3 -O) 4 ] + and distorted-cubane [Mn 4 (μ 3 -O) 2 (μ 3 -OR) 2 ] 6+ units bridged by syn,syn-μ-RCO 2 - and μ 3 -O 2- groups and overall are [Mn 14 ] 5 and [Mn 14 ] 6 oligomers, the repeating unit containing two Mn 3 and two Mn 4 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 Mn 70 /Mn 84 tori now available, we conclude that the Mn 70 vs Mn 84 nuclearity is determined by the relative bulk of the carboxylates vs the alkoxides, their increasing bulk favoring Mn 84 and Mn 70 , respectively, with carboxylates larger than acetate giving Mn 84 . 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 [Mn 14 ] n torus family of giant single-molecule magnets (SMMs), in which Mn 84 and Mn 70 are the largest homometallic Mn/O clusters and SMMs to date.