Single-Molecule Magnets:  A Mn₂₅ Complex with a Record S = 51/2 Spin for a Molecular Species

The reaction of MnCl₂·4H₂O (3 equiv), pyridine-2,6-dimethanol (pdmH₂) (10 equiv), and NaN₃ (10 equiv) in MeOH/MeCN (1:2 v/v) with NMe₄OH (1 equiv) gave [Mn₂₅O₁₈(OH)₂(N₃)₁₂(pdm)₆(pdmH)₆](Cl)₂·12MeCN (1·12MeCN) in ∼30% yield. The cation of complex 1 comprises five Mn_x layers of three types in an ABCBA arrangement. Fitting of variable-temperature and -field magnetization data establishes that 1 has an S = 51/2 ground state, the largest value for a molecular species. The complex also displays hysteresis loops below 0.6 K in magnetization vs applied field sweeps, establishing it as the largest spin single-molecule magnet to date.