Symmetry-breaking substitutions of [Re(CN)8]3− into the centered, face-capped octahedral clusters (CH3OH)24M9M′6(CN)48 (M = Mn, Co; M′ = Mo, W)

Abstract

The diamagnetic complex [Re(CN)₈]³⁻ is shown to react with Mn²⁺ ions in methanol to generate the centered, face-capped octahedral cluster (CH₃OH)₂₄Mn₉Re₆(CN)₄₈, which is structurally analogous to (CH₃OH)₂₄Mn₉Mo₆(CN)₄₈. Related reactions involving stoichiometric mixtures of octacyanometalate complexes generate the substituted species (CH₃OH)₂₄Mn₉Mo₅Re(CN)₄₈, (CH₃OH)₂₄Co₉Mo₅Re(CN)₄₈, (CH₃OH)₂₄Mn₉Mo₃Re₃(CN)₄₈, (CH₃OH)₂₄Mn₉W₅Re(CN)₄₈ and (CH₃OH)₂₄Co₉W₅Re(CN)₄₈, in which the O_h symmetry of the cluster core is broken. Reassessment of the magnetic properties of the Mn₉Mo₆(CN)₄₈ cluster confirm that it possesses a ground state spin of S = 39/2, but does not exhibit single-molecule-magnet behavior. Lowering the symmetry of the molecule by substitutions of Re^V at one or three of the Mo^V sites does not lead to an overall increase in the magnetic anisotropy, as probed by ac magnetic susceptibility measurements. A similar result occurs for the other substituted species, with the important exception of the new single-molecule magnet (CH₃OH)₂₄Co₉W₅Re(CN)₄₈, for which the spin reversal barrier is significantly reduced relative to that observed previously in (CH₃OH)₂₄Co₉W₆(CN)₄₈.