Turning on Single-Molecule Magnet Behavior in a Linear {Mn3} Compound

The synthesis, structure, and magnetic properties are reported for a new manganese compound with a mixed-valent {Mn-3} core arranged in a linear fashion. The previously reported complex 1, [Mn-3(IV)(dpo)(6)]center dot 2MeCN, where H(2)dpo is (E)-1-hydroxy-1,1-diphenylpropan-2-one oxime, served as a starting point for the isolation of a {Mn-3} compound with an analogous core arrangement through the reaction of Mn-(OAc)2 center dot 4H(2)O, H(3)oxol ( (E)-2,5-dihydroxy-2,S-dimethylhexan-3-one oxime), and NaOH in MeOH and MeCN. By using these reaction conditions, compound 2, Na[(Mn2MnIII)-Mn-IV(Hoxol)(6)](n)center dot MeOH center dot H2O, was successfully isolated revealing a central Mn-III ion thereby introducing structural and magnetic anisotropy to the system. The structure of 2 reveals linear trinuclear Mn-IV-(MnIII-MnIV) units connected through Na+ ions forming a linear one-dimensional coordination polymer. The Jahn-Teller axes of each trinuclear unit are aligned parallel within the same chain and form a 75 degrees angle between the two symmetry related chains. Magnetic susceptibility measurements of 1 and 2 in the temperature range 1.9-300 K reveal that only the reduced compound, 2, is a single-molecule magnet (SMM) largely due to the anisotropy introduced by the Jahn-Teller distortions on the Mn-III ions, which effectively induce this magnet behavior. Weak antiferromagnetic interactions along the chains through the Na+ cations lead to a modulation of the intrinsic properties of the Mn-IV-Mn-III-Mn-IV SMMs.