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 {Mn3} core arranged in a linear fashion. The previously reported complex 1, [MnIV3(dpo)6]·2MeCN, where H2dpo is (E)-1-hydroxy-1,1-diphenylpropan-2-one oxime, served as a starting point for the isolation of a {Mn3} compound with an analogous core arrangement through the reaction of Mn­(OAc)2·4H2O, H3oxol ((E)-2,5-dihydroxy-2,5-dimethylhexan-3-one oxime), and NaOH in MeOH and MeCN. By using these reaction conditions, compound 2, Na­[MnIV2MnIII(Hoxol)6]n·MeOH·H2O, was successfully isolated revealing a central MnIII ion thereby introducing structural and magnetic anisotropy to the system. The structure of 2 reveals linear trinuclear MnIV–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° 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 MnIII 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 MnIV–MnIII–MnIV SMMs.