Slow Magnetic Relaxation in Mononuclear Octahedral Manganese(III) Complexes with Dibenzoylmethanide Ligands

The structural characterization and magnetic studies of three mononuclear Mn-III complexes based on the dibenzoylmethanido (dbm(-)) ligand, Mn(dbm)(3) (1) and [Mn(dbm)(2)(L)(2)](ClO4) (L = dimethyl sulfoxide, 2; L = pyridine, 3), are reported. The Mn-III ions are in an axially elongated octahedral coordination geometry. The axial zero-field-splitting parameters D, ranging from -3.42 to -4.52 cm(-1) for the three complexes, were obtained by fitting magnetic-susceptibility and magnetization data. Ab initio calculations also show the axial magnetic anisotropy in the molecules of 1-3. With an applied dc field, the ac susceptibility measurements reveal slow magnetic relaxation in 1-3. The possible relationship between the structures and the magnetic properties in these complexes are discussed.