Large Magnetic Anisotropy in a Coupled Dinuclear FeII Single-Molecule Magnet

A series of [Me2indM(μ-Cl)(THF)]2 (M = Zn, Mn, Fe) dimers utilizing a novel bulky indoline ligand (Me2indH = 5-methoxy-2,2-dimethyl-3,3-diphenyl-7-diphenylmethylindoline) were synthesized and magnetically characterized. Analysis of the single crystal structure reveals each of the complexes exhibits distorted tetrahedral geometry about the metal center. Static magnetic measurements of 3-Fe demonstrate ferromagnetic coupling (J = 3.05 cm-1) between the Fe ions and an exceptionally high axial anisotropy (D = -33.8 cm-1). Theoretical investigations reveal that the magnetic anisotropy vectors of the two metal centers are largely coaxial along the metal-metal direction. Dynamic magnetic measurements display out-of-phase behavior indicating that 3-Fe acts as a single-molecule magnet with a Ueff of 43.3(5) cm-1.