Geometry-Mediated Enhancement of Single-Ion Anisotropy: A Route to Single-Molecule Magnets with a High Blocking Temperature†

: Not just any old iron ion: A linear, two-coordinate ionic Fe(I) complex with a S=3/2 ground state has a large energy barrier for magnetization reversal, Ueff =226 cm(-1) , and undergoes slow magnetic relaxation in the absence of an applied magnetic field. The preparation of complexes with these properties is a step towards the eventual practical application of single-molecule magnets.