Meta-Atom Behavior in Clusters Revealing Large Spin Ground States

The
field of single molecule magnetism remains predicated on super-
and double exchange mechanisms to engender large spin ground states.
An alternative approach to achieving high-spin architectures involves
synthesizing weak-field clusters featuring close M–M interactions
to produce a single valence orbital manifold. Population of this orbital
manifold in accordance with Hund’s rules could potentially
yield thermally persistent high-spin ground states under which the
valence electrons remain coupled. We now demonstrate this effect with
a reduced hexanuclear iron cluster that achieves an S = 19/2 (χMT ≈ 53 cm3 K/mol) ground
state that persists to 300 K, representing the largest spin ground
state persistent to room temperature reported to date. The reduced
cluster displays single molecule magnet behavior manifest in both
variable-temperature zero-field 57Fe Mössbauer and
magnetometry with a spin reversal barrier of 42.5(8) cm–1 and a magnetic blocking temperature of 2.9 K (0.059 K/min).