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Spin Transitions in Trigonal Bipyramid Clusters of Group 8 Metal Ions
Catalina Achim, Department of Chemistry, Carnegie Mellon University
The current quest for increased capacity of information storage devices has fuelled intense research of moleculebased materials that can be bistable. Our research is focused on the investigation of molecules that can undergo spin
transitions between two different spin states and contain multiple Fe(II) ions. In these complexes, the spin transition can
be affected by intramolecular interactions between the metal ions.
In collaborative studies with the Dunbar group at Texas A&M, Musfeldt group at University of Tennessee, and Petasis
group at Allegheny College, we have studied a series of trigonal bipyramid clusters that contain in the equatorial positions
three Fe ions with bis(tetramethylphenantroline)bis(cyanide) coordination and in the axial positions two metal ions from the
group 8 of the periodic table with hexacyanide ligands. A combination of Mössbauer, EPR, and IR spectroscopy, X-ray
crystallography, and magnetic susceptibility studies have shown that the clusters in which the axial ions are Fe or Ru show
a LS FeII ↔ HS FeII spin transition while the clusters in which Os ions in the axial positions undergo a charge transfer
coupled spin transition. It is the first time that a transition of the latter type led to the largest possible spin change at an Fe
ion, namely from S = 0 for FeII to S = 5/2 for FeIII.
FeII LS
↔ HS Spin Transition in Fe-Fe
Fe/RuIII
FeII
LS
LS
LS
and Fe-Ru Clusters
Fe/RuIII
FeII HS
HS
HS
Charge Transfer Coupled Spin Transition in Fe-Os Clusters
OsII
HS FeIII
OsIII
LS FeII