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(À36.9 cmÀ1 - À74.7 cmÀ1). Surprisingly, a comparison of 2
with the previously reported chloride and bromide analogues
reveals a decrease in the energy barrier despite the significantly
larger negative D value. The relaxation event in 3 is still much
slower due to the larger magnitude of the pre-exponential factor.
The present series of mononuclear cobalt complexes further
supports the hypothesis that ligands with heavier and softer
main group donor atoms significantly enhance the global
magnetic anisotropy of the metal complexes as evidenced by
the increased ZFS parameters. This fact notwithstanding, the
dynamic magnetic properties reveal only a minor effect on the
magnitude of the energy barrier to reversing the magnetization.
A similar observation was recently reported for the [Co(EPh)4]2À
family of SMMs. More detailed experimental and computational
studies are in progress to identify the different factors leading to
such an enhancement of zero-field splitting parameters and the
underlying issues causing the lack of concomitant increase in
the energy barriers.
Research supported by the U.S. Department of Energy, Office
of Basic Energy Sciences, Division of Materials Sciences and
Engineering under Award DE-FG02-02ER45999.
Notes and references
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12268 | Chem. Commun., 2014, 50, 12266--12269
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