Inverse sandwich biphenyl complexes
[(NNTBS)Ln]2(μ-biphenyl)[K(solvent)]2 [NNTBS = 1,1′-fc(NSitBuMe2)2; Ln = Gd, Dy, Er; solvent = Et2O,
toluene; 18-crown-6], containing a quadruply reduced biphenyl ligand,
were synthesized and their magnetic properties measured. One of the
dysprosium biphenyl complexes was found to exhibit antiferromagnetic
coupling and single-molecule-magnet behavior with U
eff of 34 K under zero applied field. The solvent coordinated
to potassium affected drastically the nature of the magnetic interaction,
with the other dysprosium complex showing ferromagnetic coupling.
Ab initio calculations were performed to understand the nature of
magnetic coupling between the two lanthanide ions bridged by the anionic
arene ligand and the origin of single-molecule-magnet behavior.