A Family of Co<sup>II</sup>Co<sup>III</sup><sub>3</sub> Single-Ion Magnets with Zero-Field Slow Magnetic Relaxation: Fine
Tuning of Energy Barrier by Remote Substituent and Counter Cation
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Abstract
The synthesis, structures, and magnetic
properties of a family
of air-stable star-shaped Co<sup>II</sup>Co<sup>III</sup><sub>3</sub> complexes were investigated. These complexes contain only one paramagnetic
Co(II) ion with the approximate <i>D</i><sub>3</sub> coordination
environment in the center and three diamagnetic Co(III) ions in the
peripheral. Magnetic studies show their slow magnetic relaxation in
the absence of an applied dc field, which is characteristic behavior
of single-molecule magnets (SMMs), caused by the individual Co(II)
ion with approximate <i>D</i><sub>3</sub> symmetry in the
center. Most importantly, it was demonstrated that the anisotropy
energy barrier can be finely tuned by the periphery substituent of
the ligand and the countercation. The anisotropy energy barrier can
be increased significantly from 38 K to 147 K
