Single-Molecule Magnetism in a Pentacoordinate Cobalt(II) Complex Supported by an Antenna Ligand

Pentacoordinate
complex [CoL3Cl2] with a tridentate antenna-like
ligand L3 forms a dimer held by short π–π
stacking with head-to-head contacts at 3.4 Å. The direct-current
(dc) magnetic susceptibility and magnetization data confirm weak ferromagnetic
interaction and a large-magnetic anisotropy, D/hc = 150 cm–1 and E/hc = 11.6 cm–1. The system shows superparamagnetic
behavior at low temperature that depends upon the applied magnetic
field. At Bdc = 0.2 T, a low-frequency
peak at the out-of-phase susceptibility is seen (ν ∼
0.3 Hz), whereas the onset of the second peak appears at ν >
1500 Hz, indicating the existence of two slow relaxation processes.