Large Easy‐Plane Magnetic Anisotropy in a Three‐Coordinate Cobalt(II) Complex [Li(THF)₄][Co(NPh₂)₃]

Magnetic anisotropy is the key element in the construction of single-ion magnets, a kind of nanomagnets for high-density information storage. This works describes an unusual large easy-plane magnetic anisotropy (with a zero-field splitting parameter D of +40.2 cm^-1 ), mainly arising from the second-order spin-orbit coupling effect in a trigonal-planar Co^II complex [Li(THF)₄ ][Co(NPh₂ )₃ ], revealed by combined studies of magnetism, high frequency/field electron paramagnetic resonance spectroscopy, and ab initio calculations. Meanwhile, the field-induced slow magnetic relaxation in this complex was mainly attributed to the Raman process.