Magnetic Anisotropy and Spin Coupling in a Cobalt(II) Dimer with Bioinspired Bridges

High Resolution Image Download MS PowerPoint Slide Cobalt(II) metal complexes constitute a versatile platform for investigating how coordination geometry and spin–orbit coupling determine their magnetic properties. Although numerous cobalt(II) coordination complexes have been reported in recent literature, only a limited number exhibit comprehensive and quantitatively reliable magnetic characterization. In this work, we investigate the magnetic properties of the hexacoordinated cobalt dimer [Co 2 (μ-L1H) 2 (μ-H 2 O) 2 (H 2 O) 4 ]4NO 3 ·2H 2 O, where L1H denotes the adenine bridging ligand. The hexacoordinated environment stabilizes a high-spin S = 3/2 configuration for both Co(II) centers, resulting in strong spin–orbit coupling and significant zero-field splitting, described by axial ( D ) and rhombic ( E ) anisotropy parameters. Fits to magnetic susceptibility and magnetization data reveal antiferromagnetic coupling between the Co(II) ions, with a ratio of E / D ≈ 1/4 and D / k B = 89 K, evidencing pronounced magnetic anisotropy in the system. This behavior is further supported by anisotropic Landé factors g x = g y = 2.5 and g z = 2.4, consistent with easy-plane magnetic anisotropy.