Radical-Bridged Heterometallic Single-Molecule Magnets Incorporating Four Lanthanoceniums

The syntheses and magnetic properties of organometallic heterometallic compounds [K(THF)(6)]{Co-I[(mu(3)-HAN)RE2Cp*(4)](2)} (1-RE) and [K(Crypt)](2){Co-I[(mu(3)-HAN)RE2Cp*(4)](2)} (2-RE) containing hexaazatrinaphthylene radicals (HAN(center dot 3-)) and four rare earth (RE) ions are reported. 1-RE shows isolable species with ligand-based mixed valency as revealed by cyclic voltammetry (CV) thus leading to the isolation of 2-RE via one-electron chemical reduction. Strong electronic communication in mixed-valency supports stronger overall ferromagnetic behaviors in 2-RE than 1-RE containing Gd and Dy ions. Ac magnetic susceptibility data reveal 1-Dy and 2-Dy both exhibit slow magnetic relaxation. Importantly, larger coercive field was observed in the hysteresis of 2-Dy at 2.0 K, indicating the enhanced SMM behavior compared with 1-Dy. Ligand-based mixed-valency strategy has been used for the first time to improve the magnetic coupling in lanthanide (Ln) SMMs, thus opening up new ways to construct strongly coupled Ln-SMMs.

Automated summary

The syntheses and magnetic properties of organometallic heterometallic compounds containing hexaazatrinaphthylene radicals (HAN•3-) and rare earth (RE) ions are reported. The results show that the ligand-based mixed valency in one of the compounds leads to the isolation of another compound via one-electron chemical reduction. The compounds containing Gd and Dy ions exhibit stronger overall ferromagnetic behaviors and enhanced slow magnetic relaxation compared to those without the ligand-based mixed valency.