Slow Magnetization Relaxation in a Family of Triangular {CoIII2LnIII} Clusters: The Effect of Diamagnetic CoIII Ions on the LnIII Magnetic Dynamics

The first use of the Schiff base chelate N‐naphthalidene‐o‐aminophenol (naphH2) in Co/Ln chemistry has afforded a family of isostructural [CoIII2LnIII(OMe)2(naph)2(O2CMe)3(MeOH)2] (Ln = Tb, Dy and Er) complexes, revealing a rare {CoIII2Ln(μ3‐OMe)}8+ triangular core composed of two diamagnetic CoIII ions and a 4f‐ion with slightly distorted square antiprismatic geometry. Alternating current (ac) magnetic susceptibility studies revealed that {Co2Dy}, and its magnetic diluted analogue {Co2Dy0.05Y0.95}, behave as mononuclear single‐molecule magnets (SMMs) with similar energy barriers for the magnetization reversal, Ueff, of ~85‐90 K. SMM properties were also detected for {Co2Er}, with the compound exhibiting a Ueff of 18.7 K under an applied magnetic field of 800 Oe. To interpret the experimental magnetic results, ab initio CASSCF/RASSI‐SO and DFT calculations were performed as a means of exploring the single‐ion characteristics of LnIII ions and comprehend the role of the diamagnetic CoIII ions in the magnetization relaxation of the three heterometallic compounds.