Enhancing Magnetic Relaxation of Dy‐Radical Networks by Tuning the Ligand Field and Magnetic Interactions

A series of two‐dimensional Ln‐nitronyl nitroxide radical coordination networks, namely, {[Ln(hfac) 3 ] 3 (NITBzald) 2 } n (Ln = Gd 1 and Dy 2 ; NITBzald = 2‐(4‐benzaldehyde)‐4,4,5,5‐tetramethylimidazoline‐l‐oxyl‐3oxide; hfac = hexafluoroacetylacetone) and {[Dy(tfa) 3 ] 3 (NIT‐4Py) 2 } n ( 3 ; tfa = trifluoroacetylacetonato; NIT‐4Py = 2‐(4‐pyridyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide) were synthesized. These complexes are composed of five‐spin magnetic building blocks ([Ln 3 (NIT) 2 ]) formed by three Ln III ions bridged by two NIT units which are extended into 2D structure via coordinated aldehyde or pyridine groups of the radicals. DC magnetic investigations indicate that ferromagnetic Dy–NO interactions dominate in complex 3 whereas antiferromagnetic couplings in complex 2 are predominant. AC magnetic susceptibility studies show that complex 2 just exhibits the onset of slow relaxation of the magnetization while complex 3 presents visible maxima of temperature/frequency‐dependent χ ″ signals under a zero dc field, evidencing SMM behavior. The observed distinct magnetic relaxation performances of two Dy derivatives could be ascribed to synergistic effect of the different ligand fields of Dy III ions mainly arising from the distinct coligands (hfac vs. tfa) as well as magnetic exchanges.