Structure changes from radical-3d ring dimer to radical-3d-4f 1D chain with different magnetic properties

An unreported nitronyl nitroxide radical ligand and its corresponding radical-4f (complexes 1-3) and radical-3d -4f complexes (complexes 4-6) were successfully prepared. Structural analyses indicate that the complexes 1-3 are cyclic structures consist of two identical units of Ln(hfac)(3)(NIT-5-OCH3-3pyridine) (hfac = hexa-fluoroacetylacetone; Ln = Gd 1, Tb 2, Dy 3), while the complexes 4-6 show 1D zigzag structures with periodic [Rad-Ln-Rad-Cu] (Ln = Gd 4, Tb 5, Dy 6) units. Dc susceptibility measurements reveal that two different magnetic interactions coexist in complex 1: (i) ferromagnetic coupling between Gd3+ and radical through the NeO group, (ii) weak antiferromagnetic interaction between Gd3+ and radical through the pyridine ring. While for complex 4, weak ferromagnetic coupling between Cu2+/Ln(3+) and radical ligands as well as anti-ferromagnetic coupling between two adjacent radicals via the Ln(3+) are observed at the same time. Furthermore, AC magnetic studies reveal that complexes 2, 3 and 5 display slow magnetization relaxation at low-temperature.