Modulating spin dynamics of cyclic LnIII-radical complexes (LnIII = Tb, Dy) by using phenyltrifluoroacetylacetonate coligand

Abstract

Three novel ring-like compounds formulated as [Ln(Phtfac)(3)(NITpPy)](2) (Ln(III) = Gd 1, Tb 2, Dy 3; HPhtfac = 4,4,4-trifluoro-1-phenylbutane-1,3-dione; NITpPy = 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide) were synthesized and structurally and magnetically characterized. Three compounds possess cyclic dimer structure in which each pyridine substituted radical links two different metal ions through the oxygen of nitroxide group and the pyridine nitrogen. DC magnetic studies show the Ln(III) ion interacts ferromagnetically with the directly bonding nitronyl nitroxide. Both Tb(III) and Dy(III) clusters show frequency-dependent ac magnetic susceptibilities, indicating single-molecule magnet behavior. It is demonstrated that the β-diketonate coligand may play an important role in determining the magnetic relaxation for the lanthanide-radical system.

Radical ligand-containing single-molecule magnets

“…Although phenol-substituted nitronyl nitroxide compound [Dy(hfac) 2 (NITPhO)] 2 shows a small relaxation barrier of U eff = 5.3 cm −1 [308], the related Dy III species with a brominated phenol-substituted nitronyl nitroxide radical does not show slow magnetic relaxation. Finally, ac magnetic susceptibility measurements performed on the phenyltrifluoroacetylacetonate (Phtfac)-containing complexes [Tb(Phtfac) 3 and [Dy(Phtfac) 3 (NIT4Py)] 2 revealed relaxation barriers of 18 and 14 cm −1 , respectively, under a 3-kOe dc field [271]. The analogous complex [Gd(Phtfac) 3 (NIT4Py)] 2 exhibits ferromagnetic coupling, with constants of J Gd-L1 = 1.84 cm −1 and J Gd-L2 = 0.12 cm −1 [271].…”

“…Finally, ac magnetic susceptibility measurements performed on the phenyltrifluoroacetylacetonate (Phtfac)-containing complexes [Tb(Phtfac) 3 and [Dy(Phtfac) 3 (NIT4Py)] 2 revealed relaxation barriers of 18 and 14 cm −1 , respectively, under a 3-kOe dc field [271]. The analogous complex [Gd(Phtfac) 3 (NIT4Py)] 2 exhibits ferromagnetic coupling, with constants of J Gd-L1 = 1.84 cm −1 and J Gd-L2 = 0.12 cm −1 [271].…”

Synthesis, Crystal Structure, and Magnetic Property of New Trispin Ln(III)‐Nitronyl Nitroxide Complexes

“…For the reported SMMs containing lanthanide ions, the slow magnetic relaxation mainly results from single‐ion relaxation, which is extremely sensitive to the strength and symmetry of the local crystal field around the lanthanide center . Comparison of the magnetic behaviors of complexes 3 and 4 with those of previously reported Ln(III)‐radical SMMs , no SMM behavior is found for 3 and 4 . It indicates that NITPh(MeO) 2 is not the suitable ligand for the superparamagnetic systems in this kind of Ln(III)‐radical complexes.…”

“…Tb(III) and Dy(III) are usually selected to construct SMMs or SCMs compounds, due to their large magnetic anisotropy . For the reported SMMs containing lanthanide ions, the slow magnetic relaxation mainly results from single‐ion relaxation, which is extremely sensitive to the strength and symmetry of the local crystal field around the lanthanide center . Comparison of the magnetic behaviors of complexes 3 and 4 with those of previously reported Ln(III)‐radical SMMs , no SMM behavior is found for 3 and 4 .…”

“…Since the discovery of first single chain magnet [Co(hfac) 2 (NITPhMeO)] by Gatteschi , lanthanide‐radical approach has become an effective method to obtain the slow‐relaxing molecular magnets, such as single chain magnets (SCMs) , single molecule magnets (SMMs) , and other particular magnetic systems . In these designing strategies, Tb(III) and Dy(III) are selected as preferred central ions due to their large magnetic anisotropy.…”