Four New Lanthanide−Nitronyl Nitroxide (Ln^III= Pr^III, Sm^III, Eu^III, Tm^III) Complexes and a Tb^IIIComplex Exhibiting Single-Molecule Magnet Behavior

Abstract

Five new complexes based on rare-earth-radical [Ln(hfac)(3)(NIT-5-Br-3py)](2) (Ln = Pr (1), Sm (2), Eu (3), Tb (4), Tm (5); hfac = hexafluoroacetylacetonate; NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) have been synthesized and characterized by X-ray crystal diffraction. The single-crystal structures show that these complexes have similar structures, in which a NIT-5-Br-3py molecule acts as a bridging ligand linking two Ln(III) ions through the oxygen atom of the N-O group and nitrogen atom from the pyridine ring to form a four-spin system. Both static and dynamic magnetic properties were measured for complex 4, which exhibits single-molecule magnetism behavior.

Radical ligand-containing single-molecule magnets

“…The Tb III congener (31) displays single-molecule magnet behavior under a zero dc field with a relaxation barrier of U eff = 20 cm −1 (Fig. 28) [303], while the coupling constants for the Gd III species was determined to be J 1,Gd-L = +2.60 cm −1 and J 2,Gd-L = −0.24 cm −1 [256]. A related complex, [Tb(hfac) 3 (NIT3Py)] 2 , in which meta pyridyl-substituted nitronyl nitroxide ligands link two Tb III centers, also displayed slow magnetic relaxation under a 3 kOe dc field, featuring a barrier of 13.2 cm −1 [305].…”

Magnetic and Luminescent Properties of Sm, Eu, Tb, and Dy Coordination Polymers with 2‐Hydroxynicotinic Acid

“…For 5 and 6, the χ M T values steadily decrease as T is lowered and reach 6.86 (5) and 8.82 cm 3 K mol -1 (6) at 2 K. To obtain a rough quantitative estimation of the magnetic interaction between Tb III (or Dy III ) ions, the Ln III ion could be assumed to exhibit a splitting of the m j energy levels (Ĥ = ΔĴ z 2 ) in an axial crystal field. [42,[50][51][52][53][54] The best-fit parameters are Δ = 0.050 cm Taking into account the intriguing magnetic behavior of the Dy III complex due to the ligand field, which splits the 6 H 15 /2 free ion ground state into eight half-integral Kramers doublets, the magnetic properties for 6 were studied further. As shown in Figure 6, the M versus H/T data below 5.0 K for 6 show a rapid increase of the magnetization at low magnetic field.…”

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

“…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.…”