Two Dy(III) Single-Molecule Magnets with Their Performance Tuned by Schiff Base Ligands

Abstract

To develop new lanthanide single-molecule m a g n e t s ( S M M s ) , t w o n e w c o m p l e x e s o f [Dy 2 (MeOH) 2 (HL 1 ) 2 (NO 3 ) 2 ]•2MeOH (1) and [Dy 6(2) were obtained by reacting Dy(NO) 3 •6H 2 O with 3-amino-1,2-propanediol in the presence of 2-hydroxynaphthaldehyde for 1 and by reacting DyCl 3 •6H 2 O with 1,1-di-(hydroxymethyl)ethylamine in the presence of 2-hydroxynaphthaldehyde for 2, respectively, in which the Schiff base ligands of 3-(((2-hydroxynaphthaen-1-yl)methylene)amino)propane-1,2-diol (H 3 L 1 ) and 2-(β-naphthalideneamino)-2-(hydroxylmethyl)-1-propanol (H 3 L 2 ) were in situ formed. The two Dy(III) ions in 1 are linked by two O alkoxy atoms of two (HL 1 ) 2− ligands to build a dinuclear skeleton. Complex 2 presents a nearly planar hexanuclear skeleton constructed from four edge-shared triangular Dy 3 units with the two peripheral Dy 3 units consolidated by two μ 3 -O bridges and the two central Dy 3 units consolidated by one μ 3 -O bridge. Obviously, they exhibit a different topological arrangement resulting from the linkage of the Schiff base ligands. Both of them are typical SMMs under zero dc fields, with a U eff /k B value of 34 K for 1 and 40 K for 2, respectively. Multiple processes are involved in the relaxation processes of 1 and 2. The different SMM performances of the two titled complexes reveal a tuning effect of Schiff base ligands through tuning the coordination environments and topological arrangements of dysprosium(III) ions, which is supported by the theoretical calculations.

Chirality and Magnetic Properties of One‐dimensional Ln (Ln = Gd, Dy) Polymers

“…For Dy , the curve shape of χ M T – T indicates the magnetic interaction between spins is completely different from Gd . At room temperature, the χ M T value is 14.30 cm 3 · K · mol –1 , which corresponds to the expected 14.7 cm 3 · K · mol –1 ( 6 H 15/2 and g = 4/3) for one isolated Dy III ion , . With cooling, χ M T value steadily and brings down to minimum value of 11.74 cm 3 · K · mol –1 at 20.0 K, which is mainly ascribed to the thermal depopulation of Stark sublevels of Dy III ion .…”

“…At room temperature, the χ M T value is 14.30 cm 3 · K · mol –1 , which corresponds to the expected 14.7 cm 3 · K · mol –1 ( 6 H 15/2 and g = 4/3) for one isolated Dy III ion , . With cooling, χ M T value steadily and brings down to minimum value of 11.74 cm 3 · K · mol –1 at 20.0 K, which is mainly ascribed to the thermal depopulation of Stark sublevels of Dy III ion . Below this temperature, χ M T suddenly increases to 20.38 cm 3 · K · mol –1 at 1.8 K, indicating that there exists the ferromagnetic interaction between Dy III ions and it is strong enough to overcome the decline of χ M T caused by the thermal depopulation , .…”

“…The isothermal field‐dependent magnetization ( M‐H ) of Gd and Dy were measured at low temperature (1.8–10 K) (Figures S10 and 11, Supporting Information). At 1.8 K, the M value rises slowly with the H increase and reaches 5.96 ( Gd ), 5.27 ( Dy ) N μ B at 7 T, which are smaller than the calculated value 7 N μB for Gd and 10 N μ B for Dy Besides, the non‐superposition of the M vs. H/T curves indicates the existence of strong magnetic anisotropy for complex Dy (Figure S12, Supporting Information) . The magnetization data of Gd was calculated at the field of 0–9 K between 0 and 7 T by the Maxwell relation in equation Δ S m ( T ) = ∫[ ∂M(T, H )/ ∂T ] H dH (Figure ) .…”

“…In the light of magnetic properties, the lanthanide ions, as evidenced by the rising research, have attracted plentiful attention on establishment both single‐chain magnets (SCMs) and single‐molecule magnets (SMMs) as well as magnetocaloric effect (MCEs),, on account of the magnetic anisotropy or the large‐spin multiplicity of the spin ground‐state , . To the best of our knowledge, lanthanide ions own the individual 4f electronic structures, resulting high and changing coordination numbers, large magnetic effects and so on, which is favored for the potential applications in magnetic fields, etc , .…”

Temperature‐induced formation of two dinuclear dysprosium complexes with different magnetic properties

“…The α for the complex falls within the range of 0.01–0.5, which envelopes the susceptibility observed for Dy‐based SMMs and suggests a narrow to moderate distribution of magnetic relaxation. The temperature‐dependent relaxation time was analyzed by assuming a thermally activated process following the Arrhenius law [ τ = τ 0 exp ( U eff / k B T )] . The energy barriers and extrapolated relaxation times were U eff = 2.66 K and τ 0 = 2.0 × 10 −4 s for 2 under a 0 DC field (Figure a), respectively, and were U eff = 8.43 K and τ 0 = 8.56 × 10 −4 s under a 1500 Oe DC field (Figure b), respectively.…”