Lanthanide(III) Hexanuclear Circular Helicates: Slow Magnetic Relaxation, Toroidal Arrangement of Magnetic Moments, and Magnetocaloric Effects

Abstract

Four hexanuclear circular helicates, {[Dy 6 L 6 (DMF) 12 ]•6CF 3 SO 3 •12DMF} 2 (1Dy), {[Gd 6 L 6 (DMF) 12 ]•6CF 3 SO 3 •12DMF} 2 (1Gd), [Dy 6 L 6 (DMF) 10 (H 2 O) 2 ]•6ClO 4 •4H 2 O•10DMF (2Dy), and [Gd 6 L 6 (DMF) 12 ]•6ClO 4 •2H 2 O•10DMF (2Gd) were synthesized by employing glutaratedihydrazide-bridged bis(3methoxysalicylaldehyde) ligand (H 2 L) and characterized structurally and magnetically. Direct-current (dc) magnetic susceptibility studies indicated predominant weak antiferromagnetic exchange interactions among gadolinium analogues, which were quantified using the PHI software giving J =-0.003 cm-1 with g = 2.00 for 1Gd and J =-0.001 cm-1 with g = 2.02 for 2Gd. Alternating-current (ac) magnetic susceptibility measurements indicated that complexes 1Dy and 2Dy show slow relaxation of magnetization behavior, further supported by theoretical calculations that also highlight toroidal arrangement of the magnetic moments.

Lanthanide-Based Single-Molecule Magnets Derived from Schiff Base Ligands of Salicylaldehyde Derivatives

“…In order to understand the magnetic relaxation dynamics of 47, AC susceptibility measurement was done at zero DC magnetic field in the temperature range 2.0-15.0 K and frequency 111-3111 Hz. As shown in Figure 27f [95], there is no obvious frequency dependence below 15.0 K in the in-of-phase (χ ) component susceptibility for 47, however, the out-of-phase susceptibility (χ ) clearly displays frequency-dependent signals below 10 K, but no well-defined peaks are seen till the temperature drops to 2.0 K, which may be due to quantum tunneling of the magnetization(QTM) [98]. 48) [99], where (H 2 L19) are o-phenolsalicylimine (comprising of two similar coordination pockets for Dy encapsulation) (Figure 28a).…”

Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

“…As displayed in Figure S9 and Figure 5, there is no non-zero out-of-phase signal for complex 2 while complex 3 exhibits clear temperature-dependent χ" components, indicating slow relaxation of magnetization behavior in 3. However, no visible peaks of the χ" signals are found for complex 3, which can be attributed to the fast quantum tunneling of magnetization (QTM) [44,45]. Accordingly, frequency-dependent ac magnetic susceptibilities for 3 were investigated at 2 K under dc field range of 200-4900 Oe to determine the optimized external field for suppressing the QTM.…”

Dysprosium(iii) compounds assembled via a versatile ligand incorporating salicylic hydrazide and 8-hydroxyquinolin units: syntheses, structures and magnetic properties

“…[12][13][14][15][16][17][18][19][20][21] In particular, judicious optimization of the crystal field resulted in magnetic bistability persisting up to 80 K recently in a dysprosium metallocene, which allows access to the operating temperature above liquid nitrogen, a critical point to the practical application. 22 Notably, Dy-based SMMs of varying nuclearities and topologies range over as single, dimeric, [23][24][25][26] triangular, 5,27 cube, 28,29 rhombus, 30 defect-dicubane, [31][32][33] tetrahedron, 34,35 square-based pyramid, 20,36 wheel, [37][38][39] nanotubes, 40 and so forth. To the best of our knowledge, one of the most important factors that realize the tailor-made of functional SMMs is the design of organic ligands.…”