Utilizing 3d–4f Magnetic Interaction to Slow the Magnetic Relaxation of Heterometallic Complexes

Abstract

The synthesis, structural characterization, and magnetic properties of four related heterometallic complexes with formulas [Dy(III)2Co(II)(C7H5O2)8]·6H2O (1), [Dy(III)2Ni(II)(C7H5O2)8]·(C7H6O2)2 (2), Tb(III)2Co(II)(C7H5O2)8 (3), and Dy(III)2Cd(II)(C7H5O2)8 (4) were reported. Each of complexes has a perfectly linear arrangement of the metal ions with two terminal Ln(III) (Ln(III) = Dy(III), Tb(III)) ions and one central M(II) (M(II) = Co(II), Ni(II), Cd(II)) ion. It was found that 1-3 displayed obvious magnetic interactions between the spin carriers according to the direct current (dc) susceptibility measurements. Alternating current (ac) magnetic susceptibility measurements indicate that complexes 1-4 all exhibit single-molecule magnet (SMM) behavior, while the replacement of the diamagnetic Cd(II) by paramagnetic ions leads to a significant slowing of the relaxation thanks to the magnetic interactions between 3d and 4f ions, resulting in higher relaxation barrier for complexes 1 and 2. Moreover, both Dy2Co and Dy2Ni compounds exhibit dual relaxation pathways that may originate from the single ion behavior of individual Dy(III) ions and the coupling between Dy(III) and Co(II)/Ni(II) ions, respectively, which can be taken as the feature of 3d-4f SMMs. The Ueff for 1 of 127 K is a relatively high value among the reported 3d-4f SMMs. The results demonstrate that the magnetic coupling between 3d and 4f ions is crucial to optimize SMM parameters. The synthetic approach illustrated in this work represents an efficient route to design nd-4f based SMMs via incorporating suitable paramagnetic 3d and even 4d and 5d ions into the d-f system.

Selective arc-discharge synthesis of Dy2S-clusterfullerenes and their isomer-dependent single molecule magnetism

“…Two linear regimes in the temperature dependence of relaxation rates have been observed for several 3d–4f SMMs. In these complexes, the low-temperature process corresponds to the relaxation via exchange excited states, whereas the higher-energy barrier is due to the Orbach relaxation via the crystal-field excited state of the lanthanide ions 23,68,69…”

Synthesis, Structure and Magnetic Properties of Mn2Tb2 Tetranuclear Complex with p‐tert‐Butylthiacalix[4]arene

“…Since Condorelli et al. have reported first 3d‐4f heterometallic complexes with organic ligands, a large number of heterometallic complexes have been investigated, but so far, there is no full clarity on magnetic couplings in such systems, and intensive research has continued . It is known that multidentate ligands are effective for the construction of polynuclear heterometallic compounds .…”

Axial Ligand Field in D4d Coordination Symmetry: Magnetic Relaxation of Dy SMMs Perturbed by Counteranions

“…The solid lines indicate the best fits to the experiments with the generalized Debye model.Cole-Cole plots of χ'' vs. χ'(Figure 4) reveal semicircular profiles, indicating a single relaxation process is operative for all complexes. The plots were fitted to a generalized Debye model with relatively small α parameters being in the range 0.04-0.26 (1•OH), 0.07-0.32 (2•Cl) and 0.08-0.24 (3•Br), indicating a very narrow distribution of relaxation times for each complex [80][81][82].…”