Dinuclear Lanthanide Complexes Based on a Schiff‐base Ligand: Free Lattice Solvent Inducing the Single Molecule Magnet Behavior of Dy₂ Compound

Abstract

Syntheses, crystal structures and magnetic properties are described for a series of seven‐coordinate dinuclear lanthanide complexes of compositions Dy2L2 (1) (H3L=2‐{[bis(2‐hydroxy‐3‐ethoxybenzyl)(aminoethyl)amino]methyl}phenol) and Ln2L2⋅MeCN (Ln=Dy (2), Sm (3), Eu (4), Gd (5), Tb (6), Ho (7)). The reaction of Dy(NO3)3⋅6 H2O with one equivalent of H3L at 70 °C in DMF/EtOH under autogenous pressure gave compound 1. Complexes 2–7 were prepared by means of the same method as that used for 1, except DMF was replaced by MeCN as the reaction solvent and Dy(NO3)3⋅6 H2O was changed to the corresponding lanthanide salts. Complexes 1–7 possess the similar Ln2 cores bridged by μ2‐phenoxyl oxygen atoms. The slight difference between 1 and 2–7 arises from the existence of free MeCN molecule in 2–7. The purposeful introduction of solvent MeCN molecule changes the crystal system from triclinic for 1 to monoclinic for 2 and alters the Dy—O–Dy angles and Dy⋅⋅⋅Dy distances, consequentially resulting into dramatic influences on the magnetic properties of 1 and 2. Complex 1 shows no SMM character, while compound 2 with free MeCN molecule exhibits a field‐induced slow magnetization relaxation behavior. Complete active space self‐consistent field (CASSCF) calculations were performed on two Dy2 compounds to rationalize the observed difference in the magnetic behavior. Theoretical calculations reveal that the energy gap between the lowest two Kramers doublets of individual DyIII fragment for 2 is higher than those of 1 (1_a and 1_b). This conlusion is consistant with the experimental result that complex 2 exhibits better magnetic properties. This work proposes an ingenious strategy for inducing the SMM behavior in the Dy2 compounds.

Magnetic Improvement and Relaxation Mechanism of the Tb-Phthalocyanine Single-Molecule Magnet by Absorbing CH2Cl2 Molecules

“…Additionally, the Pc–Tb–Pc angle of TbPc 2 ·CH 2 Cl 2 is 179.715°, which is of the same magnitude as reported previously , and larger than that of TbPc 2 (179.104°). The chemical structure, including bond angles and bond lengths between the metal center and ligands, and the twist angle between ligands can influence the magnetic relaxation process of SMMs. ,,, …”

“…The chemical structure, including bond angles and bond lengths between the metal center and ligands, and the twist angle between ligands can influence the magnetic relaxation process of SMMs. 18,23,50,51 To study the magnetic properties of TbPc 2 and TbPc 2 • CH 2 Cl 2 , the temperature dependence of molar magnetic susceptibility (χ M ) was measured in the temperature range of 2−300 K under a 1 kOe dc field. The χ M values of TbPc 2 and TbPc 2 •CH 2 Cl 2 are shown in Figure 3(a,b), respectively.…”

“…Recent developments show that the magnetic behavior of the lanthanide-based SMMs can be significantly affected by various factors, such as organic ligand modification, the external environment, magnetic dilution, counterions, and the spatial arrangement of molecules. − ,,− The dysprosium metallocene cation can display magnetic hysteresis at 80 K with short Dy–Cp cent distances and the wide Cp–Dy–Cp bending angle achieved by varying the Cp ligand framework . The magnetic properties of [Dy­(tta) 3 (L)]·C 6 H 14 can be enhanced through dilution in an amorphous or an isomorphous molecule .…”

A mixed-valence [CoII 4CoIII 2] cluster with defect disk-shaped topology

“…Several synthetic methodologies towards polynuclear cobalt clusters were established and one of the most efficient approaches involves the employment of hydroxy-containing Schiff base ligands. Schiff base ligands are easy to synthesize and their steric properties can be tuned by varying the size of the amine or carbonyl substituents (Qin et al, 2017(Qin et al, , 2018Ge et al, 2018;Li et al, 2021). More importantly, the hydroxy moieties of the Schiff base ligands can combine many metal ions with -O bridges, resulting in the formation of large polynuclear clusters.…”

Significantly Enhancing the Single-Molecule-Magnet Performance of a Dinuclear Dy(III) Complex by Utilizing an Asymmetric Auxiliary Organic Ligand

“…For Dy 2 SMMs, there are two principal means of regulating their magnetic relaxation behavior. On one hand, the exchange coupling can be increased by using bridging radicals, heavier elements with more diffuse orbitals (such as Cl andS), aromatic cyclooctatetraenide (COT 2– ), and so on. − On the other hand, the coordination environment of Dy III ions can be modulated by a subtle change in the crystal field, including varying the organic ligands in the original complexes, the lattice solvents, and the coordinated solvents. , In 2011, Murugesu et al reported a Dy 2 SMM, namely [Dy III 2 (L) 2 (NO 3 ) 2 ] ( Dy 2 -NO 3 , H 2 L = N 1, N 3-bis­(3-methoxysalicylidene)­diethylenetriamine), in which each Dy III ion coordinates one terminal nitrate anionic ligand . It was shown that the coordinated NO 3 – could be replaced by other bidentate, monoanionic ligands.…”