Influence of Energy Barriers in Triangular Dysprosium Single-Molecule Magnets through Different Substitutions on a Nitrophenolate-Type Coligand

Abstract

The effect of the directions of the anisotropy axes on the energy barriers of single-molecule magnets (SMMs) was investigated. By introducing nitrophenolate (NP)-type coligands with different substitutions, the energy barrier was significantly changed. The structural and magnetic properties of three novel SMMs based on trinuclear {Dy3O5} phenoxo- and methoxyl-bridged triangular motifs were explored. All complexes share the formula [Dy3(Hhmb)4(μ3-OMe)2(OMe)­(NP)]­[Dy3(Hhmb)4(μ3-OMe)2(NP)]·solvent·3Cl, where Hhmb = (2-hydroxy-3-methoxyphenyl)­methylene­(benzoicotino)­hydrazine, secondary ligand NP = 2-nitrophenol (2-NP, complex 1), 2,4-dinitrophenol (2,4-DNP, complex 2), and 2,4,6-trinitrophenol (2,4,6-TNP, complex 3), and solvent = 2MeOH·2Et2O (1) and 4MeOH (2 and 3). Magnetic measurements for 1 and 2 revealed observable slow magnetic relaxation behavior with anisotropic energy barriers of 12.18 and 4.96 K, respectively, for SMMs and only the tail of the peaks in the out-of-phase susceptibility, χ″, was observed in complex 3. Comparing a series of NP coligands, we could easily study the correlation between the directions of the anisotropic axes and magnetic properties for this trinuclear SMM system.

Slow magnetic relaxation in a Dy3 triangle and a bistriangular Dy6 cluster

“…Such an observation is not unusual owing to the existence of different Dy III centres in the system, as those observed in other polynuclear lanthanide SMMs. 61–63…”

“…Such an observation is not unusual owing to the existence of different Dy III centres in the system, as those observed in other polynuclear lanthanide SMMs. [61][62][63] Two series of relaxation times τ and α parameters were obtained by fitting the frequency-dependent signals based on the sum of two modified Debye functions, as indicated in eq. 1.…”

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

“…35−38 The Layfield group obtained an SMM presenting the highest reported energy barrier (1837 K) and blocking temperature (60 K) at that time by the use of 1,2,4tri(tertbutyl)cyclopentadienyl ligand for the enhancing magnetic anisotropy of Dy 3+ in combination with the removal of equatorial ligands. 35 The influences of different terminal solvent ligands 36 and substitutions on ligands 37 as well as the steric hindrance and charge-driving effects of ligands 38 on SMM performances were also investigated. It is believed that the ligands play their roles through tuning the type and strength of ligand fields for metal ions and also through tuning the topologies.…”

“…The selection of appropriate ligands can help to achieve this goal not only by tuning the nature for the targeted lanthanide SMMs also including their easy axes but also by promoting the magnetic interactions between lanthanide ions. − Up to now, a deep insight into the role of ligand in optimizing the performance of SMMs has been on the way. − The Layfield group obtained an SMM presenting the highest reported energy barrier (1837 K) and blocking temperature (60 K) at that time by the use of 1,2,4-tri­(tertbutyl)­cyclopentadienyl ligand for the enhancing magnetic anisotropy of Dy 3+ in combination with the removal of equatorial ligands . The influences of different terminal solvent ligands and substitutions on ligands as well as the steric hindrance and charge-driving effects of ligands on SMM performances were also investigated. It is believed that the ligands play their roles through tuning the type and strength of ligand fields for metal ions and also through tuning the topologies.…”

Two-Dimensional Excitonic Metal–Organic Framework: Design, Synthesis, Regulation, and Properties

“…How to effectively manipulate the synthesis of a specific structure to get target MOFs with specific properties is an enormous challenge, although their structures are diversified owing to the diversity of organic ligands. At present, numerous researchers are focused on the directional design and preparation of complexes with certain properties. − The direct synthesis of complexes with different structures by using the substituent effect is an effective method widely used for the regulation of the structures of complexes. − More importantly, the properties of the substance change as the structure changes; thus, it is easy to achieve regulation of complex properties at the molecular level by transformation of the substituents. − …”