n-Hua Jia

A Stable Pentagonal Bipyramidal Dy(III) Single-Ion Magnet with a Record Magnetization Reversal Barrier over 1000 K

Single-molecule magnets (SMMs) with a large spin reversal barrier have been recognized to exhibit slow magnetic relaxation that can lead to a magnetic hysteresis loop. Synthesis of highly stable SMMs with both large energy barriers and significantly slow relaxation times is challenging. Here, we report two highly stable and neutral Dy(III) classical coordination compounds with pentagonal bipyramidal local geometry that exhibit SMM behavior. Weak intermolecular interactions in the undiluted single crystals are first observed for mononuclear lanthanide SMMs by micro-SQUID measurements. The investigation of magnetic relaxation reveals the thermally activated quantum tunneling of magnetization through the third excited Kramers doublet, owing to the increased axial magnetic anisotropy and weaker transverse magnetic anisotropy. As a result, pronounced magnetic hysteresis loops up to 14 K are observed, and the effective energy barrier (Ueff = 1025 K) for relaxation of magnetization reached a breakthrough among the SMMs.

Multifunctional DyIII4 Cluster Exhibiting White‐Emitting, Ferroelectric and Single‐Molecule Magnet Behavior

Significant attention has been paid to the investigation of single-molecule magnets (SMMs) since the first Mn12 cluster with such properties was reported in 1993. During the past two decades, SMMs have experienced three generations of development, from the initially studied 3d metal clusters to mixed 3d–4f clusters, and now to 4f-based species. The drastically increased interest in 4f-based SMMs is because of their significant magnetic anisotropy originating from large unquenched orbital angular momenta. On the other hand, lanthanide-based complexes are also the subject of intense investigation as luminescent materials as a result of their large Stokes shifts and the very narrow emission bands observed. Recently, some pioneering studies have combined both properties to improve the performance and enlarge the application scope. A few Dy and Yb complexes have recently been shown to be luminescent SMMs. To further miniaturize molecule-based devices, multifunctional SMMs combining versatile physical properties, such as ferroelectricity, dielectricity, and chirality may be useful. The large inherent anisotropy of the Dy ion has made it an ideal candidate for the manufacture of a series of SMMs. Additionally, Dy can function as a yellow-light emitter. The combination of a yellow-emitting Dy unit and a blueemitting organic chromophore will result in dual-color Y/B emission from a single molecule that can be used to generate white-light emission. At the same time, the blue-lightemitting ligand (Figure S1 in the Supporting Information), 3,5-bis(pyridin-2-yl)-1,2,4-trizole (Hbpt), exhibits potential chirality because of the presence of torsion angles between aromatic rings, which may lead to a chiral structure from the Dy–Hbpt reaction system. Following the above-designed strategy, solvothermal reactions of DyACHTUNGTRENNUNG(NO3)3, Hbpt, and NEt3 have been carried out in different solvents. Luckily, colorless block-shaped crystals of chiral complex 1 (D-1 and L-1 are the two enantiomers), [Dy4ACHTUNGTRENNUNG(m-bpt)4ACHTUNGTRENNUNG(m3-OH)2ACHTUNGTRENNUNG(m-OMe)2ACHTUNGTRENNUNG(NO3)4]·3 MeOH, were obtained from a solution in methanol at 120 8C, which are very different from those obtained from solutions in ethanol. The phase purity of bulk 1 was confirmed by comparison of its powder diffraction pattern with that calculated from the single crystal study (Figure S2 in the Supporting Information). Single-crystal X-ray structure analysis reveals that complex 1 crystallizes in the monoclinic space group P21. The molecular structures are depicted in Figure 1 and show that all Dy ions possess distorted square-antiprismatic geometries with N4O4 coordination environments (Figure S3 in the

A zigzag DyIII4 cluster exhibiting single-molecule magnet, ferroelectric and white-light emitting properties

A novel multifunctional complex [Dy4(OH)2(bpt)4(NO3)6(EtOH)2]·EtOH (1, Hbpt = 3,5-bis(pyridin-2-yl)-1,2,4-trizolate) was designed, based on the self-assembly under hydrothermal conditions, and it displays properties of single-molecule magnets (SMMs), white-light emission and ferroelectricity. Studies of static and dynamic magnetism reveal the SMMs behaviour of 1 with energy barrier Ueff = 43.22(8) K. Furthermore, the strategy of a dichromatic mixture of blue (bpt−) and yellow (Dy3+) emissive colours was utilized to obtain white-light emission through modulation of the excitation wavelength. This strategy has been worked up to create lanthanide-based fluorescent molecular magnets recently. Moreover, ferroelectricity, a “plus” feature, was added to the cluster as a result of the polar point group C2v.

Desolvation-Driven 100-Fold Slow-down of Tunneling Relaxation Rate in Co(II)-Dy(III) Single-Molecule Magnets through a Single-Crystal-to-Single-Crystal Process.

Single-molecule magnets (SMMs) are regarded as a class of promising materials for spintronic and ultrahigh-density storage devices. Tuning the magnetic dynamics of single-molecule magnets is a crucial challenge for chemists. Lanthanide ions are not only highly magnetically anisotropic but also highly sensitive to the changes in the coordination environments. We developed a feasible approach to understand parts of the magneto-structure correlations and propose to regulate the relaxation behaviors via rational design. A series of Co(II)-Dy(III)-Co(II) complexes were obtained using in situ synthesis; in this system of complexes, the relaxation dynamics can be greatly improved, accompanied with desolvation, via single-crystal to single-crystal transformation. The effective energy barrier can be increased from 293 cm−1 (422 K) to 416 cm−1 (600 K), and the tunneling relaxation time can be grown from 8.5 × 10−4 s to 7.4 × 10−2 s. These remarkable improvements are due to the change in the coordination environments of Dy(III) and Co(II). Ab initio calculations were performed to better understand the magnetic dynamics.

A brilliant cryogenic magnetic coolant: magnetic and magnetocaloric study of ferromagnetically coupled GdF3

The use of paramagnetic molecules as cryogenic coolants usually requires relatively large fields to obtain a practical cooling effect. Thus, research into magnetic molecular materials with larger MCEs in fields of ≤2 T is the main focus in this area. In this work, the crystal structure, magnetic susceptibility and isothermal magnetization for the inorganic framework material GdF3 were measured, and the isothermal entropy change was evaluated up to 9 T. Thanks to the combination of the large isotropic spin of Gd3+, the dense structure and weak ferromagnetic interaction, an extremely large −ΔSm for GdF3 was observed up to 528 mJ cm−3 K−1 for Δμ0H = 9 T, proving it to be an exceptional cryogenic magnetic coolant.

Dynamic Magnetic and Optical Insight into a High Performance Pentagonal Bipyramidal DyIII Single-Ion Magnet

The pentagonal bipyramidal single-ion magnets (SIMs) are among the most attractive prototypes of high-performance single-molecule magnets (SMMs). Here, a fluorescence-active phosphine oxide ligand CyPh2 PO (=cyclohexyl(diphenyl)phosphine oxide) was introduced into [Dy(CyPh2 PO)2 (H2 O)5 ]Br3 ⋅2 (CyPh2 PO)⋅EtOH⋅3 H2 O, and combined dynamic magnetic measurement, optical characterization, ab initio calculation, and magneto-optical correlation of this high-performance pseudo-D5h DyIII SIM with large Ueff (508(2) K) and high magnetic hysteresis temperature (19 K) were performed. This work provides a deeper insight into the rational design of promising molecular magnets.

Single-Molecule-Magnet Behavior in a [2 × 2] Grid DyIII4 Cluster and a Dysprosium-Doped YIII4 Cluster

Thanks to the MeCN hydrolysis in situ reaction, a [2 × 2] square grid Dy(III)4 cluster based on a polypyridyl triazolate ligand, [Dy4(OH)2(bpt)4(NO3)4(OAc)2] (1), was separated successfully and characterized through single-crystal X-ray diffraction and SQUID magnetometry. The frequency-dependent signals in the out-of-phase component of the susceptibility associated with slow relaxation of the magnetization confirmed that complex 1 displays single-molecule magnet (SMM) behavior. Two distinct slow magnetic relaxation processes, with effective energy barriers Ueff1 = 93 cm(-1) for fast relaxation and Ueff2 = 143 cm(-1) for slow relaxation observed under a zero direct-current field, are mainly attributed to the origin of single-ion behavior, which can be further acknowledged by the magnetic investigation of a dysprosium-doped yttrium cluster. Besides, it should be noted that complex 1 represents so far the highest energy barrier among the pure Dy(III)4 SMMs.

Lanthanide oxide clusters: from tetrahedral [Dy4(μ4-O)](10+) to supertetrahedral [Ln20(μ4-O)11]38+ (Ln = Tb, Dy, Ho, Er).

Supertetrahedral clusters: A family of lanthanide oxide supertetrahedral T3{Ln20} clusters (Ln = Tb, Dy, Ho, Er; see figure) were obtained from the solvothermal reaction of lanthanide(III) salts with polytriazolate ligands that could be methylated and oxidized in situ.

Unprecedented hexagonal bipyramidal single-ion magnets based on metallacrowns

Two Ln(iii) (Ln = Ce or Nd) complexes based on [15-MC-6] (MC = metallacrown) and phosphine oxide are reported for the first time with the Ln(iii) ion featuring nearly perfect hexagonal bipyramidal LnO8 geometry, with pseudo-D6h symmetry. Magnetic measurements reveal that both behave as single-ion magnets (SIMs), where the slow relaxation is dominated by the Raman mechanism.

Modulation of single-molecule magnet behaviour via photochemical [2+2] cycloaddition

The first example of phototunable SMMs has been reported. Upon UV irradiation, variations of the coordination sphere around Dy(III) ions actually affect the magnetic behaviour of the compound via [2+2] cycloaddition reaction, leading to a magnetic transformation from the SMM behaviour to a field-induced slow relaxation.