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1.
Eight-coordinated DyIII centres with D6h symmetry are expected to act as high-performance single-molecule magnets (SMMs) due to the simultaneous fulfilment of magnetic axiality and a high coordination number (a requisite for air stability). But the experimental realization is challenging due to the requirement of six coordinating atoms in the equatorial plane of the hexagonal bipyramid; this is usually too crowded for the central DyIII ion. Here a hexaaza macrocyclic Schiff base ligand and finetuned axial alkoxide/phenol-type ligands are used to show that a family of hexagonal bipyramidal DyIII complexes can be isolated. Among them, three complexes possess nearly perfect D6h local symmetry. The highest effective magnetic reversal barrier is found at 1338(3) K and an open hysteresis temperature of 6 K at the field sweeping rate of 1.2 mT s−1; this represents a new record for D6h SMMs.  相似文献   
2.
Reaction of the Schiff base ligand H2L and dysprosium acetate result in a new planar Dy6 cluster [Dy63‐OH)L6(Ac)6] · MeOH ( 1 ) [H2L = N'‐(2‐hydroxybenzylidene)‐2‐(hydroxyimino)propanohydrazide, HAc = acetic acid], which was successfully structurally and magnetically characterized. Single‐crystal X‐ray diffraction analysis revealed that 1 contained a hexanuclear dysprosium cluster [Dy6], which is composed of four Dy3 triangular units. Magnetic measurements suggest that 1 displays single‐molecule magnet (SMM) behavior which is enhanced by applying a 4000 Oe direct‐current field. The effective anisotropic barrier Ueff/kB = 14.9 K and the pre‐exponential factor τ0 = 1.31 × 10–6 s are also obtained. This work may provide more insights for the design and investigation of lanthanide‐based SMMs.  相似文献   
3.
A new potassium dysprosium polyborate, K3DyB6O12, has been prepared via the high‐temperature molten salt method and structurally characterized by single‐crystal X‐ray diffraction analysis. The structure can be described as a three‐dimensional framework composed of isolated bicyclic [B5O10]5? groups and Dy3+ and K+ ions. The Fourier transform IR (FT–IR) and ultraviolet–visible (UV–Vis) spectra were investigated. A series of K3Gd1–xDyxB6O12 phosphors was prepared and their photoluminescence properties were studied. The K3Gd1–xDyxB6O12 phosphors exhibit a strong yellow emission band at 577 nm (the 4F9/26H13/2 transition of Dy3+) under UV excitation of 275 nm (the 8S7/26IJ transition of Gd3+), suggesting the occurrence of the energy transfer Gd3+→Dy3+. The optimized doping concentration of the Dy3+ ion was 8 mol%. We may expect that K3Gd1–xDyxB6O12 is a promising pale‐yellow emission phosphor for visual displays or solid‐state lighting.  相似文献   
4.
A giant tetrahedral heterometallic polyoxometalate (POM) [Dy30Co8Ge12W108O408(OH)42(OH2)30]56?, which shows single‐molecule magnet (SMM) behavior, is described. This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d–4f and 4f coordination cluster assemblies within same POM framework.  相似文献   
5.
The dicarbollide ion, nido-C2B9H112− is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C2B9H11)2Ln(THF)2][Na(THF)5] (Ln=Dy, 1Dy ) and [(THF)3(μ-H)3Li]2[{η5-C6H4(CH2)2C2B9H9}Dy{η25-C6H4(CH2)2C2B9H9}2Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central DyIII ion. The effective energy barrier (Ueff) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido-C2B9H112− and nido-[o-xylylene-C2B9H9]2−, which show a Ueff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C2B9H11)2] is predicted to have comparable properties with the linear [Dy(CpMe3)2]+ complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high-performance single-molecule magnets.  相似文献   
6.
The substitution of scandium in fullerene single-molecule magnets (SMMs) DySc2N@C80 and Dy2ScN@C80 by lutetium has been studied to explore the influence of the diamagnetic metal on the SMM performance of dysprosium nitride clusterfullerenes. The use of lutetium led to an improved SMM performance of DyLu2N@C80, which shows a higher blocking temperature of magnetization (TB=9.5 K), longer relaxation times, and broader hysteresis than DySc2N@C80 (TB=6.9 K). At the same time, Dy2LuN@C80 was found to have a similar blocking temperature of magnetization to Dy2ScN@C80 (TB=8 K), but substantially different interactions between the magnetic moments of the dysprosium ions in the Dy2MN clusters. Surprisingly, although the intramolecular dipolar interactions in Dy2LuN@C80 and Dy2ScN@C80 are of similar strength, the exchange interactions in Dy2LuN@C80 are close to zero. Analysis of the low-frequency molecular and lattice vibrations showed strong mixing of the lattice modes and endohedral cluster librations in k-space. This mixing simplifies the spin–lattice relaxation by conserving the momentum during the spin flip and helping to distribute the moment and energy further into the lattice.  相似文献   
7.
以N-(2-羟基-3-甲氧基亚苄基)氨基脲(H2hms)与不同取代基的羧酸(RCOOH)为配体,合成了3例席夫碱类的中心对称双核镝基配合物[Dy2(Hhms)2(C(CH3)3COO)2(H2O)4](NO3)2(1)、[Dy2(Hhms)2(C14H9COO)2(C2H5OH)2(CH3OH)2][ZnCl4](2)和[Dy2(Hhms)2(C6H3(NH2)2COO)2Cl2]·2CH3CN(3),并对其进行了结构和磁性表征。结构分析表明,配合物1和2保持了相似的单帽四方反棱柱配位构型,但1与2中羧酸与Dy(Ⅲ)键合的方式不同;配合物2和3保持了相似的酚氧和羧酸桥联结构,但由于配位小分子的不同,配合物3中Dy(Ⅲ)离子的配位几何构型与2有所不同。磁性测试结果表明,配合物3在零场下观察到显著的单分子磁体行为,具有磁翻转有效能垒96 K。相反,配合物1仅表现了快的量子隧穿弛豫行为,甚至配合物2没有单分子磁体的弛豫信号。借助结构特点和各向异性轴取向等关键信息,对3例配合物的磁构效关系进行了讨论。研究结果表明利用羧酸配体取代基能够实现对分子磁各向异性以及对称性的良好调控,从而提高镧系单分子磁体磁弛豫行为。  相似文献   
8.
In search of magneto‐optic materials, the mononuclear compounds LnIII(depma)(NO3)3(hmpa)2 (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365 nm without loss of crystallinity. The Dy compound switches from a single‐ion to a single‐molecule magnet with doubling of the spin reversal barrier energy and from yellow‐green to blue‐white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto‐optic property.  相似文献   
9.
以氮氧自由基为配体,合成了2例未见文献报道的氮氧自由基-稀土配合物[Dy(hfac)3(NIT-C3H5)(H2O)]与[Dy(hfac)3(NIT-C3H5)]n(hfac=六氟乙酰丙酮,NIT-C3H5=2-环丙烷基-4,4,5,5-四甲基-2-咪唑啉-3-氧化-1-氧基自由基)。单晶结构分析表明配合物1为单核结构,单斜晶系P21/c空间群;配合物2为一维结构,单斜晶系P21/c空间群。交流磁化率测试结果表明配合物2虚部表现出频率依赖,这表明配合物2是单链磁体。  相似文献   
10.
We report three structurally related single ion Dy compounds using the pentadentate ligand 2,6-bis((E)-1-(2-(pyridin-2-yl)-hydrazineylidene)ethyl)pyridine (H2dapp) [Dy(H2dapp)(NO3)2]NO3 ( 1 ), [Dy(H2dapp)(OAc)2]Cl ( 2 ) and [Dy(H2dapp)(NO3)2]Cl0.92(NO3)0.08 ( 3 ). The (H2dapp) occupies a helical twisted pentagonal equatorial arrangement with two anionic ligands in the axial positions. Further influence on the electronic and magnetic structure is provided by a closely associated counterion interacting with the central N−H group of the (H2dapp). The slow relaxation of the magnetisation shows that the anionic acetates give the greatest slowing down of the magnetisation reversal. Further influence on the relaxation properties of compounds 1 and 2 is the presence of short nitrate-nitrate intermolecular ligand contact opening further lattice relaxation pathways.  相似文献   
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