Synthesis and Structures of Lanthanide–Transition Metal Clusters

Zheng, Xiu‐Ying; Kong, Xiang‐Jian; Liu, Long

doi:10.1007/430_2016_6

Cited by 16 publications

(17 citation statements)

References 239 publications

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“…There are only a few cases of Ln–Cr clusters with high-nuclearity (>10 core) reported to date. ,, An effective synthesis to form high-nuclearity Ln–Cr metal clusters has not been developed due to the extremely high kinetic inertia. Research has shown that ligand-controlled metal hydrolysis and anion template approaches are universal strategies for the synthesis of high-nuclearity 3d–4f metal clusters . It is important to choose suitable ligands for the ligand-controlled hydrolytic approach .…”

Section: Introductionmentioning

confidence: 99%

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

et al. 2020

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A series of heterometallic Ln–Cr clusters with the formulas [Ln5Cr2(H2L)2(OAc)6(μ3-OH)6(H2O)15](ClO4)7·xH2O (Ln = Gd and x = 33 for 1 and Ln = Dy and x = 21 for 2) and [Ln8Cr4(H2L)4(OAc)8(μ3-OH)16(μ4-O)1(H2O)8](Cl)(ClO4)5·10H2O (Ln = Gd for 3 and Ln = Dy for 4) was obtained through the reaction of the acetate ligands 2,2-dimethylolpropionic acid (H3L) and Ln(ClO4)3 in the presence of chromium salts with different anions under the same high pH conditions. X-ray analysis revealed that compound 1 contained a metal unit [Gd3Cr2] displaying the pentagonal bipyramid configuration and that compound 3 was templated by Cl– and ClO4 – as a mixed anion template featuring a quadrangular structure. In compound 3, the 12 metal atoms were arranged in a wheel-shaped metal skeleton [Gd8Cr4], which was produced by 4 tetrahedral metal units [Gd3Cr] sharing vertices. The introduction of the mixed anion template increased the number of metal atoms in the Ln–Cr clusters. Magnetic calculations indicated that there was weak antiferromagnetic Gd···Cr coupling and weak ferromagnetic Gd···Gd coupling in 1, whereas both Gd···Cr and Gd···Gd in 3 exhibited weak antiferromagnetic interactions. Magnetothermal studies showed that compounds 1 and 3 displayed magnetic entropy changes of 25.2 J kg–1 K–1 at 5 K and 7 T and 33.8 J kg–1 K–1 at 2 K and 7 T, respectively.

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Section: Introductionmentioning

confidence: 99%

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

et al. 2020

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“…Among them, chiral molecular clusters play a significant role in many fields as biological, chemical, and material sciences. , For example, the magneto-chiral dichroism effect in chiral paramagnetic complexes has driven researchers to prepare multifunctional molecular materials both containing chirality and magnetism . Compared with the reported series of giant 3 d -4 f metal clusters, there are very few studies on the high-nuclearity chiral 3 d -4 f metal clusters due to the difficulty in synthesis . Under the premise of introducing chiral elements, it is a great challenge to increase the number of metallic cores of 3 d -4 f clusters on account of the different coordination geometry of 3 d and 4 f metal ions.…”

Section: Introductionmentioning

confidence: 99%

High-Nuclearity Chiral 3d-4f Heterometallic Clusters Ln₆Cu₂₄ and Ln₆Cu₁₂

et al. 2019

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Based on the anion template and chiral ligand inducting role, two series of high-nuclearity 3d-4f heterometallic clusters with formulas [NO3@Ln6Cu24(μ3-OH)30(μ2-OH)3(OAc)6(R/S-L)12(H2O)24](NO3)14·x(H2O) (Ln = Dy, x = 30 for 1a(R-L) and 1b(S-L); Ln = Tb, x = 40 for 2a(R-L) and 2b(S-L)) and (Et3NH)4[Ln6Cu12(μ3-OH)14(μ2-Cl)6Cl12(R/S-L)12]Cl2·x(H2O) (Ln = Dy, x = 28 for 3a(R-L) and 3b(S-L); Ln = Tb, x = 33 for 4a (R-L) and 4b(S-L); HL = (R/S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), have been synthesized and characterized. Structural analysis reveals that the metal skeleton of compounds 1 and 2 display a Ln6Cu12 octahedral inner core encapsulated by six outer Cu2 units. In the Ln6Cu12 octahedron, 6 Ln3+ ions located at the six vertices and 12 inner Cu2+ ions located at the 12 edges of octahedron, and one NO3 – locates in the center of the octahedron. The metal core of compounds 3 and 4 can be viewed as a Ln6 octahedron encapsulated by six Cu2 units. It is interesting that the different inorganic anions involved in the reaction result in the difference in the structures of 1 to 2 and 3 to 4. Circular dichroism spectra of 1–4 display obvious mirror symmetry effect at 600–800 nm of d–d transition of Cu2+, suggesting that the chirality transferred from chiral R- and S-ligand to Cu2+ ions in this system. Notably, the CD peak at the Cu2+ d–d transition position of Ln6Cu12 cluster is obviously blue-shifted compared with that of Ln6Cu24 due to the different coordinated environments of Cu2+. Magnetic studies indicate that 1a and 2a show weak ferromagnetic interactions, while 3a and 4a display antiferromagnetic interactions.

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“…These include the nature of the hydrolysis-limiting ligands, the ligand/metal ratio, possible involvement of anion templates, pH, temperature, and duration. 18 Despite the efforts made and progress achieved, the number of giant clusters (nuclearity >25) remains small. 19 According to the structural characteristics of a representative cluster (Figure 2), we focused our synthetic strategy on the slow and templated buildup of the cluster core.…”

Section: Strategy For the Synthesis Of High-nuclearity Lanthanide-con...mentioning

confidence: 99%

High-Nuclearity Lanthanide-Containing Clusters as Potential Molecular Magnetic Coolers

et al. 2018

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High-nuclearity cluster-type metal complexes are a unique class of compounds, many of which have aesthetically pleasing molecular structures. Their interesting physical and chemical properties arise primarily from the electronic and/or magnetic interplay between the component metal ions. Among the extensive studies in the past two decades, those on lanthanide-containing clusters, lanthanide-exclusive or heterometallic with transition metal elements, are most notable. The research was driven by both the synthetic challenges for these generally elusive species and their intriguing magnetic properties, which are useful for the development of energy-efficient and environmentally friendly magnetic cooling technologies. Our efforts in this vein have been concentrated on developing rational synthetic methods for high-nuclearity lanthanide-containing clusters. By means of the now widely adopted approach of "ligand-controlled hydrolysis" of lanthanide ions, a great variety of cluster-type lanthanide hydroxide complexes had been prepared in the first half of this developing period (1999-2006). In this Account, our efforts since 2007 are summarized. These include (1) further development of synthetic strategies in order to expand the ligand scope and/or to increase the nuclearity (>25) of the cluster species and (2) magnetic studies pertinent to the pursuit of materials with a large magnetocaloric effect (MCE). Specifically, with the hope of expanding the family of ligands and producing clusters of previously unknown structures, we tested under hydrothermal or solvothermal conditions the use of readily available yet not commonly used ligands for controlling lanthanide hydrolysis; such ligands, carboxylates as mundane examples, tend to form insoluble complexes prior to any possible hydrolysis. We have also validated the use of preformed transition metal complexes as metalloligands for subsequent control of lanthanide hydrolysis toward heterometallic 3d-4f clusters. Furthermore, we demonstrated using ample examples that the presence of small anions as templates is essential to the assembly of high-nuclearity lanthanide-containing clusters and that maintaining a low concentration of the anion template(s) is a key to such success. It has been found that slow production/release of such anion templates by in situ ligand decomposition or absorption of atmospheric CO is effective in preventing precipitation of their lanthanide salts, allowing not only controllable lanthanide hydrolysis but also gradual and modular assembly of the giant cluster species. Magnetic studies targeting potential applications of such clusters as molecular magnetic coolers have also been conducted. The results are summarized in the second portion of this Account in an effort to establish a certain magneto-structure relationship. Of particular relevance is the possible correlation between MCE (evaluated using the isothermal magnetic entropy change, -ΔS) and magnetic density, and the intracluster antiferromagnetic exchange coupling. We have also made some prel...

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Synthesis and Structures of Lanthanide–Transition Metal Clusters

Cited by 16 publications

References 239 publications

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

High-Nuclearity Chiral 3d-4f Heterometallic Clusters Ln₆Cu₂₄ and Ln₆Cu₁₂

High-Nuclearity Lanthanide-Containing Clusters as Potential Molecular Magnetic Coolers

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Synthesis and Structures of Lanthanide–Transition Metal Clusters

Cited by 16 publications

References 239 publications

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln5Cr2 and Ln8Cr4

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln5Cr2 and Ln8Cr4

High-Nuclearity Chiral 3d-4f Heterometallic Clusters Ln6Cu24 and Ln6Cu12

High-Nuclearity Lanthanide-Containing Clusters as Potential Molecular Magnetic Coolers

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Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln₅Cr₂ and Ln₈Cr₄

High-Nuclearity Chiral 3d-4f Heterometallic Clusters Ln₆Cu₂₄ and Ln₆Cu₁₂