Incorporation of Silicon–Oxygen Tetrahedron into Novel High-Nuclearity Nanosized 3d–4f Heterometallic Clusters

A Cubic Tinkertoy-like Heterometallic Cluster with a Record Magnetocaloric Effect

Clusters showing a giant magnetocaloric effect (MCE) are of interest as molecular coolants for magnetic refrigeration. Herein, we report two heterometallic clusters, denoted as Gd152Ni14@Cl24 and Sm152Ni8, just to highlight their inorganic core motifs, obtained by ligand-controlled co-hydrolysis of Ni2+ and Ln3+ (Ln = Gd, Sm) in the presence of N-(2-hydroxyethyl)iminodiacetic acid (H2HEIDA). Both clusters display fascinating cubic Tinkertoy-like structures, with the core motifs being built of multiple metallic shells of Platonic and Archimedean polyhedra. The isothermal magnetic entropy change─a direct measurement of MCE─was determined to be 52.65 J·kg-1·K-1 at 2.5 K and 7.0 T for the Gd-containing cluster; this value is the highest known for any molecular clusters so far reported.

Exploration and Insights on Topology Adjustment of Giant Heterometallic Cages Featuring Inorganic Skeletons Assisted by Machine Learning

Inorganic molecular cages are emerging multifunctional molecular-based platforms with the unique merits of rigid skeletons and inherited properties from constituent metal ions. However, the sensitive coordination bonds and vast synthetic space have limited their systematic exploration. Herein, two giant cage-like clusters featuring the organic ligand-directed inorganic skeletons of Ni4[La74Ni104(IDA)96(OH)184(C2O4)12(H2O)76]·(NO3)38·(H2O)120 (La74Ni104, 5 × 5 × 3 - C2O4) and [La84Ni132(IDA)108(OH)168(C2O4)24(NO3)12(H2O)116]·(NO3)72·(H2O)296 (La84Ni132, 5 × 5 × 5 - C2O4) were discovered by a high-throughput synthetic search. With the assistance of machine learning analysis of the experimental data, phase diagrams of the two clusters in a four-parameter synthetic space were depicted. The effect of alkali, oxalate, and other parameters on the formation of clusters and the mechanism regulating the size of two n × m × l clusters were elucidated. This work uses high-throughput synthesis and machine learning methods to improve the efficiency of 3d-4f cluster discovery and finds the highest-nuclearity 3d-4f cluster to date by regulating the size of the n × m × l inorganic cages through oxalate ions, which pushes the synthetic methodology study on elusive inorganic giant cages in a significantly systematic way.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

Two SiO44--Templated Ln23Ni20 Clusters with Magnetic Cooling and Stability

Assembling and studying high-nuclearity 3d-4f metal clusters represent a pregnant and challenging research hotspot. Based on anionic template and ligand-controlled hydrolytic methods, two heterometallic metal clusters, formulated as [Gd₂₃Ni₂₀(DTA)₂₀(CO₃)₄(CH₃COO)₆(SiO₄)₄(CH₃CH₂OH)₂(μ₃-OH)₃₃(μ₂-OH)₄(H₂O)₁₆]·Cl₂·30H₂O and [Eu₂₃Ni₂₀(DTA)₂₀(CO₃)₄(CH₃COO)₆(SiO₄)₄(CH₃CH₂OH)₂(μ₃-OH)₃₃(μ₂-OH)₄(H₂O)₁₆]·Cl₂·46H₂O (abbreviated as Gd₂₃Ni₂₀, Eu₂₃Ni₂₀, H₂DTA = thiodiglycolic acid), are successfully obtained, which both feature similar double-shell-shaped structures with a Ni₂₀ building unit encapsulating a Ln₂₃ aggregation. The structural analysis illustrates that the SiO₄^4- anion, serving as the anionic template in this work, is reported for the second time in 3d-4f metal clusters. In terms of the magnetic properties, large amounts of Gd³⁺ and Ni²⁺ ions contribute to the MCE of compound Gd₂₃Ni₂₀, along with 38.15 J kg^-1 K^-1 at ΔH = 7.0 T for 2.0 K. It is worth mentioning that compound Gd₂₃Ni₂₀ exhibits an excellent magnetic entropy change at low fields (-ΔS_m = 19.10 J kg^-1 K^-1 at 2.0 K for ΔH = 2.0 T). In addition, Gd₂₃Ni₂₀ exhibits preferable solvent and thermal stability.

Efficiently increasing low-field magnetic entropy by incorporating SO32− into Gd22Ni21 clusters

One distinct nanosized cluster, Gd22Ni21, was isolated by the mixed-anion-templates (SO32- and SO42-), which was firstly reported in 3d-4f metal clusters. Additionally, Gd22Ni21 shows the largest low-field magnetic entropy change...

Pentagram-type Ln15 (Ln = Dy, Tb, Eu, Sm, Ho) clusters with different anion templates: magnetic and luminescence properties

Five pentagram-type Ln15 clusters with different anion templates were obtained. The pentagonal skeleton is composed of five cubane-like [Ln4(μ3-OH)4] building units. The magnetic properties and the luminescence behavior were investigated.

Structural Chemistry of Giant Metal Based Supramolecules

The review presents a bird-eye view on the state of research in the field of giant nonbiological discrete metal complexes and ions of nanometer size, which are structurally characterized by means of single-crystal X-ray diffraction, using the crystal structure as a common key feature. The discussion is focused on the main structural features of the metal clusters, the clusters containing compact metal oxide/hydroxide/chalcogenide core, ligand-based metal-organic cages, and supramolecules as well as on the aspects related to the packing of the molecules or ions in the crystal and the methodological aspects of the single-crystal neutron and X-ray diffraction of these compounds.

A High-Symmetry Double-Shell Gd30Co12 Cluster Exhibiting a Large Magnetocaloric Effect

A high-nuclearity 3d-4f cluster of [Gd₃₀Co^II₆Co^III₆(OH)₅₆(NO₃)₁₂(CH₃COO)₃₀(H₂O)₃₀]·(NO₃)₂₂·(en)₃·(H₂O)₃ (1) was synthesized through the reaction of Gd(NO₃)₃·6H₂O, Co(NO₃)₂·6H₂O, and sodium acetate in a mixture of ethanediamine (en), ethanol, and deionized water. The cluster core in 1 features a double-shell structure with a Co₁₂ icosahedron encapsulating a Gd₃₀ icosidodecahedron. A magnetic study reveals that separating Co²⁺ ions with Gd³⁺ ions can effectively reduce the magnetic interaction of 3d-4f clusters. Significantly, the magnetocaloric effect (MCE) of 1 at 2 K and 7 T is up to 44.7 J kg^-1 K^-1, the largest MCE reported to date in the 3d-4f metal clusters.

Structure, assembly mechanism and magnetic properties of heterometallic dodecanuclear nanoclusters DyIII4MII8 (M = Ni, Co)

Two isostructural heterometallic dodecanuclear nanoclusters [Dy4Co8(μ3-OH)8(L)8(OAc)4(H2O)4]·3EtOH·3CH3CN·H2O (1) and [Dy4Ni8(μ3-OH)8(L)8(OAc)4(H2O)4]·3.5EtOH·0.5CH3CN·5H2O (2) with different assembly mechanisms are presented here.

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

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.

Doubly interpenetrated indium-tricarboxylate frameworks mediated by small molecules with enhanced porosity

A synthetic strategy of indium-tricarboxylate frameworks by using small molecule regulators has been proposed to obtain four types of In-based coordination polymers with doubly interpenetrated structures.

Triethylamine-templated nanocalix Ln12 clusters of diacylhydrazone: crystal structures and magnetic properties

Three {Ln₁₂} (Ln = Gd (1), Tb (2), Dy (3)) nanocalix clusters with a novel ligand of N,N′-bis(o-vanillidene)-1H-imidazole-4,5-dicarbohydrazide (H₅ovih) were synthesized via the amine-templating strategy.