Synthesis and Photochemical Properties of Heterometallic Ti-Cu Ring Clusters Constructed from Myo-Inositol Ligand

Incorporating heterometals into titanium-oxygen clusters represents an effective approach to adjusting the band gap and absorption properties. Herein, a family of heterometallic Ti-Cu clusters was synthesized under solvothermal conditions. The unique structural feature of these clusters is the formation of ring clusters with myo-inositol ligands serving as structure-directing ligands. The myo-inositol ligand, as a typical polyol ligand, demonstrates flexible and distinctive coordination modes capable of chelating up to eight transition metal ions simultaneously. Compounds 4 and 5 show significant absorption in the visible region, indicating that the incorporation of Cu ions can efficiently tune the band gap of titanium-oxygen clusters.

Double-Propeller-like Heterometallic 3d-4f Clusters Ln18Co7

Two high-nuclearity lanthanide-transition metal clusters with the general formula [Ln₁₈Co^IICo^III₆(OH)₁₄(CO₃)₉(CH₃CH₂COO)₆(dea)₁₂(H₂O)₃₀]·(NO₃)₈·Cl₄·(CH₃CH₂OH)₆·(H₂O)₁₂ (Ln₁₈Co₇, Ln = Gd (1) and Dy (2)) have been obtained by reacting CoCl₂·6H₂O, Ln(NO₃)₃·6H₂O, and a mixture of ligands consisting of propionate and diethanolamine (H₂dea). Crystal structural analysis exhibits two three-blade propellers composed of the Co^III₃Ln₉ units connected by one Co^II ion and three CO₃^2- ions, which assemble into a double-propeller-like structure (Ln₁₈Co^IICo^III₆). Magnetocaloric effect (MCE) studies indicate that Gd₁₈Co₇ exhibits a large entropy change (-ΔS_m) of 36.9 J kg^-1 K^-1.

A 2D layer network assembled from an open dendritic silver cluster Cl@Ag11N24 and an N-donor ligand

A 2D layer network was synthesized from an N-donor ligand and a new silver cluster featuring an open dendritic structure with a high coordination ratio of N atom. Both the assembly process and luminescence properties of this complex was studied.

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

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 CO₂ 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_M) and magnetic density, and the intracluster antiferromagnetic exchange coupling. We have also made some preliminary attempts at preparing processable and practically useful materials in the form of a monodisperse core-shell nanostructure. We succeeded in encapsulating a single nanosized heterometallic molecular cluster in a nanoshell of silica. It was found that such passivation not only helped stabilize the cluster but also reduced the magnetic interactions between individual clusters. These effects are reflected in the slightly enhanced value of -ΔS_M for the core-shell composite over the parent unprotected cluster.

Isolation, structure and magnetic properties of two novel core-shell 3d-4f heterometallic nanoscale clusters

Two novel core-shell Ni-Ln nanosized clusters, Na₄(H₃O)₄[Nd₃₈Ni_42.5(IDA)₄₂(OAc)₄(CH₃CH₂OH)₂(CO₃)₁₈(μ₃-OH)₆₂(μ₃-O)₆(H₂O)₁₂]Cl₆·26H₂O (1) and Na[Pr₄₂Ni₃₈(μ₃-OH)₇₁(μ₃-O)₄(IDA)₃₈(NH₂CH₂COO)₂(OAc)₂(CH₃CH₂OH)₂(CO₃)₁₆(H₂O)₆Cl₇]Cl₃·37H₂O (2) (IDA = iminodiacetate), were successfully prepared using the Cl^- anion and the flexible ligand iminodiacetic acid. Structural analysis indicates that the discrete dumbbell-shaped 3d-4f heterometallic cluster in 1 is constructed from two {Nd₁₉Ni₂₁} clusters connected by one {NiO₆} unit, whereas the bowknot-shaped nanosized cluster is composed of two {Pr₁₉Ni₁₉} clusters ligated by two {Pr₂} units and CO₃^2- anions. The formation of both compounds indicates that Cl^- ions play important roles and act not only as balance anions but also as template and bridging ligands. The magnetic properties of compounds 1 and 2 were investigated, and it was revealed that they display dominant antiferromagnetic exchange.

Two nanosized 3d–4f clusters featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron

Two high-nuclearity 3d–4f clusters Ln₂₄Zn₄ (Ln = Gd and Sm) featuring four Ln₆ octahedra encapsulating a Zn₄ tetrahedron were obtained through the self-assembly of Zn(OAc)₂ and Ln(ClO₄)₃.

Nanoscopic molecular magnets

This review highlights fundamental concepts and synthetic strategies of SMMs and selected examples of 3d, 4f, 5f and mixed 3d–4f, 4d–5d and 3d–5f based SMMs are discussed.