Chlorine-Induced Assembly of a Cationic Coordination Cage with a μ5-Carbonato-Bridged MnII24 Core

Three in One: Three Different Molybdates Trapped in a Thiacalix[4]arene Protected Ag72 Nanocluster for Structural Transformation and Photothermal Conversion

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO4 2- , Mo6 O22 8- and Mo7 O25 8- ) in situ transformed from classic Lindqvist Mo6 O19 2- , providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post-reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post-synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom-precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown.

Thiacalix[4]arene-Protected Silver Nanoclusters Encapsulating Different Two-Electron Superatom Oligomers

The subvalent silver kernel represents the nascent state of silver cluster formation, yet the growth mechanism has long been elusive. Herein, two silver nanoclusters (Ag30 and Ag34) coprotected by TC4A4- (H4TC4A = p-tert-butylthiacalix[4]arene) and TBPMT- (TBPMTH = 4-tert-butylbenzenemethanethiol) containing 6e and 4e silver kernels are synthesized and characterized. The trimer of the 2e superatom Ag14 kernel in Ag30 is built from a central Ag6 octahedron sandwiched by two orthogonally oriented Ag5 trigonal bipyramids through sharing vertexes, whereas a double-octahedral Ag10 kernel in Ag34 is a dimer of 2e superatoms. They manifest disparate polyhedron fusion growth patterns at the beginning of the silver cluster formation. Their excellent solution stabilities are contributed by the multisite and multidentate coordination fashion of TC4A4- and the special valence electron structures. This work demonstrates the precise control of silver kernel growth by the solvent strategy and lays a foundation for silver nanocluster application in photothermal conversion.

Atomically accurate structural tailoring of thiacalix[4]arene-protected copper(II)-based metallamacrocycles

Accurate manipulation of ligands at specific sites in robust clusters is attractive but difficult, especially for those ligands that coordinate in intricate binding patterns. By linking the shuttlecock-like {Cu₄(μ₄-Cl)TC4A} motif and the phenylphosphate (PhPO₃^2-) ligand, we elaborately design and synthesize two Cu(II)-thiacalix[4]arene metallamacrocycles (MMCs), namely Cu₁₂L₃ and Cu₁₆L₄, which have regular triangular and quadrilateral topologies, respectively. While keeping the core intact, the Cl^- and PhPO₃^2- in those two MMCs, which coordinated in a μ₄-bridging fashion, can be accurately substituted with salicylate ligands. Theoretical calculations have been carried out to reveal the effect of ligand tailoring on the electronic structure of clusters. Structural regulation can affect the catalytic activity of these clusters, which has been verified by using the clusters as catalysts for selective sulfide oxidation.

An ultrastable Ti-based metallocalixarene nanocage cluster with photocatalytic amine oxidation activity

Polyhedral metallocalixarene nanocage clusters based on pure Ti(IV) ions are to our knowledge unknown hitherto. Herein we report the first Ti(IV)-based metallocalixarene nanocage cluster by assembling a [Ti₁₃O₁₄] cage with six t-butylcalix[4]arene molecules. Notably, the cluster exhibits extraordinary stability in high-concentration acid/alkali solutions and can act as a stable photocatalyst to catalyze the oxidation of ammonia to imines.

Stepwise Assembly of Ag42 Nanocalices Based on a MoVI-Anchored Thiacalix[4]arene Metalloligand

Metalloligand strategy has been well recognized in the syntheses of heterometallic coordination polymers; however, such a strategy used in the assembly of silver nanoclusters is not broadly available. Herein, we report the stepwise syntheses of a family of halogen-templated Ag₄₂ nanoclusters (Ag42c-Ag42f) based on Mo^VI-anchored p-tert-butylthiacalix[4]arene (H₄TC4A) as a metalloligand (hereafter named MoO₃-TC4A). X-ray crystallography demonstrates that they are similar C₃-symmetric silver-organic nanocalices capped by six MoO₃-TC4A metalloligands, which are evenly distributed up and down the base of 42 silver atoms. These nanoclusters can be disassembled to six bowl-shaped [Ag₁₁(MoO₃-TC4A)(RS)₃] secondary building units (SBUs, R = Et or ⁿPr), which are fused together in a face-sharing fashion surrounding Cl^- or Br^- as a central anion template. The electrospray mass spectrometry (ESI-MS) indicates their high stabilities in solution and verifies the formation of the MoO₃-TC4A metalloligand, thereby rationalizing the overall stepwise assembly process for them. Moreover, Ag42c shows lower cytotoxicity and better activity against the HepG-2 cell line than MCF-7 and BGC-823. These results not only exemplify the effectiveness of a thiacalix[4]arene-based metalloligand in the assembly of silver nanoclusters but also give us profound insight about the step-by-step assembly process in silver nanoclusters.

A cyanometallate- and carbonate-bridged dysprosium chain complex with a pentadentate macrocyclic ligand: synthesis, structure, and magnetism

A novel one-dimensional polymeric cyanometallate- and carbonate-bridged dysprosium(iii) chain with a pentadentate macrocyclic ligand exhibits field-induced multiple-relaxation processes.

Constructing an unprecedented {MnII38} matryoshka doll with a [Mn18(CO3)9] inorganic core and magnetocaloric effect

An unprecedented inner [Mn₁₈(CO₃)₉] inorganic core and [Mn₂₀] metal-organic periphery compose a high-nuclearity homometallic single-valent {Mn^II₃₈} molecular aggregate with a [Mn₆] ⊂ [Mn₁₂] ⊂ [Mn₈] ⊂ [Mn₁₂] matryoshka doll-like skeleton that displays a significant magnetocaloric effect (MCE).

Coordination-Assembled Molecular Cages with Metal Cluster Nodes

Molecular cages have attracted great attention because of their fascinating topological structures and well-defined functional cavities. These discrete cages were usually fabricated by coordination assembly approach, a process employing directional metal-ligand coordination bonds due to the nature of the divinable coordination geometry and the required lability to encode dynamic equilibrium/error-correction. Compared to these coordination molecular cages with mononulcear metal-nodes, an increasing number of molecular cages featuring dinuclear and then polynuclear metal-cluster nodes have been synthesized. These metal-cluster-based coordination cages (MCCCs) combine the merits of both metal clusters and the cage structure, and exhibit excellent performances in catalysis, separation, host-guest chemistry and so on. In this review, we highlight the syntheses of MCCCs and their potential functions that is donated by the metal-cluster nodes.

Self-assembly of a nonanuclear NiII cluster via atmospheric CO2 fixation: synthesis, structure, collision-induced dissociation mass spectrometry and magnetic property

A novel nonanuclear nickel(ii) cluster identified as [Ni9(OH)6(CO3)2(ba)8(Hdmpz)6(DMF)2]·EtOH·2DMF (SD/Ni9a, Hba = benzoic acid, Hdmpz = 3,5-dimethyl-1H-pyrazole) is successfully constructed from mixed ligands. The single-crystal X-ray diffraction (SCXRD) structural analysis confirms the composition and reveals the "drum-like" inner core structure surrounded by ba- and DMF. Six Hdmpz ligands in their neutral form further sandwich the "drum" up and down, and is hydrogen bonded with two carbonate anions that are derived from the atmospheric CO2 with the help of Et3N. Electrospray ionization mass spectrometry (ESI-MS) reveals that the SD/Ni9a maintains an intact core in the solution with a slight exchange of outer ligands. Detailed collision-induced dissociation (CID) experiments reveal the collision energy (CE)-promoted ligand loss and exchange between ba- and Hdmpz. Furthermore, the magnetic study shows that there is no interaction between the Ni centers at room temperature, whereas the ferromagnetic coupling between the Ni centers is found with an S = 3 spin ground state of the cluster at low temperature. Moreover, the UV-vis spectrum and the photocurrent response measurements show its good optical properties with an indirect bandgap of about 2.35 eV and fast current response upon visible light irradiation.

A hierarchically assembled 88-nuclei silver-thiacalix[4]arene nanocluster

Thiacalix[4]arenes as a family of promising ligands have been widely used to construct polynuclear metal clusters, but scarcely employed in silver nanoclusters. Herein, an anion-templated Ag₈₈ nanocluster (SD/Ag88a) built from p-tert-butylthiacalix[4]arene (H₄TC4A) is reported. Single-crystal X-ray diffraction reveals that C₄-symmetric SD/Ag88a resembles a metal-organic super calix comprised of eight TC4A⁴⁻ as walls and 88 silver atoms as base, which can be deconstructed to eight [CrO₄@Ag₁₁(TC4A)(EtS)₄(OAc)] secondary building units arranged in an annulus encircling a CrO₄²⁻ in the center. Local and global anion template effects from chromates are individually manifested in SD/Ag88a. The solution stability and hierarchical assembly mechanism of SD/Ag88a are studied by using electrospray mass spectrometry. The Ag₈₈ nanocluster represents the highest nuclearity metal cluster capped by TC4A⁴⁻. This work not only exemplify the specific macrocyclic effects of TC4A⁴⁻ in the construction of silver nanocluster but also realize the shape heredity of TC4A⁴⁻ to overall silver super calix.

The assembly of giant silver clusters by using macrocylic multidentate ligand remains a challenge. Here, the authors synthesize a chromate-templated 88-nuclei silver super calix and reveal the role of anion templating effects and a hierarchical assembly mechanism.

Sodalite-like rare-earth carbonates: a study of structural transformation and diluted magnetism

A series of novel rare earth carbonates, RE3(OH)6(CO3)Cl (RE = Dy, Er, Y), with sodalite-like (SOD-like) zeolite topologies have been successfully synthesized by introducing an appropriate amount of CO3(2-) from NaCO3 or atmospheric carbon dioxide as a template. Single-crystal X-ray diffraction reveals that the structure consists of the RE3(OH)6(3+) cationic framework with a SOD-like topology built from vertex-sharing [RE4(μ3-OH)4] cubes. The CO3(2-) anions seal the 6-ring opening and Cl(-) anions situated in the channels to achieve charge balance. After calcination at 370 °C, the compound RE3(OH)6(CO3)Cl in situ transforms into a new phase formulated as RE3O4Cl. Interestingly, the structure of RE3O4Cl represents a new SOD-like open framework, associated with the removal of the CO3(2-) from RE3(OH)6(CO3)Cl. The samples are characterized by thermogravimetric analysis (TGA), elemental analysis, X-ray photoelectron spectroscopy and magnetic studies. Furthermore, single-molecule magnet behaviours can be observed for the diluted samples of Dy0.0068Y2.9932(OH)6(CO3)Cl and Dy0.0068Y2.9932O4Cl with a Dy/Y molar ratio of up to 1/440 as well as Er0.19Y2.81(OH)6(CO3)Cl with an Er/Y ratio of 1/15, showing dominant single-ion effects.

A new family of 1D, 2D and 3D frameworks aggregated from Ni5, Ni4 and Ni7 building units: synthesis, structure, and magnetism

Three polynuclear nickel(ii) complexes with 1D, 2D and 3D structures are controlled by carboxylate bridges of biphenyl-3,4′,5-tricarboxylic acid. Magnetic studies reveal that the polymers have ferromagnetic coupling features for 1 and 2 and an alternating magnetic chain behavior for 3.

Syntheses, structures, luminescence and magnetic properties of three high-nuclearity neodymium compounds based on mixed sulfonylcalix[4]arene-phosphonate ligands

The solvothermal reactions of p-tert-butylsulfonylcalix[4]arene (H₄BSC4A), phosphonic acid and neodymium chloride have resulted in three novel high-nuclearity neodymium coordination compounds.

Controllable coordination-driven self-assembly: from discrete metallocages to infinite cage-based frameworks

CONSPECTUS: Nanosized supramolecular metallocages have a unique self-assembly process that allows chemists to both understand and control it. In addition, well-defined cavities of such supramolecular aggregates have various attractive applications including storage, separation, catalysis, recognition, drug delivery, and many others. Coordination-driven self-assembly of nanosized supramolecular metallocages is a powerful methodology to construct supramolecular metallocages with considerable size and desirable shapes. In this Account, we summarize our recent research on controllable coordination-driven assembly of supramolecular metallocages and infinite cage-based frameworks. To this end, we have chosen flexible ligands that can adopt various conformations and metal ions with suitable coordination sites for the rational design and assembly of metal-organic supramolecular ensembles. This has resulted in various types of metallocages including M3L2, M6L8, M6L4, and M12L8 with different sizes and shapes. Because the kinds of metal geometries are limited, we have found that we can replace single metal ions with metal clusters to alternatively increase molecular diversity and complexity. There are two clear-cut merits of this strategy. First, metal clusters are much bigger than single metal ions, which helps in the construction and stabilization of large metallocages, especially nanosized cages. Second, metal clusters can generate diverse assembly modes that chemists could not synthesize with single metal ions. This allows us to obtain a series of unprecedented supramolecular metallocages. The large cavities and potential unsaturated coordination sites of these discrete supramolecular cages offer opportunities to construct infinite cage-based frameworks. This in turn can offer us a new avenue to understand self-assembly and realize certain various functionalities. We introduce two types of infinite cage-based frameworks here: cage-based coordination polymers and cage-based polycatenanes, which we can construct through coordination bonds and mechanical bonds, respectively. Through either directly linking the unsaturated coordination sites of metallocages or replacing the labile terminal ligands with bridging ligands, we can produce infinite cage-based frameworks based on coordination bonds. We introduce several interesting cage-based coordination polymers, including a single-crystal-to-single-crystal transformation from a M6L8 cage to an infinite cage-based chain. Compared with discrete metallocages, these kinds of materials can give us higher structural stability and complexity, favoring the applications of metallocages. In addition, we discuss how we can use mechanical bonds, such as interlocking and interpenetrating, to construct extended cage-based frameworks. So far, study in this field has focused on polycatenanes constructed from M6L4 and M12L8 cages, as well as a controllable and dynamic self-assembly based on M6L4 metallocages. We also discuss cage-based polycatenanes, which can give dynamic properties to discrete metallocages. We hope that our investigations will bring new insights to the world of the supramolecular metallocages by enlarging its breadth and encourage us to devote more effort to this blossoming field in the future.

Manganese–calcium clusters supported by calixarenes

An investigation inspired by the structure of the oxygen-evolving complex of photosystem II has resulted in the isolation and structural characterization of the first examples of Mn/Ca clusters supported by a calixarene ligand.

New coordination features; a bridging pyridine and the forced shortest non-covalent distance between two CO32- species

The aerobic reaction of the multidentate ligand 2,6-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine, H4L, with Co(ii) salts in strong basic conditions produces the clusters [Co4(L)2(OH)(py)7]NO3 (1) and [Co8Na4(L)4(OH)2(CO3)2(py)10](BF4)2 (2). Analysis of their structure unveils unusual coordination features including a very rare bridging pyridine ligand or two trapped carbonate anions within one coordination cage, forced to stay at an extremely close distance (dO···O = 1.946 Å). This unprecedented non-bonding proximity represents a meeting point between long covalent interactions and "intermolecular" contacts. These original motifs have been analysed here through DFT calculations, which have yielded interaction energies and the reduced repulsion energy experimented by both CO32- anions when located in close proximity inside the coordination cage.

Self-assembly of two high-nuclearity manganese calixarene-phosphonate clusters: diamond-like Mn16 and drum-like Mn14

Variation of the phosphonic acid “converts” a tetradecanuclear drum-like MnII14 cluster (1) into a hexadecanuclear diamond-like MnII16 cluster (2).

Constructing calixarene-supported high nuclearity Co27, Co28 and Ni18Na6 clusters with triazoles as co-bridges

Four high nuclearity compounds are constructed by M₄-calixarene SBUs and triazole co-bridges.