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.

N-N-Bridged Polynuclear POM-Based Coordination Polymers Based on a V-Type Ligand: Proton Conduction and Magnetism

The construction of polyoxometalate (POM)-based coordination polymers, in the presence of a nitrogen heterocyclic ligand, is intriguing due to the potential for obtaining diverse structures. These structures exhibit extensive application possibilities in the fields of proton conductivity and magnetism. Herein, four new POM-based polynuclear coordination polymers with the formulas of {[Fe2(btb)3(H2O)2(SiW12O40)]·3H2O}n (1), {[Cd2(btb)2(H2O)6(HPMoVI10MoV2O40)]·2H2O}n (2), {[Co3(OH)2(btb)2(H2O)5(HPMoVI10MoV2O40)]·7H2O}n (3), and {[Cu3(OH)(btb)2(H2O)(HP2Mo5O23)]·6H2O}n (4) have been prepared using the V-type 1,3-bis(4H-1,2,4-triazole-4-yl)benzene (btb) ligand. Compounds 1 and 2 feature similar two-dimensional (2D) structures, derived from the binuclear Fe2N6 and Cd2N4 subunits connected by tridentate btb ligands. Meanwhile, in compound 3, hexanuclear Co6(OH)4 units are bound by quadridentate btb ligands forming a 2D layer with the same 4-c sql topology simplification as compounds 1 and 2. In compound 1, Keggin-type polyoxoanions are monodentate-coordinated to metal ions and suspended on the 2D structure, while, in compounds 2 and 3, they act as discrete counterions residing in the interstitial spaces between two adjacent layers, thereby extending the 2D structures into 3D structures through hydrogen bonding interactions. In compound 4, trinuclear Cu3(OH) subunits are further constructed into a 3D framework through cooperation with four tridentate and quadridentate btb ligands as well as Strandberg-type anions. Furthermore, the proton conduction of the four compounds has been investigated. They display high proton conductivities at 358 K and 98% RH with powdered samples, which are 1.26 × 10-3, 1.24 × 10-3, 3.24 × 10-4, and 2.57 × 10-4 S cm-1, respectively. Interestingly, by mixing with Nafion, the composite membranes of compounds 2 and 4 exhibit enhanced proton conductivities, measuring at 4.87 × 10-2 and 1.28 × 10-2 S cm-1, respectively, at 358 K and 98% RH, which suggests excellent potential for applications. In addition, compounds 1, 3, and 4 display antiferromagnetic behaviors due to similar magnetic interactions. This work can provide research insights into the assembly of 2D POM-based coordination polymers with nitrogen heterocyclic ligands and Keggin-type POMs and further promote their research progress in proton conduction.

Dynamic and transformable Cu12 cluster-based C-H···π-stacked porous supramolecular frameworks

The assembly of cluster-based π-stacked porous supramolecular frameworks presents daunting challenges, including the design of suitable cluster building units, control of the sufficient C-H···π interactions, trade-off between structural dynamics and stability as well as understanding the resulting collective properties. Herein, we report a cluster-based C-H···π interaction-stacked porous supramolecular framework, namely, Cu12a-π, consisting of Cu12 nanocluster as a 6-connected node, which is further propagated to a dynamic porous supramolecular frameworks via dense intralayer C-H···π interactions, yielding permanent porosity. In addition, Cu12a-π can be transformed into cluster-based nonporous adaptive crystals (Cu12b-NACs) via ligand-exchange following a dissociation-reassembly mechanism. Moreover, Cu12a-π can efficiently remove 97.2% of iodine from saturated iodine aqueous solutions with a high uptake capacity of 2.96 g·g-1. These prospective results positioned at cluster-based porous supramolecular framework and enlighten follow-up researchers to design and synthesize such materials with better performance.

Assembly of cobalt-p-sulfonatothiacalix[4]arene frameworks with phosphate, phosphite and phenylphosphonate ligands

Three cobalt-calixarene coordination frameworks, namely, {[Co4Cl(H4TC4AS)]4(HPO3)8}4− (CIAC-253), {[Co4Cl(H4TC4AS)]4(PO4)8}12− (CIAC-254) and {[Co4Cl(H4TC4AS)]3(Ph-PO3)6}3− (CIAC-255) were obtained by solvothermal reaction of a cobalt salt, sodium p-sulfonatothiacalix[4]arene (Na4H4TC4AS) and phosphate, phosphite and phosphonate ligands. In CIAC-253 and CIAC-254, the shuttlecock-like Co4Cl-(TC4AS) secondary building units (SBUs) are bridged by HPO3 2− or PO4 3− anions into two quadrilateral frameworks while in CIAC-255, the Co4Cl-(TC4AS) SBUs are linked into a triangular framework by phenylphosphonate anions. The supramolecular interactions between the phenyl groups of phosphonate and TC4AS play a crucial role in the formation of the triangle. Magnetic measurements revealed that all the cobalt(II) centers exhibit antiferromagnetic interactions.

A novel series of giant cobalt-calixarene macrocycles: ring-expansion and modulation of pore apertures through recrystallization

The design and synthesis of metallomacrocycles can be quite challenging because the assemblies of such molecular cycles are difficult to control and the products are usually unpredictable. In this work, a novel series of metallomacrocycles, denoted as {Co30-A}, {Co30-B} and {Co32-A} have been synthesized via self-assembly of p-tert-butylthiacalix[4]arene (H4TC4A) and 3,5-pyrazoledicarboxylic acid (H3pdc) with Co2+ ions under solvothermal conditions. Recrystallization of {Co32-A} under different conditions was found to form {Co32-B} and {Co32-C} that have a similar ring structure to that of {Co32-A} but have different molecular packing modes in the lattices, as well as a 40-membered ring {Co40}. These complexes represent the highest-nuclearity metallocalixarene coordination wheels reported to date. Crystallographic studies indicate that all these metallomacrocycles feature wheel-like structures with apertures varing from 11.4 to 20.3 Å. It is noteworthy that {Co32-A} exhibited good efficiency in removing RhB even at low initial concentration (10 ppm) and also excellent adsorption selectivity towards RhB over Na2Fl (RhB = Rhodamine B, Na2Fl = disodium fluorescein). This work not only makes a breakthrough in the synthesis of metallocalixarene macrocycles with high nuclearity and large apertures, but also provides a simple recrystallization approach to realize the ring-expansion and regulation of molecular packing modes of the metallomacrocycles.

Thiacalix[4]arene-supported molecular clusters for catalytic applications

Thiacalixarenes are intriguing ligands that have attracted sustained interest because of their changeable conformations and excellent coordination ability. Thiacalix[4]arene analogues, which can bind metal ions to form modular second building units, are capable of constructing molecular-based functional materials with defined structures and various applications via directional coordination assembly. Due to rich metal-sulfur bonds, thiacalix[4]arene-based molecular clusters also exhibit diverse properties compared to other clusters. In particular, the combination of thiacalixarenes with currently popular molecular architectures, such as high-nuclearity clusters and coordination cages, has shown special catalytic performances. In this perspective, the latest advances in catalytic applications of thiacalix[4]arene-based molecular clusters, including molecular clusters themselves as catalysts and coordination cages serving as reaction vessels encapsulating metal nano-components for catalysis, are highlighted.

Formation of Unsymmetrical Trinuclear Metallamacrocycles Based on Two Different Cone Calix[4]arene Macrocyclic Rings

A combination of tetrasulfonylcalix[4]arene (3-4H) together with a calix[4]arene dicarboxylate derivative 2-4H led, in the presence of MII(NO3)2 (M = Co, Ni, Zn), to the formation of three novel isostructural metallomacrocycles of formula [M3(DMF)2(μ3-H2O)-(2-2H)-3]. The structure of the prepared coordination compounds was studied in the solid state using single crystal/powder X-ray diffraction studies. The X-ray diffraction on single crystal revealed that the structure of the obtained supramolecular complexes is composed of a trinuclear metallic cluster [M3]+6 held between one di-deprotonated molecule of (2-2H)2− offering two carboxylate groups for binding metal cations and one tetra-deprotonated compound 34−, where four oxygen atoms, belonging to four deprotonated phenolic moieties and three oxygen atoms coming from three SO2 groups, are coordinated with the cluster core. Thus, an example of an easily reproducible molecular recognition pattern involving two different types of calix[4]arene based ligands, displaying different coordination moieties, and trinuclear metallic clusters, is reported here. In addition, it has been shown that the cone moieties of the calixarene also encapsulate solvent molecules.

A 42-metal Yb(iii) nanowheel with NIR luminescent response to anions

One Yb42 nanowheel [Yb42L14(OH)28(OAc)84] was constructed using a tridentate vanillin ligand. The external diameter of the wheel-like structure is about 3.6 nm, which allows direct visualization by TEM. It shows interesting NIR lanthanide luminescence sensing towards anions, especially to fluoride at the ppm level.

Nuclearity control in calix[4]arene-based zinc(ii) coordination complexes

Three zinc-based coordination complexes were selectively generated in the crystalline phase using a new flexible molecular “tweezers” calix[4]arene derivative ligand decorated with two appended carboxylic moieties and benzyl spacers ((3-4H)).

Large Ln42 coordination nanorings: NIR luminescence sensing of metal ions and nitro explosives

Two 42-metal lanthanide nanorings [Ln₄₂L₁₄(OH)₂₈(OAc)₈₄] (Ln = Nd (1), La (2)) were constructed, and the Nd₄₂ cluster exhibits NIR luminescent sensing of metal cations and nitro explosives.

Structure and magnetism of two chair-shaped hexanuclear dysprosium(iii) complexes exhibiting slow magnetic relaxation

Two novel hexanuclear Dy^III complexes with polyhydroxy Schiff-base ligands, [Dy₆(L¹)₄(μ₃-OH)₄(MeOH)₄]Cl₂·2MeOH·2MeCN (1) and [Dy₆(HL²)₂(μ₃-OH)₂(μ₃-OCH₃)₂(piv)₁₀(MeOH)₂] (2) (H₃L¹ = N,N′-bis(3-methoxysalicylidene)(propylene-2-ol)-1,3-diamine, H₃L² = 2,3-dihydroxypropylimino)methyl)-6-methoxyphenol, piv = pivalate), have been prepared under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction, elemental analyses, thermal analyses, and IR spectroscopy. Each of the hexanuclear complexes is constructed with Dy₃ triangular motifs as building blocks, and the six Dy^III ions are arranged in a chair-shaped conformation. Variable-temperature magnetic susceptibility measurements in the temperature range of 2–300 K indicate dominant ferromagnetic exchange interactions between the Dy^III ions in the complexes. Both complexes exhibit slow magnetic relaxation behavior.

We report two novel chair-shaped hexanuclear Dy^III complexes with different polyhydroxy Schiff-base ligands. Both complexes are constructed with Dy₃ triangular motifs as building blocks and exhibit slow magnetic relaxation behavior at low temperature.

Thiacalix[4]arene-supported tetradecanuclear cobalt nanocage cluster as precursor to synthesize CoO/Co9S8@CN composite for supercapacitor application

A new high nuclearity N,S-co-rich Co₁₄ cage cluster was used as a precursor to synthesize CoO/Co₉S₈@CN composites for applications in supercapacitors.

A novel alb metalloring organic framework with a {Ni12Gd24} cage exhibiting a significant magnetocaloric effect

With the aid of a bifunctional 6-mercaptonicotinic acid ligand, a novel {Ni₁₂Gd₂₄} cage-based (6, 12)-c alb-MROF that is assembled from a {Gd₄(OH)₄(COO)₆} trigonal-prism building unit and a {Ni₆S₁₂} hexagonal-prism molecular building block has been synthesized for the first time. It exhibits a large MCE value of 29.86 J kg^-1 K^-1 for ΔH = 8 T at 2 K.

A single-stranded {Gd18} nanowheel with a symmetric polydentate diacylhydrazone ligand

A {Gd₁₈} nanowheel was solvothermally synthesized. It features a rare single-stranded skeleton that looks like a Reuleaux triangle with vertices buckled in, represents the highest nuclearity and the largest size in any pure Ln wheels reported, and shows a large MCE.

A family of 12-azametallacrown-4 structural motif with heterometallic Mn(III) -Ln-Mn(III) -Ln (Ln=Dy, Er, Yb, Tb, Y) alternate arrangement and single-molecule magnet behavior

Mixed 3d-4f 12-azametallacrown-4 complexes, [Mn2 Ln2 (OH)2 (hppt)4 (OAc)2 (DMF)2 ]⋅2 DMF⋅H2 O [Ln=Dy (1), Er (2), Yb (3), Tb (4) and Y (5), H2 hppt=3-(2-hydroxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole)], were synthesized by reactions of H2 hppt with Mn(OAc)2 ⋅4 H2 O and Ln(NO3 )3 ⋅6 H2 O. This is the first 3d-4f azametallacrown family to incorporate Ln ions into the ring sets. These isostructural complexes exhibit alternating arrangements of two Mn and two Ln ions in the rings with each pair of metal centers bound by an NN group and μ2 -O bridging. Magnetic measurements revealed dominant antiferromagnetic interactions between metal centers, and frequency-dependent out-of-phase (${\chi {^\prime}{^\prime}_{\rm{M}} }$) signals below 4 K suggest slow relaxation of magnetization.

Experimental and theoretical investigations of four 3d–4f butterfly single-molecule magnets

Experimental and theoretical investigations of four 3d–4f defect-dicubane single-molecule magnets.

Discrete polynuclear manganese(ii) complexes with thiacalixarene ligands: synthesis, structures and photophysical properties

The solid state luminescence of [Mn₄(ThiaSO₂)₂F]X (X = K⁺ and [K(18-crown-6)]⁺, ThiaSO₂ = p-tert-butylsulphonylcalix[4]arene) compounds show a strong O₂ pressure dependence.

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.

22-Azametallacrown-8 complex with a triazole-bridged ligand: synthesis, structure and magnetic properties

Reaction of Mn(OAc)2·4H2O with the H2L ligand affords a new manganese 22-MC-8 azametallacrown [Mn8(μ3-O)2(μ3-OH)2(μ2-OH)2(L)6(OAc)2(OH2)4]·2DMF (H2L = 3-(2-oxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole). The structural analysis of the complex reveals that the azaMC ring possesses -[Mn-O-Mn-N-N-Mn-N-N-Mn-N-N]- connectivity. The magnetic behavior of the complex shows the dominant antiferromagnetic interactions between the manganese ions with S = 4 and the frequency-dependent out-of-phase signal.