Antitumor effects of a Sb-rich polyoxometalate on non-small-cell lung cancer by inducing ferroptosis and apoptosis.

Polyoxometalates (POMs) are a class of anionic metal-oxygen clusters with versatile biological activities. Over the past decade, an increasing number of POMs, especially Sb-rich POMs, have been proven to exert antitumor activity. However, the antitumor effects and mechanisms of POMs in the treatment of non-small cell lung cancer (NSCLC) remain largely unexplored. This study employed a Sb-rich {Sb21Tb7W56} POM (POM-1) for NSCLC therapy and investigated its mechanism of action. Our results demonstrated that POM-1 exhibited cytotoxicity against H1299 and A549 cells with IC50 values of 3.245 µM and 3.591 µM, respectively. The migration and invasion were also inhibited by 28.05% and 76.18% in H1299 cells, as well as 36.88% and 36.98% in A549 cells at a concentration of 5 µM. In a tumor xenograft mouse model, POM-1 suppressed tumor growth by 76.92% and 84.62% at doses of 25 and 50 mg kg-1, respectively. Transcriptomic analysis indicated the alteration of ferroptosis and apoptosis signaling pathways in POM-treated NSCLC cells. Subsequent experimentation confirmed the induction of ferroptosis, evidenced by 5.6-fold elevated lipid peroxide levels with treatment of 5 µM POM-1, alongside increased expression of ferroptosis-associated proteins. Additionally, the apoptosis induced by POM-1 was also validated by the 19.67% and 30.1% increase in apoptotic cells in H1299 and A549 cells treated with 5 µM POM-1, respectively, as well as the upregulated activation of caspase-3. In summary, this study reveals, for the first time, ferroptosis as the antitumor mechanism of Sb-rich POM, and that synergism with ferroptosis and apoptosis is a highly potent antitumor strategy for POM-based antitumor therapy.

Indium-Assisted Construction of {SiNb18O54}-Based Aggregates and Their Assembly into Extended Polyoxoniobate Architectures.

In this research, indium ions were introduced into polyoxoniobates (PONbs) reaction systems to facilitate the construction of different {SiNb18O54}-based aggregates, including an {In(en)2{SiNb18O54}2} (en = ethylenediamine) dimer, an {[InO2][In2(en)O3]2{SiNb18O54}3} trimer, and an {[In(en)2][InO2][In7(en)5O9]{SiNb18O54}4} tetramer. Interestingly, these aggregates were further assembled into three uncommon extended PONb architectures in the presence of [Cu(en)2]2+ complexes, namely, H3[Cu(en)2(H2O)][Cu(en)2]6[Cu(en)2]2{[In(en)2][K2{SiNb18O54}(H2O)6]2}·1.5en·16H2O, H9{[Cu(en)2]6{[Cu(en)2]3[Cu(en)2(H2O)][In(H2O)2][In2(en)(H2O)2(OH)]2{SiNb18O54}3}·5en·29H2O, and H14[Cu(en)2]0.5[Cu(en)2(H2O)]{[Cu(en)2]2{[Cu(en)2]3[Cu(en)2(H2O)]5[K(H2O)2][In(H2O)2][In(en)2][In7(OH)9(en)5]{SiNb18O54}4}·7en·39H2O. In addition, all of them have good water vapor adsorption capacities and moderate proton transport capabilities. The above results indicate that introducing suitable heteroatoms to induce the aggregation PONb building blocks and further assembling them into new structures is an effective strategy to enrich the PONbs' structural diversity and develop new functional materials.

Development of non-closed silver clusters by transition-metal-coordination-cluster substituted polyoxometalate templates.

Nature seems to favor the formation of closed anion-templated silver clusters. How precisely to create non-closed sliver clusters remains an interesting challenge. In this work, we propose that the use of transition-metal-coordination-cluster substituted polyoxometalates (TMCC-substituted POMs) as templates is an effective synthetic strategy for creating the non-closed silver clusters, as demonstrated by the obtainment of four types of rare non-closed silver cluster species of Ag38-TM (TM = Co, Ni or Zn), Ag37-Zn, {Ag37-Zn}∞ and Ag36-TM (TM = Co, Ni). The idea of the strategy is to employ the TMCC-substituted POMs containing cluster modules with different bond interactions with Ag+ ions as templates to guide the formation of the non-closed silver clusters. For example, TMCC-substituted POM clusters are used as templates in this work, which contain POM modules that can coordinate with the Ag+ ions and TMCC moieties that are difficult to coordinate with the Ag+ ions, leading to the Ag+ ions being unable to form closed clusters around TMCC-substituted POM templates. The work demonstrates a promising approach to developing intriguing and unexplored non-closed silver clusters.

An Unusual Crystalline Porous Framework Constructed from Multitypes of Cages with Proton Conduction Property and Heterogeneous Catalytic Activity for Pyrazole Synthesis.

An unusual crystalline porous framework constructed from four types of cages, including all-inorganic Keggin-type polyoxometalate (POM) cages [H3W12O40]5-, organic hexamethylenetetramine (Hmt) cages, nanosized silver-Hmt coordination cages, and giant POM-silver-Hmt cages, was hydrothermally synthesized and structurally characterized. The framework features a highly symmetrical structure with one-dimensional nanoscale channels and holds good thermal/solvent stability, which endow it with proton conduction properties and heterogeneous catalytic activity for pyrazole. This paper not only contributes to broadening the structural diversity of cage-based crystalline porous framework materials but also sheds new light on the design of new functional framework materials.

A Palladium-Containing Polyoxotungstate with Anisotropic Proton Conductivity.

Here, a case of bilayer heterojunction Pd-containing polyoxotungstate (POW), connecting a Te3Pd3 ring and an Anderson-like TeW6 cluster, has been synthesized. The Anderson-like cluster is the first example in POW. The coordination of Pd in the ring with the S atom on the sulfo group breaks the traditional coordination configuration of Pd and O in polyoxometalates (POMs), enriching the structural types of Pd-containing POMs. In addition, the hybrid bilayer heterojunction structure at the molecular level not only provides high thermal stability but also results in spatial arrangement anisotropy, leading to up to five times the anisotropic proton conductivity.

Development of Stable Water-Soluble Supratomic Silver Clusters Utilizing A Polyoxoniobate-Protected Strategy: Giant Core-Shell-Type Ag8@Nb162 Fluorescent Nanocluster.

Atomically precise low-nuclearity (n<10) silver nanoclusters (AgNCs) have garnered significant interest due to their size-dependent optical properties and diverse applications. However, their synthesis has remained challenging, primarily due to their inherent instability. The present study introduces a new feasible approach for clustering silver ions utilizing highly negative and redox-inert polyoxoniobates (PONbs) as all-inorganic ligands. This strategy not only enables the creation of novel Ag-PONb composite nanoclusters but also facilitates the synthesis of stable low-nuclearity AgNCs. Using this method, we have successfully synthesized a small octanuclear rhombic [Ag8]6+ AgNC stabilized by six highly negative [LiNb27O75]14- polyoxoanions. This marks the first PONb-protected superatomic AgNC, designated as {Ag8@(LiNb27O75)6} (Ag8@Nb162), with an aesthetically spherical core-shell structure. The crystalline Ag8@Nb162 is stable under ambient conditions, What's more, it is water-soluble and able to maintain its molecular cluster structure intact in water. Further, the stable small [Ag8]6+ AgNC has interesting temperature- and pH-dependent reversible fluorescence response, based on which a multiple optical encryption mode for anti-counterfeit technology was demonstrated. This work offers a promising avenue for the synthesis of fascinating and stable PONb-protected AgNCs and sheds light on the development of new-type optical functional materials.

An Organodiphosphate-Containing Polyoxoniobate Ring and Its Assembly into a Three-Dimensional Framework through Hydrogen Bonding.

In this work, a novel organodiphosphate-containing inorganic-organic hybrid polyoxoniobate (PONb) ring {(PO3CH2CH2PO3H)4Nb8O16}4- (Nb8P8) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb8O36} motif and four {PO3CH2CH2PO3H} ligands. Interestingly, Nb8P8 can be joined together via K-H2O clusters {K2(H2O)4(OH)2} to form one-dimensional chains {[K2(H2O)4(OH)2]Nb8P8}n and further linked by {Cu(en)2}2+ (en = ethylenediamine) complexes, resulting in a three-dimensional supramolecular framework {[Cu(en)2]2[K2(H2O)4(OH)2]Nb8P8}·3en·H2O (1). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm3 g-1 (22.71 mol·mol-1) at 298 K, outperforming most of the known polyoxometalate-based materials. Impedance measurements prove that 1 can transfer protons with moderate conductivity. This study not only contributes to the structural diversity of organodiphosphate-containing PONbs and PONb rings but also provides a reference for the development of PONb-based materials with unique performance.

A tetrahedron-shaped polyoxoantimotungstate encapsulating a hexanuclear octahedral lanthanide-oxo cluster for an amperometric bromate sensor.

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(µ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 µA mM-1 and a detection limit that has reached 1.9 µM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors.

Two Unprecedented Germanoniobate Frameworks Based on High-Nuclearity Peanut-Shaped {Ge12Nb38} Clusters.

By variation of the amount of GeO2, two organic-inorganic hybrid germanoniobate frameworks with 6-connected pcu and 10-connected bct topologies were constructed from peanut-shaped {α-Ge12Nb38} and {ß-Ge12Nb38} clusters, respectively. The {α-Ge12Nb38} and {ß-Ge12Nb38} clusters contain the most Ge centers of germanoniobates reported so far. The compounds exhibit proton conduction properties with a conductivity of 3.04 × 10-4 S·cm-3 for 1 and 1.62 × 10-4 S·cm-3 for 2 at 85 °C and 98% RH. The water vapor adsorption capacities for 1 and 2 are 5.86 and 4.40 mmol·g-1, respectively.

A Metal-Free Helical Covalent Inorganic Polymer: Preparation, Crystal Structure and Optical Properties.

Helical morphologies are widely observed in nature, however, it is very challenging to prepare artificial helical polymers. Especially, precisely understanding the structure information of artificial metal-free helical covalent inorganic polymers via single-crystal X-ray diffraction (SCXRD) analysis is rarely explored. Here, we successfully prepare a novel metal-free helical covalent inorganic polymer ({[Te(C6 H5 )2 ] [PO3 (OH)]}n , named CityU-10) by introducing angular anions (HOPO3 2- ) into traditional tellurium-oxygen chains. The dynamic reversibility of the reaction is realized through the introduction of organic tellurium precursor and the slow hydrolysis of polyphosphoric acid. High-quality and large-size single crystals of CityU-10 have been successfully characterized via SCXRD, where the same-handed helical inorganic polymer chains form a pseudo-two-dimensional layer via multiple hydrogen-bonding interactions. The left-handed layers and right-handed layers alternatively stack together through weak hydrogen bonds to form a three-dimensional supramolecular structure. The single crystals of CityU-10 are found to display promising optical properties with a large birefringence. Our results would offer new guidelines for designing and preparing new crystalline covalent polymers through tellurium-based chemistry.