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.

Synthesis and Properties of Cobalt/Nickel-Iron-Antimony(III, V)-Oxo Tartrate Cluster-Based Compounds.

Two types of isostructural iron-cobalt/nickel-antimony-oxo tartrate cluster-based compounds, namely (H3O)(Me2NH2)[M(H2O)6]2[FeII2SbIII12(µ4-O)3(µ3-O)8(tta)6]·6H2O (M = Co (1); Ni (3)), H5/3[Co2.5FeII4/3FeIII3(H2O)13SbV1/3FeIII2/3(µ4-O)2(µ3-O)4SbIII6(µ3-O)2(tta)6]·2H2O (2) and H2[Ni2.25FeII1.5FeIII3(H2O)14SbV0.25FeIII0.75(µ4-O)2(µ3-O)4SbIII6(µ3-O)2(tta)6]·2H2O (4) (H4tta = tartaric acid) were synthesized via simple solvothermal reactions. All the clusters in the structures adopt sandwich configurations, that is, bilayer sandwich configuration in 1 and 3 and monolayer sandwich configuration in 2 and 4. Interestingly, the monolayer sandwiched compounds 2 and 4 represent rare examples of cluster-based compounds containing mixed-valence Sb(III, V), whose center of the intermediate layer is the co-occupied [FexSbV1-x]. This is different from that of previously reported sandwich-type antimony-oxo clusters in which the center position is either occupied by a transition metal ion or a Sb(V) alone. Thus, the discovery of title compounds 2 and 4 makes the evolution of center metal ion more complete, that is, from M, MxSbV1-x to SbV. All the title compounds were fully characterized, and the photocatalysis, proton conduction and magnetism of compounds 2 and 4 were studied.

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.

Borosilicate-Based Framework: Synthesis, Single-Crystal Structure Study, and Physical Properties.

Herein, we report the synthesis, crystal structure, and optical properties of a metal-free three-dimensional (3D) inorganic covalent framework ((H2en)[Si(B4O9)], named CityU-11, where H2en is the abbreviation for ethanediamine). With the assistance of a tiny amount of F- ions and the selection of SiO2 as Si sources, single crystals of CityU-11 can be successfully prepared under solvothermal conditions. The precise structure information on CityU-11 has been disclosed through both single-crystal X-ray diffraction (SCXRD) and low-dose high-resolution transmission electron microscopy (LD-HRTEM). The SCXRD results showed that CityU-11 crystallized in the noncentrosymmetric space group of Pnn2, while LD-HRTEM suggested that CityU-11 possessed almost the same interplanar distances of 0.6 nm for both (200) and (020) crystal planes, which finely matched with the double peaks of 2θ = 15° in the pattern of its powder X-ray diffraction (PXRD). CityU-11 also displayed an interesting optical property with a moderate birefringence of 0.0258@550 nm.

Mixed-valence compounds based on heterometallic-oxo-clusters containing Sb(III,V): crystal structures and proton conduction.

Two isostructural Co(Cd)-antimony-oxo tartrate cluster-based compounds with a one-dimensional (1-D) belt-like structure, namely H9.2[Co(H2O)6]{M0.5(H2O)3.5{M'(H2O)4[SbVO6[Co4.2(H2O)5SbIII6(µ3-O)2(tta)6]]}}2·nH2O (M = Co, M' = Co, n = 9 (1); M = Cd0.39/Co0.61, M' = Cd0.24/Co0.76, n = 7 (2); H4tta = tartaric acid), have been synthesized by solvothermal methods. It is noteworthy that the relatively rare mixed-valence Sb(III,V) exists in the structures. The anionic clusters in both compounds appear to be in a sandwich configuration; the top and bottom layers are based on {Sb3(µ3-O)(tta)3} brackets, and the intermediate layer is occupied by {SbVO6[Co4.2(H2O)5]}. The title compounds have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, thermogravimetric analyses, and UV-Vis spectroscopy. We chose compound 2 as a representative to test its proton conductivity, and the results show that the conductivity can reach 1.42 × 10-3 S cm-1 at 85 °C under 98% relative humidity.

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.

Identification of cholesterol metabolism-related subtypes in nonfunctioning pituitary neuroendocrine tumors and analysis of immune infiltration.

OBJECTIVE: This study aimed to investigate the role of cholesterol metabolism-related genes in nonfunctioning pituitary neuroendocrine tumors (NF-PitNETs) invading the cavernous sinus and analyze the differences in immune cell infiltration between invasive and noninvasive NF-PitNETs. METHODS: First, a retrospective analysis of single-center clinical data was performed. Second, the immune cell infiltration between invasive and noninvasive NF-PitNETs in the GSE169498 dataset was further analyzed, and statistically different cholesterol metabolism-related gene expression matrices were obtained from the dataset. The hub cholesterol metabolism-related genes in NF-PitNETs were screened by constructing machine learning models. In accordance with the hub gene, 73 cases of NF-PitNETs were clustered into two subtypes, and the functional differences and immune cell infiltration between the two subtypes were further analyzed. RESULTS: The clinical data of 146 NF-PitNETs were evaluated, and the results showed that the cholesterol (P = 0.034) between invasive and noninvasive NF-PitNETs significantly differed. After binary logistic analysis, cholesterol was found to be an independent risk factor for cavernous sinus invasion (CSI) in NF-PitNETs. Bioinformatics analysis found three immune cells between invasive and noninvasive NF-PitNETs were statistically significant in the GSE169498 dataset, and 34 cholesterol metabolism-related genes with differences between the two groups were obtained 12 hub genes were selected by crossing the two machine learning algorithm results. Subsequently, cholesterol metabolism-related subgroups, A and B, were obtained by unsupervised hierarchical clustering analysis. The results showed that 12 immune cells infiltrated differentially between the two subgroups. The chi-square test revealed that the two subgroups had statistically significance in the invasive and noninvasive samples (P = 0.001). KEGG enrichment analysis showed that the differentially expressed genes were mainly enriched in the neural ligand-receptor pathway. GSVA analysis showed that the mTORC signaling pathway was upregulated and played an important role in the two-cluster comparison. CONCLUSION: By clinical data and bioinformatics analysis, cholesterol metabolism-related genes may promote the infiltration abundance of immune cells in NF-PitNETs and the invasion of cavernous sinuses by NF-PitNETs through the mTOR signaling pathway. This study provides a new perspective to explore the pathogenesis of cavernous sinus invasion by NF-PitNETs and determine potential therapeutic targets for this disease.

Development of a New Heteropolyoxotantalate Cluster for Multidimensional Polyoxotantalate Materials.

A unique heteropolyoxotantalate (hetero-POTa) cluster [P2O7Ta5O14]7- (P2Ta5) was first developed using pyrophosphate as a key to open the ultrastable skeleton of the classical Lindqvist-type [Ta6O19]8- precursor. The P2Ta5 cluster can serve as a general and flexible secondary building unit to create a family of brand-new multidimensional POTa architectures. This work not only promotes the limited structural diversity of hetero-POTa but also provides a practical strategy for new extended POTa architectures.

Photochromic Polyoxoniobates with Photoinduced "D-f-A" Electron Transfer Mechanism.

Compounds with redox activities have appealing applications in catalytic, electronic and magnetic properties, but the redox inert of polyoxoniobates (PONbs) significantly limits their applications for a long time. In this work, we are able to integrate organophosphate and lanthanide cluster into PONb to create the first family of inorganic-organic hybrid organophosphate-Ln-PONb composite clusters. These novel species not only present the first family of redox active PONbs that can be reduced to form long-lived "heteropoly blues" under ambient conditions, but also a new photochromic system. More importantly, the analyses of the electronic configurations and photochromic properties for a series of designed proof-of-concept PONbs models allow us to discover a D-f-A electron transfer mechanism, that is, photoinduced electron is transferred from a photosensitive organophosphate electron donor (D) to the NbV electron acceptor (A) through the unoccupied 4 f-orbitals of Ln (f). This work paves the way for developing diverse PONb-based redox materials and expanding the possibility of the applications of PONbs in the redox chemistry.

Core-Shell-Type All-Inorganic Heterometallic Nanoclusters: Record High-Nuclearity Cobalt Polyoxoniobates for Visible-Light-Driven Photocatalytic CO2 Reduction.

Only rarely have polyoxometalates been found to form core-shell nanoclusters. Here, we succeeded in isolating a series of rare giant and all-inorganic core-shell cobalt polyoxoniobates (Co-PONbs) with diverse shapes, nuclearities and original topologies, including 50-nuclearity {Co12 Nb38 O132 }, 54-nuclearity {Co20 Nb34 O128 }, 62-nuclearity {Co26 Nb36 O140 } and 87-nuclearity {Co33 Nb54 O188 }. They are the largest Co-PONbs and also the polyoxometalates containing the greatest number of Co ions and the largest cobalt clusters known thus far. These molecular Co-PONbs have intriguing and atomically precise core-shell architectures comprising unique cobalt oxide cores and niobate oxide shells. In particular, the encapsulated cobalt oxide cores with different nuclearities have identical compositions, structures and mixed-valence Co3+ /Co2+ states as the different sized Co-O moieties of the bulk cubic-spinel Co3 O4 , suggesting that they can serve as various molecular models of the cubic-spinel Co3 O4 . The successful construction of the series of the Co-PONbs reveals a feasible and versatile synthetic method for making rare core-shell heterometallic PONbs. Further, these new-type core-shell bimetal species are promising cluster molecular catalysts for visible-light-driven CO2 reduction.

Oxalate-assisted assembly of two polyoxotantalate supramolecular frameworks with proton conduction properties.

An oxalate-assisted strategy was first developed for creating new polyoxotantalates (POTas). With this strategy, two brand-new POTa supramolecular frameworks based on uncommon dimeric POTa secondary building units (SBUs) were constructed and characterized. Interestingly, the oxalate ligand can not only serve as a coordination ligand to form unique POTa SBUs but also act as a key hydrogen bond acceptor to construct supramolecular architectures. Besides, the architectures show outstanding proton conductivity. The strategy opens up new opportunities for developing new POTa materials.

The first polyoxoniobate-templated silver cluster with temperature-dependent luminescent emission.

The compound [(Nb6O19)@Ag34(tBuCC)24(CH3COO)2] (Ag34) was synthesized using the solvothermal method combined with volatilization. This was the first case, to the best of our knowledge, of isolating a silver cluster containing a polyoxoniobate (PONb) template. The luminescence, solution behavior and solid-state stability of Ag34 were studied in detail. Electrospray ionization mass spectrometry indicated that Ag34 can maintain the integrity of its skeleton in solution. Detection of temperature could be a potential application of its unique luminescent behavior. We expect this work to inspire further fabrications of PONb-templated high-nuclearity silver clusters.

Cadmium-containing windmill-like heteropolyoxoniobate macrocycle with high yield for catalyzing Knoevenagel condensation.

A rare cadmium-containing windmill-like heteropolyoxoniobate macrocycle has been successfully synthesized with stable 1-D cyclic cluster aggregates. The compound exhibited promising basic catalytic ability for Knoevenagel condensation with a high yield under mild reaction conditions and high cycling stability. The theoretical calculation showed that the promising basic catalytic ability is due to the dense and stronger basic sites of the surface terminal O atoms.

Giant Polyoxoniobate-Based Inorganic Molecular Tweezers: Metal Recognitions, Ion-Exchange Interactions and Mechanism Studies.

This work reports the interesting and unique cation-exchange behaviors of the first indium-bridged purely inorganic 3D framework based on high-nuclearity polyoxoniobates as building units. Each nanoscale polyoxoniobate features a fascinating near-icosahedral core-shell structure with six pairs of unique inorganic "molecular tweezers" that have changeable openings for binding different metal cations via ion-exchanges and exhibit unusual selective metal-uptake behaviors. Further, the material has high chemical stability so that can undergo single-crystal-to-single-crystal metal-exchange processes to produce a dozen new crystals with high crystallinity. Based on these crystals and time-dependent metal-exchange experiments, we can visually reveal the detailed metal-exchange interactions and mechanisms of the material at the atomic precision level. This work demonstrates a rare systematic and atomic-level study on the ion-exchange properties of nanoclusters, which is of significance for the exploration of cluster-based ion-exchange materials that are still to be developed.

Proton-Conductive Polyoxometalate Architectures Constructed from Lanthanide-Incorporated Polyoxoniobate Cages.

Two new extended polyoxometalate (POM) architectures based on lanthanide-incorporated polyoxoniobate (Ln-incorporated PONb) cages, namely, H4[CuII(en)2]4{K4(H2O)2[CuII(en)2]5[CuII5(trz)2(en)4(OH)2][Dy2CuII2(en)2(CO3)3(H2O)2(OH)3][Dy(H2O)4][DyNb23O68(H2O)4]2}·60H2O (1, en = ethylenediamine) and H20[CuII(en)2]4{[CuII(en)2]4[Dy2(C2O4)(H2O)4]2[(Nb32(OH)4(H2O)3O89]2}·54H2O (2), have been successfully synthesized and structurally characterized, demonstrating a feasible strategy to develop functional POM materials. In addition, the proton conductivity and magnetic behaviors of both 1 and 2 were studied.

Assemblies of Increasingly Large Ln-Containing Polyoxoniobates and Intermolecular Aggregation-Disaggregation Interconversions.

An oxalate-assisted lanthanide (Ln) incorporation strategy is first demonstrated for creating rare high-nuclearity Ln-containing polyoxoniobates (PONbs). With the strategy, a series of high-nuclearity Ln-containing PONbs of 50-nuclearity Dy2Nb48, 103-nuclearity Dy7Nb96, 200-nuclearity Dy10Nb190, and 206-nuclearity Dy14Nb192 have been made, showing an increasingly large structure evolution from Dy2Nb48 monomer to Dy7Nb96 dimer and to distinct Dy10Nb190 and Dy14Nb192 tetramers. Among them, Dy14Nb192 presents the largest heterometallic PONb and also the PONb with the greatest number of Ln ions reported thus far. Interestingly, both giant Dy14Nb192 and Dy10Nb190 molecules can further undergo single-crystal to single-crystal intermolecular aggregations, forming infinite {Dy14Nb192}∞ and {Dy10Nb190}∞ chains, respectively. The former structural transformation shows a reversible humidity-dependent aggregation-disaggregation process accompanied by a proton conductivity response, while the latter structural transformation is irreversible. These new species largely enrich the very limited members of Ln-containing PONb family and offer rare examples for studying structural transformations between giant molecular aggregates and infinitely extended structures at the atomic level.

A Water-Soluble Antimony-Rich Polyoxometalate with Broad-Spectrum Antitumor Activities.

Herein, a giant Sb-rich polyoxometalate (POM) {Sb21 Tb7 W56 } is reported, which contains the largest number of Sb atoms in a POM so far. The Sb-rich POM has many interesting structural features and is a rare example of a soluble and water-stable giant POM. Biomedical studies indicate that the Sb-rich POM exhibits broad-spectrum antitumor activity against various cancer cell lines by reactivating the P53-dependent apoptotic processes and disrupting the mitochondrial membrane. In addition, this Sb-rich POM was capable of suppressing the growth and metastasis of a breast cancer in vivo. This work demonstrates that Sb-rich POMs are promising candidates for the development of new anticancer drugs.

A Stable 3d-4f Heterometallic Cluster with Magneto-Optical Activity.

A stable 3d-4f heterometallic cluster, namely, {Dy4Ni5L10(NO3)4(CO3)4(CH3OH)2}·CH3CN (Dy4Ni5, HL = 8-hydroxyquinoline), has been solvothermally synthesized and structurally characterized. The compound exhibits an interesting structure in which a tetrahedron based on 4f ions interpenetrates with a square pyramid based on 3d ions. Besides, a unique intermolecular interaction was found in Dy4Ni5, giving rise to its high stability not only when it is in the solid state but also when it dissolves in organic solvents. In addition, the magnetic behavior of solid Dy4Ni5 and the magneto-optical activity of the Dy4Ni5 solution were also studied.