Steerable Structural Evolvement and Adsorption Behavior of Metastable Polyoxovanadate-Based Metal-Organic Polyhedra

Promoting the advancement of the structure and function of metastable substances is challenging but worthwhile. In particular, how to harness the entangled state and evolution path of labile porous structures has been at the forefront of research in molecular self-assembly. In this work, the metastable structures of polyoxovanadate-based metal-organic polyhedra (VMOPs) can be manually regulated, including separation of the interlocked aggregate by a ligand-widening approach as well as transformation from a tetrahedral to capsule-like scaffold via a vertice-remodeling strategy. In these processes, intra- and intermolecular π···π and C-H···π interactions have been recognized as the primary driving forces. Besides being responsible for commanding the structural evolvement of VMOPs, such weak interactions were able to program their spatial arrangements and hence the adsorption performances for dye and iodine. The successful use of such a weak force-dominated design concept beacons a feasible route for customization of the function-oriented metastable structures. Separation and transformation of the interlocked metastable VMOPs have been achieved via the respective ligand-widening approach and vertice-remodeling strategy. Not only their structures but also adsorption features could be well regulated by such a weak force-dominated design concept.

The Hybridization of Polymers with Metal Oxide Clusters for the Design of Non-Fluorinated Proton Exchange Membranes

As the key component of various energy storage and conversion devices, proton exchange membranes (PEMs) have been attracting significant interest. However, their further development is limited by the high cost of perfluorosulfonic acid polymers and the poor stability of acid-dopped non-fluorinated polymers. Recently, a new group of PEMs has been developed by hybridizing polyoxometalates (POMs), a group of super acidic sub-nanoscale metal oxide clusters, with polymers. POMs can serve simultaneously as both proton sponges and stabilizing agents, and their complexation with polymers can further improve polymers' mechanical performance and processability. Enormous efforts have been focused on studying supramolecular complexation or covalent grafting of POMs with various polymers to optimize PEMs in terms of cost, mechanical properties and stabilities. This concept summarizes recent advances in this emerging field and outlines the design strategies and application perspectives employed for using POM-polymer hybrid materials as PEMs.

Phosphomolybdates for Dual-Mode Photoelectrochemical Sensing toward Trace Chromium(VI) and Tetracycline

Highly sensitive photoelectrochemical (PEC) sensors for trace carcinogens, such as heavy metal chromium(VI) [Cr(VI)] and antibiotic tetracycline (TC) are crucial. Herein, by integration of photoactive and redox phosphomolybdates with conjugated organic components, types of dual-mode PEC sensors were synthesized for sensing trace Cr(VI) and TC pollutants, with formulas of (H2bimb)2[Co2(bimb)1.5][Co(H2O)4][Co(P4Mo6O31H6)2]·6H2O (1), (H2bib)2[Co(H2O)3][Co2(H2O)5][Co(P4Mo6O31H6)2]·9H2O (2), and (H2bib)6[Co(Hbib)2(H2O)5][Co(P4Mo6O31H7)2]2·15H2O (3), where bimb represents 1,4-bis(1-imidazolyl)benzene and bib is 4,4'-bis(imidazolyl)bibphenyl. Hybrid 1 consisted of a three-dimensional framework structure constructed by Co{P4Mo6}2 clusters and one-dimensional (1D) {Co-bimb} chains, hybrid 2 exhibited 1D Co ion-bridged Co{P4Mo6}2 chains hydrogen-bonding with [H2bib]2+ cations, and hybrid 3 showed a discrete hybrid structure built upon a Co{P4Mo6}2 cluster modified by the {Co-bib} unit. Hybrids 1-3 displayed wide spectral absorption and excellent electrochemical redox properties, enabling dual-mode PEC responses to Cr(VI) reduction and TC oxidation. For Cr(VI) detection, hybrids 1-3 exhibited high sensitivities of 364.40, 225.72, and 124.29 μA·μM-1 as well as "nM" level detection limits (LODs) of 4.9, 10.0, and 11.0 nM, respectively. For TC detection, the sensitivities of hybrids 1-3 were 494.72, 308.78, and 174.03 μA·μM-1 and the LODs were 5.2, 6.1, and 12.9 nM, respectively. This research offers significant insights into designing efficient PEC sensors for the detection of environmental pollutants.

Unprecedented Organogermanium Functionalized GeIV-SbIII-Templating Polyoxotungstate Nanocluster for Photothermal-Chemodynamic Cancer Therapy

The function-oriented synthesis of polyoxometalate (POM) nanoclusters has become an increasingly important area of research. Herein, the well-known broad-spectrum anticancer drug Ge-132 which contains GeIV as potential heteroatoms and carboxyl coordination sites, is introduced to the POM system, leading to the first organogermanium functionalized GeIV-SbIII-templating POM nanocluster Na4[H2N(CH3)2]16 H18[Sm4(H2O)12W4O14Ge(CH2CH2COOH)]2[SbW9O33]4[Ge(CH2CH2COOH) SbW15O54]2·62H2O (1). An unprecedented organogermanium templating Dawson-like [Ge(CH2CH2COOH)SbW15O54]12- building block is discovered. To take advantage of the potential pharmaceutical activity of such an organogermanium-functionalized POM cluster, 1 is further composited with gold nanoparticles (NPs) to prepare 1-Au NPs, which doubles the blood circulation time of 1-based nanodrug. Efficient separation of photogenerated charges in 1-Au NPs largely boosts the photothermal conversion efficiency (PCE = 55.0%), which is nearly 2.1 times that of either single 1 (PCE = 26.7%) or Au NPs (PCE = 26.2%), and simultaneously facilitate the generation of toxic activate reactive oxygen species in tumor microenvironment. Based on these findings, it is demonstrated that 1-Au NPs are a multifunctional and renal clearable nanomedicine with great potential in photoacoustic imaging guiding photothermal-chemodynamic therapy for breast cancer.

Tetra-Ln3+-Implanted Tellurotungstates Covalently Modified by dl-Malic Acid: Proton Conduction and Photochromic Properties

Three unique dl-malic acid covalently modified tetra-Ln3+-implanted tellurotungstates [H2(CH3)2]9NaH9[Ln4(H2O)14W6O13(OH)5(Mal)2(B-α-TeW9O33)4]·48H2O [Ln = La3+ (1), Ce3+ (2), Pr3+ (3); H3Mal = dl-malic acid] were fabricated by reacting Na2TeO3, Na2WO4·2H2O, Mal, and LnCl3·6H2O with dimethylamine hydrochloride in an aqueous solution. The most prominent architectural feature of these compounds is the covalent connection mode of an organic ligand and a polyoxometallate backbone, which is relatively rare in the realm of polyoxotungstates. The tetrameric polyanion can be deemed as four [TeW9O33]8- fragments fused together via an intriguing hexanuclearity [W6O13(OH)5(Mal)2Ln4(H2O)14]13+ cluster. Impedance measurements manifest that all three complexes display splendid proton conduction properties, with an exceptional conductivity for 2 up to 2.48 × 10-2 S·cm-1 under 85 °C and 95% relative humidity. Moreover, compounds 1 and 3 exhibited fast reversible photochromic properties with allochroic half-life periods t1/2 of 1.046 and 0.544 min, respectively.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

A Giant Heterometallic Polyoxometalate Nanocluster for Enhanced Brain-Targeted Glioma Therapy

Giant heterometallic polyoxometalate (POM) clusters with precise atom structures, flexibly adjustable and abundant active sites are promising for constructing functional nanodrugs. However, current POM drugs are almost vacant in orthotopic brain tumor therapy due to the inability to effectively penetrate the blood-brain barrier (BBB) and low drug activity. Here, we designed the largest (3.0 nm × 6.0 nm) transition-metal-lanthanide co-encapsulated POM cluster {[Ce10 Ag6 (DMEA)(H2 O)27 W22 O70 ][B-α-TeW9 O33 ]9 }2 88- featuring 238 metal centers via synergistic coordination between two geometry-unrestricted Ce3+ and Ag+ linkers with tungsten-oxo cluster fragments. This POM was combined with brain-targeted peptide to prepare a brain-targeted nanodrug that could efficiently traverse BBB and target glioma cells. The Ag+ active centers in the nanodrug specifically activate reactive oxygen species to regulate the apoptosis pathway of glioma cells with a low half-maximal inhibitory concentration (5.66 μM). As the first brain-targeted POM drug, it efficiently prolongs the survival of orthotopic glioma-bearing mice.

Oxo-Replaced Polyoxometalates: There Is More than Oxygen

The presence of oxo-ligands is one of the main required characteristics for polyoxometalates (POMs), although some oxygen ions in a metallic environment can be replaced by other nonmetals, while maintaining the POM structure. The replacement of oxo-ligands offers a valuable approach to tune the charge distribution and connected properties like reducibility and hydrolytic stability of POMs for the development of tailored compounds. By assessing the reported catalytic and biological applications and connecting them to POM structures, the present review provides a guideline for synthetic approaches and aims to stimulate further applications where the oxo-replaced compounds are superior to their oxo-analogues. Oxo-replacement in POMs deserves more attention as a valuable tool to form chemically activated precursors for the synthesis of novel structures or to upgrade established structures with extraordinary properties for challenging applications.

Polyoxometalate-based nanocomposites for antitumor and antibacterial applications

Polyoxometalates (POMs), as emerging inorganic metal oxides, have been shown to have significant biological activity and great medicinal value. Nowadays, biologically active POM-based organic-inorganic hybrid materials have become the next generation of antibacterial and anticancer drugs because of their customizable molecular structures related to their highly enhanced antitumor activity and reduced toxicity to healthy cells. In this review, the current developed strategies with POM-based materials for the purpose of antibacterial and anticancer activities from different action principles inducing cell death and hyperpolarization, cell plasma membrane destruction, interference with bacterial respiratory chain and inhibiting bacterial growth are overviewed. Moreover, specific interactions between POM-based materials and biomolecules are highlighted for a better understanding of their antibacterial and anticancer mechanisms. POMs have great promise as next-generation antibacterial and anticancer drugs, and this review will provide a valuable systematic reference for the further development of POM-based nanomaterials.

Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

Supramolecular assemblies of organo-functionalised hybrid polyoxometalates: from functional building blocks to hierarchical nanomaterials

This review provides a comprehensive overview of recent advances in the supramolecular organisation and hierarchical self-assembly of organo-functionalised hybrid polyoxometalates (hereafter referred to as hybrid POMs), and their emerging role as multi-functional building blocks in the construction of new nanomaterials. Polyoxometalates have long been studied as a fascinating outgrowth of traditional metal-oxide chemistry, where the unusual position they occupy between individual metal oxoanions and solid-state bulk oxides imbues them with a range of attractive properties (e.g. solubility, high structural modularity and tuneable properties/reactivity). Specifically, the capacity for POMs to be covalently coupled to an effectively limitless range of organic moieties has opened exciting new avenues in their rational design, while the combination of distinct organic and inorganic components facilitates the formation of complex molecular architectures and the emergence of new, unique functionalities. Here, we present a detailed discussion of the design opportunities afforded by hybrid POMs, where fine control over their size, topology and their covalent and non-covalent interactions with a range of other species and/or substrates makes them ideal building blocks in the assembly of a broad range of supramolecular hybrid nanomaterials. We review both direct self-assembly approaches (encompassing both solution and solid-state approaches) and the non-covalent interactions of hybrid POMs with a range of suitable substrates (including cavitands, carbon nanotubes and biological systems), while giving key consideration to the underlying driving forces in each case. Ultimately, this review aims to demonstrate the enormous potential that the rational assembly of hybrid POM clusters shows for the development of next-generation nanomaterials with applications in areas as diverse as catalysis, energy-storage and molecular biology, while providing our perspective on where the next major developments in the field may emerge.

The Intrinsic Enzyme Activities of the Classic Polyoxometalates

The mimicking enzyme activities of eighteen classic POMs with different structures, Keggin (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₄GeW₁₂O₄₀, K₄GeW₁₂O₄₀, H₃PMo₁₂O₄₀, H₄SiMo₁₂O₄₀ and Eu₃PMo₁₂O₄₀), Wells-Dawson (H₆P₂Mo₁₈O₆₂, α-(NH₄)₆P₂W₁₈O₆₂ and α-K₆P₂W₁₈O₆₂·14H₂O), lacunary-Keggin (Na₈H[α-PW₉O₃₄], Na₁₀[α-SiW₉O₃₄], Na₁₀[α-GeW₉O₃₄] and K₈[γ-SiW₁₀O₃₆]), the transition-metal substituted-type (α-1,2,3-K₆H[SiW₉V₃O₃₄] and H₅PMo₁₀V₂O₄₀), sandwich-type (K₁₀P₂W₁₈Fe₄(H₂O)₂O₆₈) and an isopolyoxotungstate (Na₁₀H₂W₁₂O₄₂) were screened and compared. The mechanisms and reaction conditions of POMs with mimicking enzyme-like activities were also analyzed. The results shown that the structures, the hybrid atoms, the coordination atoms, the substituted metal atoms, pH and substrate are the effect factors for the enzyme mimic activities of POM. Among the eighteen POMs, H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₄GeW₁₂O₄₀, α-(NH₄)₆P₂W₁₈O₆₂, α-K₆P₂W₁₈O₆₂·14H₂O, Na₈H[α-PW₉O₃₄], Na₁₀[α-SiW₉O₃₄], Na₁₀[α-GeW₉O₃₄], K₈[γ-SiW₁₀O₃₆], K₁₀P₂W₁₈Fe₄(H₂O)₂O₆₈ and Na₁₀H₂W₁₂O₄₂ had the peroxidase activities. Eu₃PMo₁₂O₄₀, H₃PMo₁₂O₄₀, H₄SiMo₁₂O₄₀, α-1,2,3-K₆H [SiW₉V₃O₃₄], H₆P₂Mo₁₈O₆₂ and H₅PMo₁₀V₂O₄₀ showed the oxidase-like activities. K₄GeW₁₂O₄₀ did not show the peroxidase and oxidase activities. The Na₈H[α-PW₉O₃₄], Na₁₀[α-SiW₉O₃₄] and Na₁₀[α-GeW₉O₃₄] showed intrinsic enzyme activities at alkaline conditions, which were different from other type of POMs. The sandwich-type K₁₀P₂W₁₈Fe₄(H₂O)₂O₆₈ displayed the strongest peroxidase activity, which is similar to natural horseradish peroxidase.

The Synthesis and Biological Function of a Novel Sandwich-Type Complex Based on {SbW9 } and Flexible bpp Ligand

A novel sandwich-type complex [Na(H₂ O)₄ ][{Na₃ (H₂ O)₅ }{Mn₃ (bpp)₃ } (SbW₉ O₃₃ )₂ }]·8H₃ O (MnSbW-bpp) (bpp = 1,3-bis(4-pyridyl) propane) is synthesized and characterized by elemental analysis, IR, thermogravimetric analysis, and single-crystal X-ray diffraction. The MnSbW-bpp compound is the first sandwich case bridged by a flexible ligand. Its biological function of MnSbW-bpp in antitumor activity is also determined in vitro and in vivo. The inhibitory proliferation and induction of apoptosis are performed by flow cytometry assay, S180 (sarcoma) tumor xenograft in ICR mice, the color Doppler ultrasound monitor, and TdT-mediated dUTP-biotin nick end labeling assay. The results show that the novel compound-MnSbW-bpp-is synthesized and identified by its physical and chemical characteristics, such as the fluorescent and paramagnetic activities. MnSbW-bpp indicates a potency inhibition of human cancer lines, such as SGC-7901, HT-29, HepG2, Hela, U2OS, SaoS2, and HMC cells. MnSbW-bpp also inhibits the growth of tumor xenograft in mice, induced cell apoptosis, and released cytochrome c in vivo and in vitro. Thus, MnSbW-bpp, as a new compound, possesses the potent inhibition of cancer cells, which indicates that the MnSbW-bpp has potential merit for the further evaluation of a novel antitumor agent.

Polyoxometalates as Potential Next-Generation Metallodrugs in the Combat Against Cancer

Polyoxometalates (POMs) are an emerging class of inorganic metal oxides, which over the last decades demonstrated promising biological activities by the virtue of their great diversity in structures and properties. They possess high potential for the inhibition of various tumor types; however, their unspecific interactions with biomolecules and toxicity impede their clinical usage. The current focus of the field of biologically active POMs lies on organically functionalized and POM-based nanocomposite structures as these hybrids show enhanced anticancer activity and significantly reduced toxicity towards normal cells in comparison to unmodified POMs. Although the antitumor activity of POMs is well documented, their mechanisms of action are still not well understood. In this Review, an overview is given of the cytotoxic effects of POMs with a special focus on POM-based hybrid and nanocomposite structures. Furthermore, we aim to provide proposed mode of actions and to identify molecular targets. POMs are expected to develop into the next generation of anticancer drugs that selectively target cancer cells while sparing healthy cells.

Modulation of the mechanism of apoptosis in cancer cell lines by treatment with silica-based nanostructured materials functionalized with different metallodrugs

The mesoporous silica-based material SBA-15 (Santa Barbara Amorphous-15) has been modified with the aminodiol ligand 3-[bis(2-hydroxyethyl)amino]propyltriethoxysilane (PADOH) to give the corresponding material SBA-PADOH. Subsequent functionalization with a diorganotin(iv) compound, SnPh2Cl2 (1), and with two titanocene derivatives, TiCp2Cl2 ([Ti(η5-C5H5)2Cl2] (2)) and TiCpCpPhNfCl2 ([Ti(η5-C5H5)(η5-C5H4CHPhNf)Cl2] (3) (Ph = C6H5; Nf = C10H7)), gave the materials SBA-PADO-SnPh2 (M1), SBA-PADO-TiCp2 (M2) and SBA-PADO-TiCpCp* (M3), respectively. SBA-PADOH and M1-M3 have been characterized by various techniques such as FT-IR, XRD, XRF, solid-state NMR, nitrogen adsorption-desorption isotherms, electrochemical methods, SEM and TEM, observing that the functionalization has mainly taken place inside the pores of the corresponding porous system. In addition, mechanistic aspects of the apoptosis triggered by the synthesized materials have been studied in vitro in tumour cell lines derived from three distinct types of cancer in order to elucidate their growth inhibition and interference with the expression of tumour necrosis factor alfa (TNF-α) and the first apoptosis signal receptor (Fas or tumour necrosis factor receptor 6). It was observed that the antiproliferative and proapoptotic capacity of the materials depends on their functionalization with the different cytotoxic prodrugs (organotin or titanocene derivatives). The study shows that M1-M3 influence the metabolic activity of the tumour cells and modulate the apoptotic pathways by different mechanisms, according to the active compound inside the material.

A Series of Weakley-type Polyoxomolybdates: Synthesis, Characterization, and Magnetic Properties by a Combined Experimental and Theoretical Approach

Using DCC as the dehydrating agent, a series of Weakley-type polyoxomolybdates [Bu₄N]₃{Ln[Mo₅O₁₃(OMe)₄(NO)]₂} (Ln = Tb, Dy, Ho, Er) were synthesized in a one-pot reaction and structurally characterized by elemental, IR, UV-vis analysis, PXRD, and single-crystal X-ray diffraction. Furthermore, the static and dynamic measurements were utilized to investigate their magnetic performances. Typically, slow relaxation of magnetization was observed for Dy analogues with an energy barrier for the reversal of the magnetization of 50 K, which is the highest barrier height observed on the polyoxomolybdates-based single-molecule magnets (SMMs). For a deep understanding of the appearance of the SMM behavior on Weakley-type polyoxomolybdates series, ab initio calculations on {Dy[Mo₅O₁₃(OMe)₄(NO)]₂}^3- have been conducted.

Selective Isolation of Myosin Subfragment-1 with a DNA-Polyoxovanadate Bioconjugate

The bioconjugation of a polyoxometalate (POMs), i.e., dodecavanadate (V₁₂O₃₂), to DNA strands produces a functional labeled DNA primer, V₁₂O₃₂-DNA. The grafting of DNA primer onto streptavidin-coated magnetic nanoparticles (SVM) produces a novel composite, V₁₂O₃₂-DNA@SVM. The high binding-affinity of V₁₂O₃₂ with the ATP binding site in myosin subfragment-1 (S1) facilitates favorable adsorption of myosin, with an efficiency of 99.4% when processing 0.1 mL myosin solution (100 μg mL^-1) using 0.1 mg composite. Myosin adsorption fits the Langmuir model, corresponding to a theoretical adsorption capacity of 613.5 mg g^-1. The retained myosin is readily recovered by 1% SDS (m/m), giving rise to a recovery of 58.7%. No conformational change is observed for myosin after eliminating SDS by ultrafiltration. For practical use, high-purity myosin S1 is obtained by separation of myosin from the rough protein extract from porcine left ventricle, followed by digestion with α-chymotryptic and further isolation of S1 subfragment. The purified myosin S1 is identified with matrix-assisted laser desorption/ionization time-of-flight/mass spectrometry, giving rise to a sequence coverage of 38%.

Anticancer Activity of Polyoxometalate-Bisphosphonate Complexes: Synthesis, Characterization, In Vitro and In Vivo Results

We synthesized a series of polyoxometalate-bisphosphonate complexes containing MoVIO6 octahedra, zoledronate, or an N-alkyl (n-C6 or n-C8) zoledronate analogue, and in two cases, Mn as a heterometal. Mo6L2 (L = Zol, ZolC6, ZolC8) and Mo4L2Mn (L = Zol, ZolC8) were characterized by using single-crystal X-ray crystallography and/or IR spectroscopy, elemental and energy dispersive X-ray analysis and 31P NMR. We found promising activity against human nonsmall cell lung cancer (NCI-H460) cells with IC50 values for growth inhibition of ∼5 μM per bisphosphonate ligand. The effects of bisphosphonate complexation on IC50 decreased with increasing bisphosphonate chain length: C0 ≈ 6.1×, C6 ≈ 3.4×, and C8 ≈ 1.1×. We then determined the activity of one of the most potent compounds in the series, Mo4Zol2Mn(III), against SK-ES-1 sarcoma cells in a mouse xenograft system finding a ∼5× decrease in tumor volume than found with the parent compound zoledronate at the same compound dosing (5 μg/mouse). Overall, the results are of interest since we show for the first time that heteropolyoxomolybdate-bisphosphonate hybrids kill tumor cells in vitro and significantly decrease tumor growth, in vivo, opening up new possibilities for targeting both Ras as well as epidermal growth factor receptor driven cancers.

[V4Mo3O14(NAr)3(μ2-NAr)3]2−: the first polyarylimido-stabilized molybdovanadate cluster

This work presents the first polyarylimido-stabilized molybdovanadate cluster, which will enrich polyoxometalate chemistry and lead to more potential POM-based materials.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

This perspective provides a comprehensive description of the different roles of POMs in their interaction with relevant biological molecules.

Hetero-metallic, functionalizable polyoxomolybdate clusters via a “top-down” synthetic method

Two bi-metallic, organophosphonate-stabilised sandwich-type polyoxomolybdate clusters, [Mo₆Cu₄O₁₆(OH)₂(C₄H₉PO₃)₄(C₅H₅N)₂(CH₃O)₄(H₂O)]²⁻and [Mo₇Cu₇O₁₉(OH)(CH₃O)₇(C₄H₉PO₃)₆(C₅H₅N)₂]²⁻, are reported.

Degradable Organically-Derivatized Polyoxometalate with Enhanced Activity against Glioblastoma Cell Line

High efficacy and low toxicity are critical for cancer treatment. Polyoxometalates (POMs) have been reported as potential candidates for cancer therapy. On accounts of the slow clearance of POMs, leading to long-term toxicity, the clinical application of POMs in cancer treatment is restricted. To address this problem, a degradable organoimido derivative of hexamolybdate is developed by modifying it with a cleavable organic group, leading to its degradation. Of note, this derivative exhibits favourable pharmacodynamics towards human malignant glioma cell (U251), the ability to penetrate across blood brain barrier and low toxicity towards rat pheochromocytoma cell (PC12). This line of research develops an effective POM-based agent for glioblastoma inhibition and will pave a new way to construct degradable anticancer agents for clinical cancer therapy.

Lanthanide-Connecting and Lone-Electron-Pair Active Trigonal-Pyramidal-AsO3 Inducing Nanosized Poly(polyoxotungstate) Aggregates and Their Anticancer Activities

By virtue of the stereochemical effect of the lone-electron pair located on the trigonal-pyramidal-AsO3 groups and the one-pot self-assembly strategy in the conventional aqueous solution, a series of novel lanthanide-bridging and lone-electron-pair active trigonal-pyramidal-AsO3 inducing nanosized poly(polyoxotungstate) aggregates [H2N(CH3)2]6 Na24H16{[Ln10W16(H2O)30O50](B-α-AsW9O33)8}·97H2O [Ln = Eu(III) (1), Sm(III) (2), Gd(III) (3), Tb(III) (4), Dy(III) (5), Ho(III) (6), Er(III) (7), Tm(III) (8)] were prepared and further characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric (TG) analyses and single-crystal X-ray diffraction. The most remarkable structural feature is that the polyanionic skeleton of {[Ln10W16(H2O)30O50](B-α-AsW9O33)8}(46-) is constructed from eight trivacant Keggin [B-α-AsW9O33](9-) fragments through ten Ln centers and sixteen bridging W atoms in the participation of fifty extraneous oxygen atoms. Notably, 4 and 8 can be stable in the aqueous solution not only for eight days but also in the range of pH = 3.9-7.5. Moreover, the cytotoxicity tests of 4 and 8 toward human cervical cancer (HeLa) cells, human breast cancer (MCF-7) cells and mouse fibroblast (L929) cells were performed by the 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and the cell apoptosis processes were characterized by calcein AM/PI staining experiments, annexin V-FITC/PI staining experiments and morphological changes.

A general and highly regioselective synthesis approach to multi-functionalized organoimido derivatives of Polyoxometalates

Organoimidoylization of Polyoxometalates (POMs) can dramatically modify the electronic structures of POMs and gives rise to novel “value-adding” properties of the POMs for promising material applications including photo-electronic transformation and catalysis. To date, the preparation of multi-functionalized organoimido derivatives of POMs is generally conducted under strict condition and is time-consuming with limited yields. Herein, a series of regioselective polyorganoimido derivatives of POMs, ocatant- [Mo₆O₁₃(NAr)₃(μ₂-NAr)₃]²⁻ (Ar = phenyl (1), p-methoxyphenyl (2) and p-ethylphenyl (3)), were synthesized with high selectivity and in good yields via a general and highly regioselective synthesis method, called as the one-octant synthesis protocol. The reaction was monitored by ESI-MS and the as-prepared products were studied by ESI-MS, IR, UV-Vis, EA, ¹HNMR, single crystal XRD analysis and DFT calculations. The one-octant synthesis protocol here may serve as an idea method to design novel nanoscale POM-based organic-inorganic multi-functional hybrids.

Biofunctionalization of Polyoxometalates with DNA Primers, Their Use in the Polymerase Chain Reaction (PCR) and Electrochemical Detection of PCR Products

The bioconjugation of polyoxometalates (POMs), which are inorganic metal oxido clusters, to DNA strands to obtain functional labeled DNA primers and their potential use in electrochemical detection have been investigated. Activated monooxoacylated polyoxotungstates [SiW11 O39 {Sn(CH2 )2 CO}](8-) and [P2 W17 O61 {Sn(CH2 )2 CO}](6-) have been used to link to a 5'-NH2 terminated 21-mer DNA forward primer through amide coupling. The functionalized primer was characterized by using a battery of techniques, including electrophoresis, mass spectrometry, as well as IR and Raman spectroscopy. The functionality of the POM-labeled primers was demonstrated through hybridization with a surface-immobilized probe. Finally, the labeled primers were successfully used in the polymerase chain reaction (PCR) and the PCR products were characterized by using electrophoresis.

Microwave assisted synthesis of a mono organoimido functionalized Anderson polyoxometalate

The synthesis of an aliphatic organoimido functionalized polyoxometalate has been achieved through a microwave assisted reaction protocol in the absence of any activating reagents.