Polyoxometalate-Intercalated Tremella-Like CoNi-LDH Nanocomposites for Electrocatalytic Nitrite-Ammonia Conversion.

The electrocatalytic reduction of NO2- (NO2RR) holds promise as a sustainable pathway to both promoting the development of emerging NH3 economies and allowing the closing of the NOx loop. Highly efficient electrocatalysts that could facilitate this complex six-electron transfer process are urgently desired. Herein, tremella-like CoNi-LDH intercalated by cyclic polyoxometalate (POM) anion P8W48 (P8W48/CoNi-LDH) prepared by a simple two-step hydrothermal-exfoliation assembly method is proposed as an effective electrocatalyst for NO2- to NH3 conversion. The introduction of POM with excellent redox ability tremendously increased the electrocatalytic performance of CoNi-LDH in the NO2RR process, causing P8W48/CoNi-LDH to exhibit large NH3 yield of 0.369 mmol h-1 mgcat-1 and exceptionally high Faradic efficiency of 97.0% at -1.3 V vs the Ag/AgCl reference electrode in 0.1 M phosphate buffer saline (PBS, pH = 7) containing 0.1 M NO2-. Furthermore, P8W48/CoNi-LDH demonstrated excellent durability during cyclic electrolysis. This work provides a new reference for the application of POM-based nanocomposites in the electrochemical reduction of NO2- to obtain value-added NH3.

Polyoxometalates@Metal-Organic Frameworks Derived Bimetallic Co/Mo2 C Nanoparticles Embedded in Carbon Nanotube-Interwoven Hierarchically Porous Carbon Polyhedron Composite as a High-Efficiency Electrocatalyst for Al-S Batteries.

Al-S battery (ASB) is a promising energy storage device, notable for its safety, crustal abundance, and high theoretical energy density. However, its development faces challenges due to slow reaction kinetics and poor reversibility. The creation of a multifunctional cathode material that can both adsorb polysulfides and accelerate their conversion is key to advancing ASB. Herein, a composite composed of polyoxometalate nanohybridization-derived Mo2 C and N-doped carbon nanotube-interwoven polyhedrons (Co/Mo2 C@NCNHP) is proposed for the first time as an electrochemical catalyst in the sulfur cathode. This composite improves the utilization and conductivity of sulfur within the cathode. DFT calculations and experimental results indicate that Co enables the chemisorption of polysulfides while Mo2 C catalyzes the reduction reaction of long-chain polysulfides. X-ray photoelectron spectroscopy (XPS) and in situ UV analysis reveal the different intermediates of Al polysulfide species in Co/Mo2 C@NCNHP during discharging/charging. As a cathode material for ASB, Co/Mo2 C@NCNHP@S composite can deliver a discharge-charge voltage hysteresis of 0.75 V with a specific capacity of 370 mAh g-1 after 200 cycles at 1A g-1 .

Bifunctional K3PW12O40/Graphene Oxide-Modified Separator for Inhibiting Polysulfide Diffusion and Stabilizing Lithium Anode.

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation batteries due to their high theoretical energy density. However, the practical application of Li-S batteries is still hindered by several challenges, such as the polysulfide shuttle and the growth of lithium dendrites. Herein, we introduce a bifunctional K3PW12O40/graphene oxide-modified polypropylene separator (KPW/GO/PP) as a highly effective solution for mitigating polysulfide diffusion and protecting the lithium anode in Li-S batteries. By incorporating KPW into a densely stacked nanostructured graphene oxide (GO) barrier membrane, we synergistically capture and rapidly convert lithium polysulfides (LiPSs) electrochemically, thus effectively suppressing the shuttling effect. Moreover, the KPW/GO/PP separator can stabilize the lithium metal anode during cycling, suppress dendrite formation, and ensure a smooth and dense lithium metal surface, owing to regulated Li+ flux and uniform Li nucleation. Consequently, the constructed KPW/GO/PP separator delivered a favorable initial specific capacity (1006 mAh g-1) and remarkable cycling performance at 1.0 C (626 mAh g-1 for up to 500 cycles with a decay rate of 0.075% per cycle).

Polyoxometalate-Cyclodextrin-Based Cluster-Organic Supramolecular Framework for Polysulfide Conversion and Guest-Host Recognition in Lithium-sulfur Batteries.

Developing polyoxometalate-cyclodextrin cluster-organic supramolecular framework (POM-CD-COSF) still remains challenging due to an extremely difficult task in rationally interconnecting two dissimilar building blocks. Here we report an unprecedented POM-CD-COSF crystalline structure produced through the self-assembly process of a Krebs-type POM, [Zn2 (WO2 )2 (SbW9 O33 )2 ]10- , and two ß-CD units. The as-prepared POM-CD-COSF-based battery separator can be applied as a lightweight barrier (approximately 0.3 mg cm-2 ) to mitigate the polysulfide shuttle effect in lithium-sulfur batteries. The designed Li-S batteries equipped with the POM-CD-COSF modified separator exhibit remarkable electrochemical performance, attributed to fast Li+ diffusion through the supramolecular channel of ß-CD, efficient polysulfide-capture ability by the dynamic host-guest interaction of ß-CD, and improved sulfur redox kinetics by the bidirectional catalysis of POM cluster. This research provides a broad perspective for the development of multifunctional supramolecular POM frameworks and their applications in Li-S batteries.

High-Entropy Prussian Blue Analogues and Their Oxide Family as Sulfur Hosts for Lithium-Sulfur Batteries.

The introduction of high-entropy into Prussian blue analogues (PBAs) has yet to attract attention in the field of lithium-sulfur battery materials. Herein, we systematically synthesize a library of PBAs from binary to high-entropy by a facile coprecipitation method. The coordination environment in PBAs is explored by X-ray absorption fine structure spectroscopy, which together with elemental mapping confirm the successful introduction of all metals. Importantly, electrochemical tests demonstrate that high-entropy PBA can serve as polysulfide immobilizer to inhibit shuttle effect and as catalyst to promote polysulfides conversion, thereby boosting its outstanding performance. Additionally, a variety of nanocubic metal oxides from binary to senary are fabricated by using PBAs as sacrificial precursors. We believe that a wide range of new materials obtained from our coprecipitation and pyrolysis methodology can promote further developments in research on PBA systems and sulfur hosts.

Embedding Cobalt Atom Clusters in CNT-Wired MoS2 Tube-in-Tube Nanostructures with Enhanced Sulfur Immobilization and Catalyzation for Li-S Batteries.

Lithium-sulfur batteries are one of the most promising next-generation energy storage systems. The efficient interconversion between sulfur/lithium polysulfides and lithium sulfide is a performance-determining factor for lithium-sulfur batteries. Herein, a novel strategy to synthesize a unique tube-in-tube CNT-wired sulfur-deficient MoS2 nanostructure embedding cobalt atom clusters as an efficient polysulfide regulator is successfully conducted in Li-S batteries. It is confirmed that encapsulating MWCNTs into hollow porous sulfur-deficient MoS2 nanotubes embedded with metal cobalt clusters not only can accelerate electron transport and confine the dissolution of lithium polysulfide by physical/chemical adsorption, but also can catalyze the kinetics of polysulfide redox reactions. Based on DFT calculations, in situ spectroscopic techniques, and various electrochemical studies, catalytic effects of CNT/MoS2 -Co nanocomposite in Li-S battery are deeply investigated for the first time. The CNT/MoS2 -Co composite cathode exhibits a very remarkable rate capability (641 mAh g-1 at 5.0 C) and excellent cycling stability (capacity decay rate of 0.050% per cycle at 5.0 C) even at high sulfur mass loading of 3.6 mg cm-2 . More crucially, CNT/MoS2 -Co tube-in-tube nanostructures present a superior specific capacity of 650 mAh g-1 in a Li-S pouch cell at 0.2 C (4.0 mg cm-2 ).

Novel magnetically separable of Fe3O4/Ag3PO4@WO3 nanocomposites for enhanced photocatalytic and antibacterial activity against Staphylococcus aureus (S. aureus).

BACKGROUND: Iron oxide nanocomposites have received a great attention for their application in various fields like physics, medicine, biology, and material science etc., due to their unique properties, such as magnetism, electrical properties, small size, biocompatibility and low toxicity. METHODS: Fe3O4/Ag3PO4@WO3 nanocomposites with different weight percent of Ag3PO4 were successfully prepared through fabricated Ag3PO4/Fe3O4 with WO3 via in situ fabrication method, electrospinning involved precursor solution preparation and spinning to enhance photocatalyst performance under simulated sunlight for the degradation of methylene blue (MB) and antibacterial activity against Staphylococcus aureus (S. aureus). RESULTS: The photocatalytic degradation of methylene blue (MB) under simulated light irradiation indicated that the nanocomposite with 0.25 mg of Ag3PO4 has the best activity. An additional advantage of these photocatalysts is magnetic recoverability, using external magnetic field and photocatalytic stability of the nanocomposites was evaluated for three cycles. In addition, using different scavengers, holes (h+) and superoxide radical (O 2 ·-) radicals and hydroxide radical (·OH) were identified the main oxidative species in the degradation reaction of methylene blue. CONCLUSIONS: The results reveal that Fe3O4/Ag3PO4@WO3-0.25 nanocomposites have photocatalytic and antibacterial activity against S. aureus. The photocatalyst and mechanism based on the enhancement of electron transfer processes between Ag3PO4 and WO3 nanoparticles.

Core-Shell Structure and Interaction Mechanism of γ-MnO2 Coated Sulfur for Improved Lithium-Sulfur Batteries.

Lithium-sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g-1 and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core-shell γ-MnO2 -coated sulfur nanocomposite through the redox reaction between KMnO4 and MnSO4 . The multifunctional MnO2 shell facilitates electron and Li+ transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ-MnO2 crystallographic form also provides one-dimensional (1D) tunnels for the Li+ incorporation to alleviate insoluble Li2 S2 /Li2 S deposition at high discharge rate. More importantly, the MnO2 phase transformation to Mn3 O4 occurs during the redox reaction between polysulfides and γ-MnO2 is first thoroughly investigated. The S@γ-MnO2 composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn3 O4 phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li-S cells.

Tailoring Versatile Cathodes and Induced Anodes for Zn-Se Batteries: Anisotropic Orientation of Tin-Based Materials within Bowl-In-Ball Carbon.

The advancement of Zn-Se batteries has been hindered by significant challenges, such as the sluggish kinetics of Se cathodes, limited Se loading, and uncontrollable formation of Zn dendrites. In this study, a bidirectional optimization strategy is devised for both cathode and anode to bolster the performance of Zn-Se batteries. A novel bowl-in-ball structured carbon (BIBCs) material is synthesized to serve as a nanoreactor, in which tin-based materials are grown and derived in situ to construct cathodes and anodes. Within the cathode, the multifunctional host material (SnSe@BIBCs) exhibits large adsorption capacity for selenium, and demonstrates supreme catalytic properties and spatially confined characteristics toward the selenium reduction reaction (SeRR). On the anode, Sn@BIBCs displays triple-induced properties, including the zincophilic of the internal metallic Sn, the homogenized spatial electric field from the 3D spatial structure, and the curvature effect of the bowl-shaped carbon. Collectively, these factors induce preferential nucleation of Zn, ensuring its uniform deposition. As a result, the integrated Zn-Se battery system achieves a remarkable specific capacity of up to 603 mAh g-1 and an impressive energy density of 581 W kg-1, highlighting its tremendous potential for practical applications.

Polyoxomolybdate-Based Metal-Organic Framework-Derived Cu-Embedded Molybdenum Dioxide Hybrid Nanoparticles as Highly Efficient Electrocatalysts for Al-S Batteries.

High-performance rechargeable aluminum-sulfur batteries (RASB) have great potential for various applications owing to their high theoretical capacity, abundant sulfur resources, and good safety. Nevertheless, the practical application of RASB still faces several challenges, including the polysulfide shuttle phenomenon and low sulfur utilization efficiency. Here, we first developed a synergistic copper heterogeneous metal oxide MoO2 derived from polymolybdate-based metal-organic framework as an efficient catalyst for mitigating polysulfide diffusion. This composite enhances sulfur utilization and electrical conductivity of the cathode. DFT calculations and experimental results reveal the catalyst Cu/MoO2@C not only effectively anchors aluminum polysulfides (AlPSs) to mitigate the shuttle effect, but also significantly promotes the catalytic conversion of AlPSs on the sulfur cathode side during charging and discharging. The unique nanostructure contains abundant electrocatalytic active sites of oxide nanoparticles and Cu clusters, resulting in excellent electrochemical performance. Consequently, the established RASB exhibits an initial capacity of 875 mAh g-1 at 500 mA g-1 and maintains a capacity of 967 mAh g-1 even at a high temperature of 50 °C.

Keggin-type polyoxometalate-based crown ether complex for lithium-sulfur batteries.

A novel supramolecular complex Li3Cl[(HPW12O40)(H24C12O6)3(CH3CN)2] {CR-PW12} was confirmed first to apply as a sulfur host in lithium-sulfur batteries. The {CR-PW12}@S cathode exhibits a reversible capacity of 1120 mA h g-1 at 1.0 C and excellent cycle stability.

Protonated and deprotonated vanadyl imidazole tartrates for the mimics of the vanadium coordination in the FeV-cofactor of V-nitrogenase.

Chiral imidazole-based oxidovanadium tartrates (H2im)2[Δ,Λ-VIV2O2(R,R-H2tart)(R,R-tart)(Him)2]·Him (1, H4tart = tartaric acid, Him = imidazole) and [Λ,Λ-VIV2O2(R,R-tart)(Him)6]·4H2O (2) and their corresponding enantiomers (H2im)2[Λ,Δ-VIV2O2(S,S-H2tart)(S,S-tart)(Him)2]·Him (3) and [Δ,Δ-VIV2O2(S,S-tart)(Him)6]·4H2O (4) were obtained in alkaline solutions. Interestingly, the tartrates chelate with vanadium bidentately through α-alkoxy/α-hydroxy and α-carboxy groups and imidazole coordinates monodentately through nitrogen atom. It is worth noting that complexes 1 and 3 contain both protonated α-hydroxy and deprotonated α-alkoxy groups simultaneously, which have short V-Oα-alkoxy distances [1.976(4)av Å in 1-4] and long V-Oα-hydroxy distances [2.237(3)av Å in 1 and 2.230(2)av Å in 3]. There is an interesting strong intramolecular hydrogen bond [O(11)⋯O(1) 2.731(5) Å] between the two parts in 1 and 3. The protonated V-O distances are closer to the average bond distance in reported FeV-cofactors (FeV-cos, V-Oα-alkoxy 2.156av Å) in VFe proteins, which corresponds to the feasible protonation of coordinated α-hydroxy in R-homocitrate in V-nitrogenase, showing the homocitrate in the mechanistic model for nitrogen reduction as a secondary proton donor. Furthermore, vibrational circular dichroism (VCD) and IR spectra of 1-4 pointed out the disparity between the characteristic vibrations of the C-O and C-OH groups clearly. EPR experiment and theoretical calculations support +4 oxidation states for vanadium in 1-4. Solution 13C {1H} NMR spectra and CV analyses exhibited the solution properties for 1 and 2, respectively, which indicates that there should be a rapid exchange equilibrium between the protonated and deprotonated species in solutions.

Confined Synthesis of Amorphous Al2 O3 Framework Nanocomposites Based on the Oxygen-Potential Diagram as Sulfur Hosts for Catalytic Conversion.

Sulfur cathodes in Li-S batteries suffer significant volumetric expansion and lack of catalytic activity for polysulfide conversion. In this study, a confined self-reduction synthetic route is developed for preparing nanocomposites using diverse metal ions (Mn2+ , Co2+ , Ni2+ , and Zn2+ )-introduced Al-MIL-96 as precursors. The Ni2+ -introduced Al-MIL-96-derived nanocomposite contains a "hardness unit", amorphous aluminum oxide framework, to restrain the volumetric expansion, and a "softness unit", Ni nanocrystals, to improve the catalytic activity. The oxygen-potential diagram theoretically explains why Ni2+ is preferentially reduced. Postmortem microstructure characterization confirms the suppressive volume expansion. The in situ ultraviolet-visible measurements are performed to probe the catalytic activity of polysulfide conversion. This study provides a new perspective for designing nanocomposites with "hardness units" and "softness units" as sulfur or other catalyst hosts.

Heterostructure of polyoxometalate/zinc-iron-oxide nanoplates as an outstanding bifunctional electrocatalyst for the hydrogen and oxygen evolution reaction.

Electrocatalysts play an important role to increase the energy conversion efficiency of electrolysis processes. In this study, a heterostructure of zinc iron oxide (ZnFe2O4) and polyoxometalate (POM) nanoplates (POM-ZnFe2O4) was fabricated for the first time by a hydrothermal process. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) analysis of POM-ZnFe2O4 furnished low overpotentials of 268 and 356 mV, and 220 and 290 mV to achieve current densities of 20 and 50 mA cm-2, respectively. In addition, an electrolytic cell composed of a POM-ZnFe2O4 cathode and anode required an operating voltage of 1.53 V to deliver a current of 10 mA cm-2. The improved electrochemical performance of POM-ZnFe2O4 compared to commercial and recently reported catalysts is attributed to the high electrocatalytically active surface area, modulation in the electronic and chemical properties and the formation of heterojunction of ZnFe2O4 and POM, which are vital for accelerating HER and OER activity.

Three-dimensional nano assembly of nickel cobalt sulphide/polyaniline@polyoxometalate/reduced graphene oxide hybrid with superior lithium storage and electrocatalytic properties for hydrogen evolution reaction.

Engineering hierarchical nanostructures with enhanced charge storage capacity and electrochemical activity are vital for the advancement of energy devices. Herein, a highly ordered mesoporous three-dimensional (3D) nano-assembly of Nickel Cobalt Sulphide/Polyaniline @Polyoxometalate/Reduced Graphene Oxide (NiCo2S4/PANI@POM/rGO) is prepared first time via a simple route of oxidative polymerization followed by a hydrothermal method. Morphological analysis of the resulting hybrid reveals the sheet-like structures containing a homogeneous assembly of PANI@POM and NiCo2S4 on the graphene exterior maintaining huge structural integrity, large surface area and electrochemically active centres. The electrochemical analysis of the nanohybrid as the anode of the lithium-ion battery (LIB) has delivered ultra-huge reversible capacity of 735.5 mA h g-1 (0.1 A g-1 after 200 cycles), superb capacity retention (0.161% decay/per cycle at 0.5 A g-1 for 1000 cycles), and significant rate capability (355.6 mA h g-1 at 2 A g-1). The hydrogen evolution reaction (HER) measurement also proves remarkable activity, extremely low overpotential and high durability. The extraordinary performance of the nanohybrid is due to the presence of abundant electroactive centres, high surface area and a large number of ion exchange channels. These outstanding results prove the advantages of a combination of NiCo2S4, graphene sheets, and PANI@POM in energy devices.

Wide-Temperature-Range Li-S Batteries Enabled by Thiodimolybdate [Mo2S12]2- as a Dual-Function Molecular Catalyst for Polysulfide Redox and Lithium Intercalation.

In lithium-sulfur batteries, a serious obstacle is the dissolution and diffusion of long-chain polysulfides, resulting in rapid capacity decay and low Coulombic efficiency. At present, a common practice is designing cathode materials to solve this problem, but this gives rise to reduced gravimetric and volumetric energy densities. Herein, we present a thiodimolybdate [Mo2S12]2- cluster as sulfur host material that can effectively confine the shuttling of polysulfides and contribute its own capacity in Li-S cells. Moreover, the [Mo2S12]2- cluster as a "bidirectional catalyst" can effectively catalyze polysulfide reduction and lithium sulfide oxidation. We further investigate the catalytic mechanism of [Mo2S12]2- clusters by theoretical calculations, in situ spectroscopic techniques, and electrochemical studies. The (NH4)2Mo2S12/S cathodes show good electrochemical performance under a wide range of temperatures. In addition, a pouch cell fabricated with (NH4)2Mo2S12/S cathodes maintains a stable output for more than 50 cycles.

Lanthanoid-containing open Wells-Dawson silicotungstates: synthesis, crystal structures, and properties.

Five novel lanthanoid-containing silicotungstates with polymeric crystal structures [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](n)(10n-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](n)(10n-) were obtained from the one-step reaction of Na(10)[SiW(9)O(34)]·nH(2)O with Ln(NO(3))(3)·nH(2)O in a sodium acetate buffer. The compounds were characterized by single-crystal X-ray diffraction and a wide range of analytical methods, including FT-IR, UV/vis, and photoluminescence spectroscopy as well as electrochemistry and thermogravimetric analysis. This new polyoxotungstate series is the first example of lanthanoids embedded in the open Wells-Dawson silicotungstate anion [α-Si(2)W(18)O(66)](16-). The lanthanoid-containing Wells-Dawson-type polyoxoanions [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](10-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](10-) are linked by Ln(3+) cations to form 3D architectures for Gd-1 or 2D frameworks for the isostructural compounds Tb-2, Dy-2, Ho-2, and Gd-2. The structure-directing influence of the lanthanoid cation on the local structure of the dimeric building blocks and on the crystal packing motifs is investigated in detail. The photoluminescence properties of Tb-2 and Dy-2 were investigated at room temperature, and Ho-2 exhibits an interesting photochromic behavior. The magnetic susceptibility of Gd-1 and Gd-2 was studied in the temperature range between 2 and 300 K for its effective magnetic moment.

Self-Assembled Polyoxometalate Nanodots as Bidirectional Cluster Catalysts for Polysulfide/Sulfide Redox Conversion in Lithium-Sulfur Batteries.

Polyoxometalates (POMs) are a class of discrete molecular inorganic metal-oxide clusters with reversible multielectron redox capability. Taking advantage of their redox properties, POMs are thus expected to be directly involved in the lithium-sulfur batteries (Li-S, LSBs) system as a bidirectional molecular catalyst. Herein, we design a three-dimensional porous structure of reduced graphene-carbon nanotube skeleton supported POM catalyst as a high-conductive and high-stability host material. Based on various spectroscopic techniques and in situ electrochemical studies together with computational methods, the catalytic mechanism of POM clusters in Li-S battery was systematically clarified at the molecular level. The constructed POM-based sulfur cathode delivers a reversible capacity 1110 mAh g-1 at 1.0 C and cycling stability up to 1000 cycles at 3.0 C. Furthermore, Li-S pouch/beaker batteries with a POM-based cathode were successfully demonstrated. This work provides essential inputs to promote molecular catalyst design and its application in LSBs.

Exploring Anticancer Activities and Structure-Activity Relationships of Binuclear Oxidovanadium(IV) Complexes.

Dimeric mixed-ligand oxidovanadium complexes [V2O2(1,3-pdta)(bpy)2]·9H2O (1) and [V2O2(1,3-pdta)(phen)2]·6H2O (2) feature a symmetric binuclear structure bridged by 1,3-pdta, which is different from our previous reported asymmetric binuclear complex [V2O2(edta)(phen)2]·11H2O (3).In this study, a wide range of analytical techniques were carried out to fully characterize the complexes 1 and 2 and further investigate their structural stabilities. Density functional theory calculations of 1 and 2 also suggest that they might have good reactivity with biomolecules as anticancer agents. To assess and screen the antitumor activities of compounds 1-3 together with their four corresponding monomeric complexes [VO(ida)(phen)], [VO(ida)(bpy)], [VO(OH)(phen)2]Cl, and [VO(Hedta)]-, we have performed in vitro experiments with hepatocellular carcinoma HepG2 and SMMC-7721 cell lines by MTT analyses. Complex 2 was found to have the highest inhibitory potency against the growth of HepG2 and SMMC-7721 cells (IC50 = 2.07 ± 0.72 µM for HepG2; 13.00 ± 3.06 µM for SMMC-7721) compared to other compounds. The structure-activity relationship studies showed that the antitumor effect of compound 2 is higher than that of other compounds. After studying the monomeric compounds of 1-3, their effects were also ranked. Moreover, complex 2 displayed stronger binding affinity toward calf thymus DNA (Kb = 5.71 × 104 M-1) and cleavage activities than the other complexes (Kb = 1.34 × 104 M-1 for 1 and 5.22 × 104 M-1 for 3, respectively). We further extended the cellular mechanisms of drug action and found that 2 could block DNA synthesis and cell division of HepG2 and 7721 cells and further induce apoptosis by flow cytometry assays. In short, these results indicate that binuclear oxidovanadium compounds could have potential as simple, effective, and safe antitumor agents.

Correction: Transition metal substituted sandwich-type polyoxometalates with a strong metal-C (imidazole) bond as anticancer agents.

Correction for 'Transition metal substituted sandwich-type polyoxometalates with a strong metal-C (imidazole) bond as anticancer agents' by Hongxia Zhao et al., Chem. Commun., 2019, 55, 1096-1099.