Polyoxometalate exerts broad-spectrum activity against human respiratory viruses hampering viral entry.

Human respiratory viruses have an enormous impact on national health systems, societies, and economy due to the rapid airborne transmission and epidemic spread of such pathogens, while effective specific antiviral drugs to counteract infections are still lacking. Here, we identified two Keggin-type polyoxometalates (POMs), [TiW11CoO40]8- (TiW11Co) and [Ti2PW10O40]7- (Ti2PW10), endowed with broad-spectrum activity against enveloped and non-enveloped human respiratory viruses, i.e., coronavirus (HCoV-OC43), rhinovirus (HRV-A1), respiratory syncytial virus (RSV-A2), and adenovirus (AdV-5). Ti2PW10 showed highly favorable selectivity indexes against all tested viruses (SIs >700), and its antiviral potential was further investigated against human coronaviruses and rhinoviruses. This POM was found to inhibit replication of multiple HCoV and HRV strains, in different cell systems. Ti2PW10 did not affect virus binding or intracellular viral replication, but selectively inhibited the viral entry. Serial passaging of virus in presence of the POM revealed a high barrier to development of Ti2PW10-resistant variants of HRV-A1 or HCoV-OC43. Moreover, Ti2PW10 was able to inhibit HRV-A1 production in a 3D model of the human nasal epithelium and, importantly, the antiviral treatment did not determine cytotoxicity or tissue damage. A mucoadhesive thermosensitive in situ hydrogel formulation for nasal delivery was also developed for Ti2PW10. Overall, good biocompatibility on cell lines and human nasal epithelia, broad-spectrum activity, and absence of antiviral resistance development reveal the potential of Ti2PW10 as an antiviral candidate for the development of a treatment of acute respiratory viral diseases, warranting further studies to identify the specific target/s of the polyanion and assess its clinical potential.

Discrete Platinum(II/IV)-Arsenito Clusters with Pt-As and Pt-O Bonding: [PtIV(As3O6)2]2-, [Pt4II(H2AsO3)6(HAsO3)2]2-, and [Pt2IIAs6W4O28]10.

The first two discrete, fully inorganic platinum(II/IV)-arsenito clusters, [fac-PtIV(As3O6)2]2- (PtAs6) and [Pt4II(H2AsO3)6(HAsO3)2]2- (Pt4As8), as well as the platinum(II)-arsenito heteropolytungstate [Pt2IIAs6W4O28]10- (Pt2As6W4), have been synthesized in aqueous media using simple one-pot reaction conditions. In PtAs6, a PtIV ion is coordinated to two cyclic, tridentate As3O6 units via oxo-donation (PtIV-O ∼ 2.02 Å). In Pt4As8, each PtII ion is coordinated to four AsO3 ligands via two oxygens and two AsIII atoms in a square-planar fashion (PtII-AsIII 2.31 Å, PtII-O 2.07 Å), resulting in an open cage-like structure, which forms a strong tetrameric assembly in the solid state mediated by two K+ counterions. In Pt2As6W4, each PtII ion is coordinated by the As atoms of three AsO3 ligands (PtII-AsIII 2.38 Å) and an oxo group (PtII-O 2.07 Å) in addition to bridging two tungsten ions, and this polyanion was characterized in solution by 195Pt NMR.

Gallium(III)- and Thallium(III)-Encapsulated Polyoxopalladates: Synthesis, Structure, Multinuclear NMR, and Biological Activity Studies.

Three gallium(III)- and thallium(III)-containing polyoxopalladates (POPs) have been synthesized and structurally characterized in the solid state and in solution, namely, the phosphate-capped 12-palladate nanocubes [XPd12O8(PO4)8]13- (X = GaIII, GaPd12P8; X = TlIII, TlPd12P8) and the 23-palladate double-cube [Tl2IIIPd23P14O70(OH)2]20- (Tl2Pd23P14). The cuboid POPs, GaPd12P8 and TlPd12P8, are solution stable as verified by the respective 31P, 71Ga, and 205Tl nuclear magnetic resonance (NMR) spectra. Of prime interest, the spin-spin coupling schemes allowed for an intimate study of the solution behavior of the TlIII-containing POPs via a combination of 31P and 205Tl NMR, including the stoichiometry of the major fragments of Tl2Pd23P14. Moreover, biological studies demonstrated the antitumor and antiviral activity of GaPd12P8 and TlPd12P8, which were validated to be as efficient as cis-platinum against human melanoma and acute promyelocytic leukemia cells. Furthermore, GaPd12P8 and TlPd12P8 exerted inhibitory activity against two herpetic viruses, HSV-2 and HCMV, in a dose-response manner.

PtIV-Containing Hexaplatinate(II) [PtIVPtII6O6(AsO2(CH3)2)6]2- and Hexapalladate(II) [PtIVPdII6O6(AsO2(CH3)2)6]2.

The first PtIV-containing discrete polyoxoplatinate(II) [PtIVPtII6O6(AsO2(CH3)2)6]2- (Pt7) and polyoxopalladate(II) [PtIVPdII6O6(AsO2(CH3)2)6]2- (PtPd6) have been prepared and characterized in the solid state, in solution, and in the gas phase. The molecular structures of the noble metal-oxo clusters Pt7 and PtPd6 comprise a central, octahedral PtIVO6 hetero group surrounded by six square-planar MO4 (M = PtII, PdII) units, which are capped by six dimethylarsinate ligands. The polyanions were prepared under simple one-pot aqueous solution conditions by reacting H2Pt(OH)6 with either K2PtCl4 or Pd(NO3)2 in sodium dimethylarsinate buffer (pH 7) at 80 °C. Catalytic studies were performed on Pt7 supported on SBA15-apts for o-xylene hydrogenation at 300 °C and 90 bar H2 pressure and indicated excellent activity and recyclability with low activation temperature.

Mixed noble metal-oxo clusters: platinum(IV)-gold(III) oxoanion [PtIV2AuIII3O6((CH3)2AsO2)6].

The first discrete mixed platinum(IV)-gold(III) oxoanion [PtIV2AuIII3O6((CH3)2AsO2)6]- (1) was synthesized by reaction of H2Pt(OH)6 with H[AuCl4] in a simple one-pot procedure in aqueous solution at pH 7 and comprises two equivalent PtIVO6(As(CH3)2)3 units which are linked by three square-planar AuIIIO4 units. Polyanion 1 could be isolated as a potassium or sodium salt in good yield, which were structurally characterized in the solid state by single-crystal XRD and TGA, and in solution by multinuclear (1H, 13C, 195Pt) NMR, indicating that polyanion 1 is stable in solution, which was confirmed by ESI-MS studies. The sodium salt of 1 undergoes a clean single-crystal-to-single-crystal (SCSC) structural transformation upon rehydration and dehydration.

Mixed-valent palladium(IV/II)-oxoanion, [PdIVO6PdII6((CH3)2AsO2)6]2.

We report on the first example of a PdIV-containing polyoxopalladate(II). The discrete mixed-valent polyoxopalladate(IV/II), [PdIVPdII6O6((CH3)2AsO2)6]2-, comprising a central PdIV ion that is surrounded by a six-membered PdII-oxo ring capped by six dimethylarsinate groups, was synthesized and structurally characterized in the solid state, in solution and in the gas phase by multiple analytical techniques.

Discrete Arsonate-Grafted Inverted-Keggin 12-Molybdate Ion [Mo12O32(OH)2(4-N3C2H2-C6H4AsO3)4]2- and Formation of a Copper(II)-Mediated Metal-Organic Framework.

The discrete inverted-Keggin ion [Mo12O32(OH)2(4-N3C2H2-C6H4AsO3)4]2- (1) has been prepared in an aqueous acidic (pH 0.8) medium by the reaction of MoO3 with the (4-triazolylphenyl)arsonic acid 4-N3C2H2-C6H4AsO3H2 under hydrothermal conditions and was isolated as a sodium salt in 21% yield. The exact same reaction in the presence of Cu2+ ions resulted in the neutral metal-organic framework (MOF) Cu2[Mo12O34(4-N3C2H2-C6H4AsO3)4] (Cu-1) in 68% yield. The inverted-Keggin ion 1 comprises a metal-oxo core, which is capped by four organoarsonate groups, and in Cu-1, individual polyanions are linked in the solid state by coordination of the Cu2+ ions with the triazolyl groups. The discrete ion 1 was characterized by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic absorption (AA) spectroscopy, as well as thermogravimetric analysis (TGA), and the POM-MOF Cu-1 was characterized by single-crystal and powder XRD, FT-IR, TGA, and gas sorption. Cu-1 has channels with a diameter of around ∼0.9 nm and exhibits a water-vapor adsorption capacity of 89.7 cm3 g-1 (p/p0 = 0.95).

Host-Guest Chemistry in Discrete Polyoxo-12-Palladate(II) Cubes [MO8Pd12L8]n- (M = ScIII, CoII, CuII, L = AsO43 -; M = CdII, HgII, L = PhAsO32-): Structure, Magnetism, and Catalytic Hydrogenation.

A family of five host-guest assemblies comprising different metal ions inside a cuboid 12-palladium-oxo cage, [MO8Pd12L8]n- (MPd12L8, M = ScIII, CoII, CuII, L = AsO43-; M = CdII, HgII, L = PhAsO32-), was synthesized and structurally characterized in the solid state by single-crystal X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis, and their solution and gas-phase stability were validated by multinuclear NMR spectroscopy and electrospray-ionization mass spectrometry (ESI-MS). The polyoxopalladates (POPs) ScPd12As8, CoPd12As8, and CuPd12As8 represent the first three examples of the MPd12As8 archetype. The unique cubic ligand field of {MO8} allows for collecting the speciation profiles of the POPs in solution using 45Sc and 113Cd NMR techniques. Detailed magnetic and electron paramagnetic resonance (EPR) studies were performed on CuPd12As8. Catalytic studies on MPd12As8 (M = CuII and CoII) supported on SBA-15 unveiled a guest metal-dependent structure-function relationship, with CuPd12As8 being the more efficient precatalyst for the hydroconversion of o-xylene in a fixed-bed reactor.

Organically Functionalized Mixed-Valent Polyoxo-30-molybdate Wheel and Neutral Tetramolybdenum(V) Oxo Cluster.

The first organofunctionalized mixed-valent polyoxo-30-molybdate wheel, [MoVI18MoV12O84{AsO2(CH3)2}18]18- (Mo30), was synthesized in aqueous, mildly acidic conditions, and upon further acidification, the neutral tetramolybdenum(V) oxo cluster [MoV4O8{AsO2(CH3)2}4] (Mo4) was obtained. Single-crystal X-ray diffraction (XRD) revealed that Mo30 comprises 18 MoVI and 12 MoV ions arranged in a cyclic fashion with alternating {MoV2} and {MoVI3} groups, which are capped by 18 dimethylarsinate ligands, resulting in a novel polyoxo-30-molybdate wheel with a central cavity of ∼1.5 nm. On the other hand, Mo4 has a distorted-cubic structure, with the corners of the cube being occupied by alternating MoV ions and oxo ligands. The compounds were characterized in solution by 1H and 13C NMR and UV-vis spectroscopy and in the solid state by X-ray photoelectron spectroscopy and powder XRD. Mo30 represents a novel type of polyanionic cycle with manyfold possibilities regarding host-guest chemistry.

Discovery of Polythioplatinate(II) [Pt3S2(SO3)6]10- and Study of Its Solution and Catalytic Properties.

We have discovered the first polythioplatinate(II), [PtII3S2(SO3)6]10- (1), which was synthesized in aqueous basic medium (pH 11) by hydrothermal heating at 150 °C. Polyanion 1 comprises a discrete, triangular assembly of three Pt2+ ions linked by two µ3-sulfido ligands, and their square-planar coordination geometry is completed by two terminal S-bound sulfito ligands. Polyanion 1 was isolated as a hydrated sodium salt, Na10[PtII3(µ3-S)2(SO3)6]·22H2O (Na-1), which was characterized in the solid state by single-crystal X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectra, and elemental analysis, in solution by 195Pt NMR and atomic absorption spectroscopy, and in the gas phase by electrospray ionization mass spectrometry. Density functional theory calculations were performed, and the 195Pt NMR chemical shifts of 1 were computed theoretically and shown to match well with the experimental data. Furthermore, the discrete title polyanion 1 was immobilized on mesoporous SBA-15 support and used as a precatalyst for the hydrogenation of o-xylene.

Discrete, Cationic Palladium(II)-Oxo Clusters via f-Metal Ion Incorporation and their Macrocyclic Host-Guest Interactions with Sulfonatocalixarenes.

We report on the discovery of the first two examples of cationic palladium(II)-oxo clusters (POCs) containing f-metal ions, [PdII6 O12 M8 {(CH3 )2 AsO2 }16 (H2 O)8 ]4+ (M=CeIV , ThIV ), and their physicochemical characterization in the solid state, in solution and in the gas phase. The molecular structure of the two novel POCs comprises an octahedral {Pd6 O12 }12- core that is capped by eight MIV ions, resulting in a cationic, cubic assembly {Pd6 O12 MIV8 }20+ , which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed PdII -CeIV /ThIV oxo-clusters [PdII6 O12 M8 {(CH3 )2 AsO2 }16 (H2 O)8 ]4+ (M=Ce, Pd6 Ce8 ; Th, Pd6 Th8 ). We have also studied the formation of host-guest inclusion complexes of Pd6 Ce8 and Pd6 Th8 with anionic 4-sulfocalix[n]arenes (n=4, 6, 8), resulting in the first examples of discrete, enthalpically-driven supramolecular assemblies between large metal-oxo clusters and calixarene-based macrocycles. The POCs were also found to be useful as pre-catalysts for electrocatalytic CO2 -reduction and HCOOH-oxidation.

Organorhodium(III)- and Iridium(III)-Substituted 20-Tungstobismuthates(III) and -Antimonates(III), [(MCp*)2X2W20O70]10- (M = RhIII and IrIII; X = BiIII and SbIII).

The synthesis of four organometallic RhCp*- and IrCp*-containing heteropoly-20-tungstates, [{RhCp*}2Bi2W20O70]10- (1), [{IrCp*}2Bi2W20O70]10- (2), [{RhCp*}2Sb2W20O70]10- (3), and [{IrCp*}2Sb2W20O70]10- (4) has been accomplished by reaction of (MCp*Cl2)2 with [X2W22O74(OH)2]12- in aqueous solution at pH 6 and 70 °C. The four polyanions 1-4 were structurally characterized in the solid state by single-crystal XRD, FTIR, and TGA and in solution by 183W and 13C NMR. For the Rh derivatives 1 and 3 the 183W-103Rh coupling (2 J W-Rh 3.0 Hz) could be identified by 183W NMR.

Discovery of a Neutral 40-PdII-Oxo Molecular Disk, [Pd40O24(OH)16{(CH3)2AsO2}16]: Synthesis, Structural Characterization, and Catalytic Studies.

We report on the synthesis and structural characterization of a giant, discrete, and neutral molecular disk, [Pd40O24(OH)16{(CH3)2AsO2}16] (Pd40), comprising a 40-palladium-oxo core that is capped by 16 dimethylarsinate moieties, resulting in a palladium-oxo cluster (POC) with a diameter of ∼2 nm. Pd40, which is the largest known neutral Pd-based oxo cluster, can be isolated either as a discrete species or constituting a 3D H-bonded organic-inorganic framework (HOIF) with a 12-tungstate Keggin ion, [SiW12O40]4- or [GeW12O40]4-. 1H and 13C NMR as well as 1H-DOSY NMR studies indicate that Pd40 is stable in aqueous solution, which is also confirmed by ESI-MS studies. Pd40 was also immobilized on a mesoporous support (SBA15) followed by the generation of size-controlled Pd nanoparticles (diameter ∼2-6 nm, as based on HR-TEM), leading to an effective heterogeneous hydrogenation catalyst for the transformation of various arenes to saturated carbocycles.

Metallodrug Profiling against SARS-CoV-2 Target Proteins Identifies Highly Potent Inhibitors of the S/ACE2 interaction and the Papain-like Protease PLpro.

The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for dedicated antiviral therapeutics. Metal complexes are commonly underrepresented in compound libraries that are used for screening in drug discovery campaigns, however, there is growing evidence for their role in medicinal chemistry. Based on previous results, we have selected more than 100 structurally diverse metal complexes for profiling as inhibitors of two relevant SARS-CoV-2 replication mechanisms, namely the interaction of the spike (S) protein with the ACE2 receptor and the papain-like protease PLpro . In addition to many well-established types of mononuclear experimental metallodrugs, the pool of compounds tested was extended to approved metal-based therapeutics such as silver sulfadiazine and thiomersal, as well as polyoxometalates (POMs). Among the mononuclear metal complexes, only a small number of active inhibitors of the S/ACE2 interaction was identified, with titanocene dichloride as the only strong inhibitor. However, among the gold and silver containing complexes many turned out to be very potent inhibitors of PLpro activity. Highly promising activity against both targets was noted for many POMs. Selected complexes were evaluated in antiviral SARS-CoV-2 assays confirming activity for gold complexes with N-heterocyclic carbene (NHC) or dithiocarbamato ligands, a silver NHC complex, titanocene dichloride as well as a POM compound. These studies might provide starting points for the design of metal-based SARS-CoV-2 antiviral agents.

Selected polyoxopalladates as promising and selective antitumor drug candidates.

Polyoxo-noble-metalates (PONMs), a class of molecular noble metal-oxo nanoclusters that combine features of both polyoxometalates and noble metals, are a promising platform for the development of next-generation antitumor metallodrugs. This study aimed to evaluate the antitumor potential against human neuroblastoma cells (SH-SY5Y), as well as toxicity towards healthy human peripheral blood cells (HPBCs), of five polyoxopalladates(II): (Na8[Pd13As8O34(OH)6]·42H2O (Pd13), Na4[SrPd12O6(OH)3(PhAsO3)6(OAc)3]·2NaOAc·32H2O (SrPd12), Na6[Pd13(AsPh)8O32]·23H2O (Pd13L), Na12[SnO8Pd12(PO4)8]·43H2O (SnPd12), and Na12[PbO8Pd12(PO4)8]·38H2O (PbPd12)), as the largest subset of PONMs. A pure inorganic, Pd13, was found as the most potent and selective antineuroblastoma agent with IC50 values (µM) of 7.2 ± 2.2 and 4.4 ± 1.2 for 24 and 48 h treatment, respectively, even lower than cisplatin (28.4 ± 7.4 and 11.6 ± 0.8). The obtained IC50 values (µM) for 24/48 h treatment with SrPd12 and Pd13L were 75.8 ± 6.7/76.7 ± 22.9 and 63.8 ± 3.6/21.4 ± 10.8, respectively, whereas SnPd12 and PbPd12 did not remarkably affect the SH-SY5Y viability (IC50 > > 100 µM). Pd13 caused depolarisation of inner mitochondrial membrane prior to superoxide ion hyperproduction, followed by caspase activation, DNA fragmentation and cell cycle arrest, all hallmarks of apoptotic cell death, and accompanied by an increase in acidic vesicles content, suggestive of autophagy induction. Importantly, Pd13 demonstrated the antitumor effect at concentrations not cytogenotoxic for normal HPBCs. On the contrary, SrPd12 and Pd13L at concentrations ≥ 1/3 IC50 (24 h) decreased HPBC viability and increased % tail DNA up to 42% and 3.05 times, respectively, related to control. SnPd12 and PbPd12, previously confirmed promising antileukemic agents, did not exhibit cytogenotoxicity to HPBCs, and thus could be regarded as tumor cell specific and selective drug candidates.

NiII 36 -Containing 54-Tungsto-6-Silicate: Synthesis, Structure, Magnetic and Electrochemical Studies.

The 36-NiII -containing 54-tungsto-6-silicate, [Ni36 (OH)18 (H2 O)36 (SiW9 O34 )6 ]6- (Ni36 ) was synthesized by a simple one-pot reaction of the Ni2 -pivalate complex [Ni2 (µ-OH2 )(O2 CCMe3 )4 (HO2 CCMe3 )4 ] with the trilacunary [SiW9 O34 ]10- polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII 6 SiW9 } units which are linked by Ni-O-W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6 } building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6 } units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple.

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M2(AsIIIW6O25)2(AsIIIOH)x]n- (M = CrIII, FeIII, ScIII, InIII, TiIV, MnII) and Their Magnetic Properties.

Six arsenic(III)-capped 12-tungsto-2-arsenates(III) of the type [M2(AsIIIW6O25)2(AsIIIOH)x]n- (M = CrIII, 1; FeIII, 2; ScIII, 3; InIII, 4; TiIV, 5; MnII, 6) have been synthesized in aqueous medium by direct reaction of the elements using a one-pot strategy and structurally characterized by FT-IR spectroscopy, single-crystal XRD, and elemental analysis. Polyanions 1-6 are comprised of two octahedrally coordinated guest metal ions M sandwiched between two {AsW6} units, resulting in a structure with C2h point-group symmetry. Polyanions 1-5 contain tri- and tetravalent metal ion guests M (M = CrIII, FeIII, ScIII, InIII, and TiIV, respectively), and they have one {AsIIIOH} group grafted on each {AsW6} unit, whereas the divalent MnII-containing derivative 6 has two such {AsIIIOH} groups grafted on each {AsW6} unit. Magnetic studies on polyanions 3-5 over the temperature range 1.8-295 K and magnetic fields of 0-7 T confirmed that they are diamagnetic. On the other hand, polyanions 1, 2, and 6 are strongly magnetic and follow the Curie-Weiss law above 30 K. The susceptibility plots of 1 and 6 exhibit broad peaks suggesting short-range antiferromagnetic ordering, while the very weak antiferromagnetic ordering of 2 is overshadowed by traces of a paramagnetic impurity. The magnetization data of 1, 2, and 6 at 1.8 K over 0-7 T were analyzed by using the Heisenberg exchange procedure. Small (negative) values of the obtained J values help in understanding the absence of long-range antiferromagnetic ordering.

Arylarsonate- and Phosphonate-Capped Polyoxomolybdates, [(RC6H4As)2Mo6O24]n- and [(R'C6H4P)2Mo5O21]n.

We report on the synthesis and structural characterization of four arylarsonate- and phosphonate-capped polyoxomolybdates that exhibit different organic substituents in the para position of the phenyl group. The reaction of arylarsonates (RAsO3, wherein R = 4-BrC6H4 or 4-N3C6H4) with molybdate in aqueous pH 3.5 media resulted in the cyclic hexamolybdates [(BrC6H4As)2Mo6O24]4- (Mo6As2La) and [(N3C6H4As)2Mo6O24]4- (Mo6As2Lb), whereas the reaction of arylphosphonates (R'PO3, wherein R' = 4-O2CC6H4 or 4-O2CC6H4CH2) with molybdate in aqueous pH 3 media resulted in the cyclic pentamolybdates [(O2CC6H4P)2Mo5O21]6- (Mo5P2Lc) and [(HO2CC6H4CH2P)2Mo5O21]4- (Mo5P2Ld), respectively. Polyanions Mo6As2La and Mo6As2Lb comprise a ring of six MoO6 octahedra that is capped on either side by an organoarsonate group, whereas Mo5P2Lc and Mo5P2Ld consist of a ring of five MoO6 octahedra that is capped on either side by an organophosphonate group, with the organic arms protruding away from the metal-oxo core of the polyanions. All four polyanions Mo6As2La, Mo6As2Lb, Mo5P2Lc, and Mo5P2Ld have been characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analysis and in solution by multinuclear NMR (31P, 13C, and 1H). The synthetic procedure of (4-bromophenyl)arsonic acid, BrC6H4AsO3H2, is reported here for the first time.

Synthesis, structure, electrochemistry and magnetism of cobalt-, nickel- and zinc-containing [M4(OH)3(H2O)2(α-SiW10O36.5)2]13- (M = Co2+, Ni2+, and Zn2+).

Interaction of the trilacunary 9-tungstosilicate [A-α-SiW9O34]10- with cobalt(ii), nickel(ii) and zinc(ii) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M4-containing heteropolytungstates [M4(OH)3(H2O)2(α-SiW10O36.5)2]13- (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the WVI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction.

PtIV- or MoVI-substituted decavanadates inhibit the growth of Mycobacterium smegmatis.

Inhibitory effects of two monosubstituted decavanadates by PtIV in monoplatino(IV)nonavanadate(V) ([H2PtIVV9O28]5-, V9Pt), and by MoIV in monomolybdo(VI)nonavanadate(V) ([MoVIV9O28]5-,V9Mo) were investigated against the growth of Mycobacterium smegmatis with the EC50 values of 0.0048 mM and 0.015 mM, respectively. These compare to the reported inhibitory value for decavanadate ([V10O28]6-/[HV10O28]5-, V10) on Mycobacterium smegmatis (EC50 = 0.0037 mM). Time-dependent 51V NMR spectroscopic studies were carried out for all three polyanions in aqueous solution, biological medium (7H9), heated and non-heated supernatant to evaluate their stability in their respective media, monitor their hydrolysis to form various oxovanadates over time and calculate the EC50 values. These studies allow us to calculate adjusted and maximum EC50 for the polyoxovanadate (POV) present in solution at the beginning of the study when there is most intact anion in the media and thus the EC50 values represent the initial effects of the POVs. The results have shown that V10 is 1.3 times more potent than V9Pt and 4 times more potent than V9Mo, indicating that the inhibitory effects of monosubstituted polyanions are related to the V10 structure. We attributed the minor differences in the growth inhibitory effects to the differences in charges (5- vs 6-) of V9Pt and V9Mo compared to V10 and/or the differences in the chemical composition. We concluded that the potency of the growth inhibition by V10 is mainly due to the chemical properties of the vanadium and the decametalate's unique structure even though the presence of the Mycobacterium smegmatis facilitate hydrolysis of the anions. SYNOPSIS: Two decavanadate derivatives, monoplatino(IV)nonavanadate(V) ([H2PtIVV9O28]5-), monomolybdo(VI)nonavanadate(V) ([MoVIV9O28]5-) and decavanadate are more potent growth inhibitors of Mycobacterium smegmatis than monomeric vanadate. The spectroscopic characterization carried out in the growth medium led to the conclusion that both the decavanadate structure and its properties are important for its growth effects.