Polyoxometalate inhibition of SOX2-mediated tamoxifen resistance in breast cancer.

Background: Increased cancer stem cell (CSC) content and SOX2 overexpression are common features in the development of resistance to therapy in hormone-dependent breast cancer, which remains an important clinical challenge. SOX2 has potential as biomarker of resistance to treatment and as therapeutic target, but targeting transcription factors is also challenging. Here, we examine the potential inhibitory effect of different polyoxometalate (POM) derivatives on SOX2 transcription factor in tamoxifen-resistant breast cancer cells.

Effect of the heteroatom on the magnetic and luminescence properties of hybrid lanthanide-substituted Keggin-type polyoxometalates.

Replacement of the heteroatom from Si to Ge has a strong influence on the luminescence properties of a series of hybrid, sandwich-type K[Ln(α-GeWO)(CHBrNO)]·14HO (1Ge-Ln, Ln = Sm to Lu) anions. Interestingly, the Gd and Yb derivatives retain their ability to display slow relaxation of magnetisation.

Crystal-to-crystal polymerisation of monosubstituted [PWOCu(HO)] Keggin-type anions.

The reaction between neutral bis(picolinate)copper(II) complexes and copper(II)-monosubstituted Keggin-type phosphotungstate anions formed leads to the formation of the hybrid [C(NH)][{PWOCu(HO)}{Cu(pic)}]·10HO compound (1, pic = picolinate) in the presence of structure-directing guanidinium cations. Single-crystal X-ray diffraction studies demonstrate that 1 contains dimeric {PWOCu(HO)}{Cu(pic)} molecular species constituted by two Keggin-type anions linked by one {Cu(pic)} octahedral complex through axial coordination to their terminal oxygen atoms. The extensive hydrogen-bonding network established by guanidium cations and Keggin clusters plays a key role in retaining the crystallinity of the system throughout dehydration to allow a single-crystal-to-single-crystal (SCSC) transformation into the anhydrous [C(NH)][{PWOCu}{Cu(pic)}] (2a) at 170 °C.

Systematic Approach to the Synthesis of Cobalt-Containing Polyoxometalates for Their Application as Energy Storage Materials.

New energy storage materials are an object of study within the framework of the global energy transition. The development of renewable sources is being boosted thanks to stationary energy storage systems such as redox flow batteries (RFBs). This work reports the synthesis of the cobalt-containing Keggin-type polyoxometalates [CoWO] () and [Co(HO)SiWO] (), which have previously been shown to have applicability in RFBs.

Consecutive Single-Crystal-to-Single-Crystal Isomerization of Novel Octamolybdate Anions within a Microporous Hybrid Framework with Robust Water Sorption Properties.

The 3D hybrid framework [{Cu(cyclam)} (κ-Mo O )] ⋅ 14H O (1) (cyclam=1,4,8,11-tetraazacyclotetradecane) undergoes sequential single-crystal-to-single-crystal transformations upon heating to afford two different anhydrous phases (2 a and 3 a). These transitions modify the framework dimensionality and enable the isomerization of κ-octamolybdate (κ-Mo ) anions into λ (2 a) and μ (3 a) forms through metal migration. Hydration of 3 a involves condensation of one water molecule to the cluster to afford the γ-Mo isomer in 4, which dehydrates back into 3 a through the 6 a intermediate.

Reversible First-Order Single Crystal to Single Crystal Thermal Phase Transition in [(CH)CNH][VO].

The well-known compound tetrakis(tert-butylammonium)-cyclo-tetrametavanadate (V), [(CH)CNH][VO] (1h_RT), which crystallizes in the tetragonal I4/m space group, undergoes an irreversible solid state transformation upon heating, constituting one of the few examples in which the initial and the final stages are structurally characterized by sc-XRD. Now, we observed the ability of the same compound to undergo an additional single-crystal-to-single-crystal (SCSC) transformation upon thermal stimuli, but this time at low temperatures (153 K). Compound 1h_RT contains a discrete unprotonated [VO] tetrahedral anion in which V and O bridging atoms are coplanar.

Slow Magnetic Relaxation and Luminescent Properties of Mononuclear Lanthanide-Substituted Keggin-Type Polyoxotungstates with Compartmental Organic Ligands.

The reaction of mid to late lanthanide ions with the ,'-dimethyl-,'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylene-diamine organic ligand and monolacunary Keggin type [α-SiWO] anion affords a series of isostructural compounds, namely, K[Ln(α-SiWO)(CHBrNO)]·14HO (-Ln, Ln = Sm to Lu). The molecular structure of these sandwich-type complexes is formed by the Ln ion in a biaugmented trigonal prismatic geometry, which occupies the external O site of the organic ligand and the vacant site of the lacunary polyoxometalate (POM) unit. The empty NO coordination site of the organic ligand allows its unprecedented folding, which displays a relative perpendicular arrangement of aromatic groups.

Single-Crystal-to-Single-Crystal Cluster Transformation in a Microporous Molybdoarsenate(V)-Metalorganic Framework.

The hybrid compound [Cu(cyclam)(HO)][{Cu(cyclam)}{-HAsMoO(HO)}]·9HO () (cyclam = 1,4,8,11-tetraazacyclotetradecane) was synthesized in aqueous solution by reacting the {Cu(cyclam)} complex with a mixture of heptamolybdate and an arsenate(V) source. Crystal packing of exhibits a supramolecular open-framework built of discrete covalent molybdoarsenate/metalorganic units and additional [Cu(cyclam)(HO)] cations, the stacking of which generates squarelike channels parallel to the axis with an approximate cross section of 10 × 11 Å where all the hydration water molecules are hosted. Thermal evacuation of solvent molecules yields a new anhydrous crystalline phase, but compound does not preserve its single-crystalline nature upon heating.

Isolation of the Elusive Heptavanadate Anion with Trisalkoxide Ligands.

The unprecedented heptavanadate cluster has been isolated from reactions between trisalkoxide ligands and vanadate in water at pH = 2 as a series of alkylammonium [HVO(HO)((OCH)CR)] salts (-, R = CHOH; , R = CH). Their structures have been determined and the partial stability of in water assessed by a combination of multinuclear NMR spectroscopy and ESI-MS. The heptavanadate unit reported herein could represent an intermediate species in the formation of decavanadate that is blocked by attachment of tripodal ligands.

Structural Characterization of Mono and Dihydroxylated Umbelliferone Derivatives.

Coumarin derivatives are a class of compounds with a pronounced wide range of applications, especially in biological activities, in the medicine, pharmacology, cosmetics, coatings and food industry. Their potential applications are highly dependent on the nature of the substituents attached to their nucleus. These substituents modulate their photochemical and photophysical properties, as well as their interactions in their crystalline form, which largely determines the final field of application.

Toward Advanced Functional Systems: Honeycomb-Like Polymeric Surfaces Incorporating Polyoxovanadates with Surface-Appended Copper-Cyclam Complexes.

In this work the immobilization of hybrid polyoxometalates (POMs) onto functional polymeric surfaces is exposed and discussed. Thus, various hybrid polymer‒inorganic films were prepared by anchoring selected hybrid POMs onto tailored polymeric surfaces that consisted of breath figures (BFs) made of polystyrene-b-poly(acrylic acid)/polystyrene (PS-b-PAA/PS) blends. Functionalization of the BF films was performed by selective arrangement of acrylic acid groups of the amphiphilic block copolymer on the surface pores because of their affinition for the water condensed during breath figure formation.

Structural Transformations in the Thermal Dehydration of [Cu(bpa)(btec)(HO)] Coordination Polymer.

Reactions between pyridinic ligands such as 1,2-bis(4-pyridyl)ethane () and transition metal cations are a very widespread technique to produce extended coordination polymers such as Metal-Organic Frameworks. In combination with a second ligand these systems could present different topologies and behaviors. In this context, the use of 1,2,4,5-benzenetetracarboxylic acid () gave us a novel 2D compound, [Cu(bpa)(btec)(HO)] (), which was prepared by microwave-assisted synthesis and structurally characterized by means of single crystal X-ray diffraction.

Chitosan nanogels as nanocarriers of polyoxometalates for breast cancer therapies.

Polyoxometalates (POMs) have been revealed as interesting antitumor agents inhibiting the action of Sox2 transcription factor, which reduces the risk of metastasis during hormonal therapies. However, they have shown serious concerns to be incorporated into the cells due to their cytotoxicity. Taking this into consideration, this study aims to develop polyoxometalate-based nanocarriers to be potentially applied as new forms of anticancer therapies.

Thermostructural Behavior in a Series of Lanthanide-Containing Polyoxotungstate Hybrids with Copper(II) Complexes of the Tetraazamacrocycle Cyclam: A Single-Crystal-to-Single-Crystal Transformation Study.

A series of 14 isostructural [Cu(cyclam)][{Cu(cyclam)}{(α-GeWO)Ln(HO)(OAc)}]·18HO (1-Ln, where Ln = La-Lu; cyclam = 1,4,8,11-tetraazacyclotetradecane) polyoxometalate-based hybrids reported herein represent (i) the first example of a two-dimensional covalent hybrid lattice involving the [{(α-XWO)Ln(HO)(OAc)}] archetype and (ii) the first structural characterization of such a dimeric polyoxotungste for Ln = La and Pr as well as for the combination of X = Ge and Ln = Ce, Nd, Sm, or Lu. Compounds 1-Ln have been characterized by elemental analyses, infrared spectroscopy, and thermogravimetric analysis, and their thermostructural behavior has been monitored by powder and single-crystal X-ray diffraction. The title compounds undergo two single-crystal-to-single-crystal transformations triggered by thermal dehydration leading to the [{Cu(cyclam)}{(α-GeWO)Ln(HO)(OAc)}]·4HO intermediate (2-Ln, where Ln = Eu or Er) and [Cu(cyclam)][{Cu(cyclam)}{(α-GeWO)Ln(OAc)}] (3-Ln, where Ln = Ce or Eu) final anhydrous phases, the latter evidencing a coordinatively unsaturated derivative of the dimeric archetype for the first time.

Six tris-(bipyrid-yl)iron(II) complexes with 2-substituted 1,1,3,3-tetra-cyano-propenide, perchlorate and tetra-fluorido-borate anions; order disorder, hydrogen bonding and C-N⋯π inter-actions.

Structures are reported for six closely related salts of tris-(bipyrid-yl)iron(II) cations, namely tris-(2,2'-bi-pyridine)-iron(II) bis-(1,1,3,3-tetra-cyano-2-meth-oxy-propenide) 0.776-hydrate, [Fe(CHN)](CHNO).0.

A Charge-Transfer Salt Based on Ferrocene/Ferrocenium Pairs and Keggin-Type Polyoxometalates.

A new hybrid inorganic-organometallic salt has been obtained from the reaction of the Keggin-type silicotungstate anion with ferrocene in a water/methanol mixture as a result of the partial oxidation of ferrocene molecules to ferrocenium cations. Single-crystal X-ray diffraction analysis reveals the presence of four ferrocenium (Fe) cations and one ferrocene (Fe) molecule per plenary Keggin anion in the crystal structure of [Fe (Cp)₂]₄[SiWO]·[Fe(Cp)₂]·2CH₃OH (). Compound thus constitutes the first example in the literature in which ferrocenium and ferrocene species coexist in the structure of a polyoxometalate-based salt.

Single-crystal-to-single-crystal transformations triggered by dehydration in polyoxometalate-based compounds.

Single-crystal-to-single-crystal transformations are solid-state phase transitions between different crystalline states in which the crystal integrity and the long-range structural order are retained through the whole transformation process. Such a phenomenon constitutes the structural response that some compounds afford when being exposed to a given external stimulus (temperature, pressure, light, etc.) and, therefore, its study has become a relevant focus of interest within crystal engineering because it allows for monitoring how certain properties (colour, magnetism, luminescence, porosity) of the stimuli-responsive material are modified as the structure evolves into the activated form.

Immobilization of Polyoxometalates on Tailored Polymeric Surfaces.

Herein we describe the preparation of hybrid polymer-inorganic interfaces by the immobilization of polyoxometalate nanoclusters on functionalized polymer surfaces. The polymeric surfaces were made of polystyrene--poly(acrylic acid)/polystyrene (PS--PAA/PS) blends by spin coating on a silicon wafer. The functionalization of the polymer film was obtained by interfacial migration of the amphiphilic block copolymer toward the interface upon water vapor annealing.

Thermally-Triggered Crystal Dynamics and Permanent Porosity in the First Heptatungstate-Metalorganic Three-Dimensional Hybrid Framework.

The hybrid compound [{Cu(cyclam)} (W O )]⋅15.5 H O (1) (cyclam=1,4,8,11-tetraaza-cyclotetradecane) was synthesized by reacting the {Cu(cyclam)} complex with a tungstate source in water at pH 8. Compound 1 exhibits an unprecedented three-dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF-like framework that displays water-filled channels.

A Robust Open Framework Formed by Decavanadate Clusters and Copper(II) Complexes of Macrocyclic Polyamines: Permanent Microporosity and Catalytic Oxidation of Cycloalkanes.

The first decavanadate-based microporous hybrid, namely, [Cu(cyclam)][{Cu(cyclam)}2(V10O28)]·10H2O (1, cyclam = 1,4,8,11-tetraazacyclotetradecane) was prepared by reaction of (VO3)(-) anions and {Cu(cyclam)}(2+) complexes in NaCl (aq) at pH 4.6-4.7 and characterized by elemental analyses, thermogravimetry, and X-ray diffraction (powder, single-crystal) techniques.

New Perspectives for Old Clusters: Anderson-Evans Anions as Building Blocks of Large Polyoxometalate Frameworks in a Series of Heterometallic 3 d-4 f Species.

A series of nine [Sb7W36O133Ln3M2(OAc)(H2O)8](17-) heterometallic anions (Ln3M2; Ln=La-Gd, M=Co; Ln=Ce, M=Ni and Zn) have been obtained by reacting 3 d metal disubstituted Krebs-type tungstoantimonates(III) with early lanthanides. Their unique tetrameric structure contains a novel {MW9O33} capping unit formed by a planar {MW6O24} fragment to which three {WO2} groups are condensed to form a tungstate skeleton identical to that of a hypothetical trilacunary derivative of the ɛ-Keggin cluster. It is shown, for the first time, that classical Anderson-Evans {MW6O24} anions can act as building blocks to construct purely inorganic large frameworks.

The crystal structure of a new polymorph of hexa-aqua-nickel(II) bis-(6-oxo-1,6-di-hydro-pyridine-3-carboxyl-ate).

In a new polymorph of the title salt, [Ni(H2O)6](C6H4NO3)2, the metal atom of the cationic complex lies on a symmetry centre and is coordinated by six water mol-ecules to provide a quite regular octa-hedral coordination environment. These cations inter-act with 6-oxo-1,6-di-hydro-pyridine-3-carboxyl-ate anions through electrostatic inter-actions and by means of O-H⋯O and N-H⋯O hydrogen bonds involving the carboxyl-ate, keto and protonated imine groups of the anion, and the coordinating water mol-ecules from the cationic complex entity to generate a supra-molecular three-dimensional architecture. The previously reported polymorph of this compound presents a network of hydrogen bonds, in which the organic anions establish mutual hydrogen-bonding inter-actions involving their keto and protonated imine groups.

Crystal structure of trans-di-aqua-bis-(1H-pyrazole-3-carboxyl-ato-κ(2) N,O)copper(II) dihydrate.

In the title compound, [Cu(C4H3N2O2)2(H2O)2]·2H2O, the Cu(II) ion is located on an inversion centre and exhibits an axially elongated octa-hedral coordination geometry. The equatorial plane is formed by two N,O-bidentate 1H-pyrazole-3-carboxyl-ate ligands in a trans configuration. The axial positions are occupied by two water mol-ecules.

Crown-shaped tungstogermanates as solvent-controlled dual systems in the formation of vesicle-like assemblies.

Reaction of early lanthanides, GeO2 , and Na2 WO4 in a NaOAc buffer results in large crown-shaped polyoxometalates based on [Ln2 GeW10 O38 ](6-) subunits. By using Ni(2+) as a crystallizing agent, [Na⊂Ln12 Ge6 W60 O228 (H2 O)24 ](35-) (Na⊂Ln12 ) hexamers formed by alternating β(1,5)/β(1,8) subunits were obtained for Ln=Pr, Nd. The addition of K(+) led to a similar anion for Ln=Sm, namely, [K⊂Sm12 Ge6 W60 O228 (H2 O)22 ](35-) (K⊂Sm12 ) and [K⊂K7 Ln24 Ge12 W120 O444 (OH)12 (H2 O)64 ](52-) (K⊂Ln24 ) dodecamers that consist of a central core identical to K⊂Sm12 decorated with six external γ(3,4) subunits for Ln=Pr, Nd.

Rearrangement of a Krebs-type polyoxometalate upon coordination of N,O-bis(bidentate) ligands.

Selective coordination of 2,3-pyzdc to the Krebs-type [{Ni(H2O)3}2(WO2)2(SbW9O33)2](10-) anion promotes a skeletal rearrangement that results in the [(2,3-pyzdc)2{NaNi2(H2O)4Sb2W20O70}2](22-) (Ni4) hybrid dimer showing a novel dinickel containing a 20-tungsto-2-antimonate(III) framework stabilized by N,O-bis(bidentate) bridging ligands. The solution stability and magnetism of Ni4 is discussed.