Publications by authors named "Anne Dolbecq"

75 Publications

Structure-directing role of immobilized polyoxometalates in the synthesis of porphyrinic Zr-based metal-organic frameworks.

Chem Commun (Camb) 2020 Sep;56(70):10143-10146

Université Paris-Saclay, UVSQ, CNRS, UMR 8180, Institut Lavoisier de Versailles, 78035 Versailles Cedex, France.

We evidence the structure-directing role of the PW12O403- polyoxometalate in porphyrinic MOF synthesis whereby it promotes the formation of the kinetic topology. Its immobilization into the MOF is successfully achieved at a high temperature yielding the kinetic MOF-525/PCN-224 phases, while prohibiting the formation of the thermodynamic MOF-545 product. A combined experimental/theoretical approach uses differential PDF and DFT calculations along with solid-state NMR to show the structural integrity of the POM and its location next to the Zr-based nodes.
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http://dx.doi.org/10.1039/d0cc04283hDOI Listing
September 2020

Co-immobilization of a Rh Catalyst and a Keggin Polyoxometalate in the UiO-67 Zr-Based Metal-Organic Framework: In Depth Structural Characterization and Photocatalytic Properties for CO Reduction.

J Am Chem Soc 2020 May 7;142(20):9428-9438. Epub 2020 May 7.

Laboratoire de Chimie des Processus Biologiques, UMR CNRS 8229, Collège de France, Sorbonne Université, PSL Research University, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.

The Keggin-type polyoxometalate (POM) PWO and the catalytic complex Cp*Rh(bpydc)Cl (bpydc = 2,2'-bipyridine-5,5'-dicarboxylic acid) were coimmobilized in the Zr(IV) based metal organic framework UiO-67. The POM is encapsulated within the cavities of the MOF by synthesis, and then, the Rh catalytic complex is introduced by postsynthetic linker exchange. Infrared and Raman spectroscopies, P and C MAS NMR, N adsorption isotherms, and X-ray diffraction indicate the structural integrity of all components (POM, Rh-complex and MOF) within the composite of interest (PW,Cp*Rh)@UiO-67. DFT calculations identified two possible locations of the POM in the octahedral cavities of the MOF: one at the center of a UiO-67 pore with the Cp*Rh complex pointing toward an empty pore and one off-centered with the Cp*Rh pointing toward the POM. P-H heteronuclear (HETCOR) experiments ascertained the two environments of the POM, equally distributed, with the POM in interaction either with the Cp* fragment or with the organic linker. In addition, Pair Distribution Function (PDF) data were collected on the POM@MOF composite and provided key evidence of the structural integrity of the POM once immobilized into the MOF. The photocatalytic activity of the (PW,Cp*Rh)@UiO-67 composite for CO reduction into formate and hydrogen were evaluated. The formate production was doubled when compared with that observed with the POM-free Cp*Rh@UiO-67 catalyst and reached TONs as high as 175 when prepared as thin films, showing the beneficial influence of the POM. Finally, the stability of the composite was assessed by means of recyclability tests. The combination of XRD, IR, ICP, and PDF experiments was essential in confirming the integrity of the POM, the catalyst, and the MOF after catalysis.
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http://dx.doi.org/10.1021/jacs.0c02425DOI Listing
May 2020

Thin Films of Fully Noble Metal-Free POM@MOF for Photocatalytic Water Oxidation.

ACS Appl Mater Interfaces 2019 Dec 12;11(51):47837-47845. Epub 2019 Dec 12.

Laboratoire de Chimie des Processus Biologiques, Collège de France , Sorbonne Université, CNRS UMR 8229, PSL Research University , 11 Place Marcelin Berthelot , 75231 Paris Cedex 05, France.

, which contains the sandwich-type polyoxometalate (POM) [(PWO)Co(HO)] () immobilized in the porphyrinic metal-organic framework (MOF), MOF-545, is a "three-in-one" (porosity + light capture + catalysis) heterogeneous photosystem for the oxygen-evolution reaction (OER). Thin films of this composite were synthesized on transparent and conductive indium tin oxide (ITO) supports using electrophoretic (EP) or drop-casting (DC) methods, thus providing easy-to-use devices. Their electro- and photocatalytic activities for OER were investigated. Remarkably, both types of films exhibit higher turnover numbers (TONs) than the original bulk material previously studied as a suspension for the photocatalytic OER, with TONs after 2 h equal to 1600 and 403 for DC and EP films, respectively, compared to 70 for the suspension. This difference of catalytic activities is related to the proportion of efficiently illuminated crystallites, whereby a DC thin film offers the largest proportion of POM@MOF crystallites exposed to light due to its lower thickness when compared to an EP film or crystals in suspension. Such devices can be easily recycled by simply removing them from the reaction medium and washing them before reuse. The films were fully characterized with extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies, Raman, scanning electron microscopy, and electrochemistry before and after catalysis. The combination of all of these techniques shows the stability of both the POM and the MOF within the composite upon water-oxidation reaction.
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http://dx.doi.org/10.1021/acsami.9b13121DOI Listing
December 2019

Photoactive Polyoxometalate/DASA Covalent Hybrids for Photopolymerization in the Visible Range.

Chemistry 2019 Nov 9;25(63):14349-14357. Epub 2019 Oct 9.

Institut Lavoisier de Versailles, UMR 8180, Université Paris-Saclay, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035, Versailles cedex, France.

The synthesis of TBA-DASA-POM-DASA, the first photoactive covalent hybrid polyoxometalate (POM) incorporating a donor-acceptor Stenhouse adduct (DASA) reverse photochrome, is presented. It has been evidenced that in solution the equilibrium between the colorless cyclopentenone and the highly colored triene conformers is strongly dependent not only on the nature of the solvent but also the countercations, allowing to tune its optical properties. This complex has been further associated to photochromic spironaphtoxazine cations, resulting in a material which can be activated by two distinct optical stimuli. Moreover, when combined with N-methyldiethanolamine, TBA-DASA-POM-DASA constitutes a performing photoinitiating system for polyethylene glycol diacrylate polymerization and under visible light irradiation, a promising result in a domain scarcely developed in POM chemistry.
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http://dx.doi.org/10.1002/chem.201902573DOI Listing
November 2019

An unprecedented {NiSiW} hybrid polyoxometalate with high photocatalytic hydrogen evolution activity.

Chem Commun (Camb) 2019 Apr;55(29):4166-4169

Institut Lavoisier de Versailles, UMR CNRS 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay, 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.

A unique polyoxometalate complex made up of a tetradecanuclear nickel bisphosphonate cluster capping a {SiW9} unit has been characterized. This stable compound exhibits a high hydrogen evolution reaction photocatalytic activity under visible light irradiation via a reductive quenching mechanism.
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http://dx.doi.org/10.1039/c9cc01269aDOI Listing
April 2019

A Multifunctional Dual-Luminescent Polyoxometalate@Metal-Organic Framework EuW@UiO-67 Composite as Chemical Probe and Temperature Sensor.

Front Chem 2018 24;6:425. Epub 2018 Sep 24.

Institut des Matériaux Jean Rouxel, CNRS, Université de Nantes, Nantes, France.

The luminescent [EuWO] polyoxometalate has been introduced into the cavities of the highly porous zirconium luminescent metal-organic framework UiO-67 via a direct synthesis approach, affording the EuW@UiO-67 hybrid. Using a combination of techniques (TGA, BET, elemental analysis, EDX mapping,…) this new material has been fully characterized, evidencing that it contains only 0.25% in europium and that the polyoxometalate units are located inside the octahedral cavities and not at the surface of the UiO-67 crystallites. Despite the low amount of europium, it is shown that EuW@UiO-67 acts as a solid-state luminescent sensor for the detection of amino-acids, the growth of the emission intensity globally following the growth of the amino-acid pKa. In addition, EuW@UiO-67 acts as a sensor for the detection of metallic cations, with a high sensitivity for Fe. Noticeably, the recyclability of the reported material has been established. Finally, it is shown that the dual-luminescent EuW@UiO-67 material behave as a self-calibrated-ratiometric thermometer in the physiological range.
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http://dx.doi.org/10.3389/fchem.2018.00425DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6165868PMC
September 2018

Bicapped Keggin polyoxomolybdates: discrete species and experimental and theoretical investigations on the electronic delocalization in a chain compound.

Dalton Trans 2018 Aug 24;47(31):10636-10645. Epub 2018 May 24.

Institut Lavoisier de Versailles, UMR CNRS 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay, 45 Avenue des Etats-Unis, Versailles 78035 Cedex, France.

Three monomeric polyoxometalates [M(CHN)][α-PMoMoOZn(CHN)]·2HO (M-PMoZn, M = Fe, Co, Ru) with {Zn(bpy)} units capped on reduced α-Keggin polyanions and [M(bpy)] counter-ions were synthesized under hydrothermal conditions. The 1D polymer [N(CH)][Ru(CHN)][α-PMoMoO] (Ru-PMo) was prepared by a similar strategy, in the absence of 2,2'-bpy ligands. In this chain capped reduced Keggin anions are linked via Mo-O-Mo bridges and are surrounded by both tetrabutylammonium cations and [Ru(bpy)] counter-ions. The compounds were characterized in the solid state by single crystal and powder X-ray diffraction and IR spectroscopy and in solution by P NMR spectroscopy. P diffusion ordered NMR spectroscopy (DOSY) indicates that the diffusion coefficient of the dissolved species of Ru-PMo corresponds to a dimeric structure. Magnetic susceptibility measurements performed on Ru-PMo show the existence of antiferromagnetic interactions between the d electrons of the six Mo centers, with a singlet spin ground state. However, attempts to fit the data in the 2-300 K temperature range with Heisenberg Hamiltonians adapted for 0 or 1D systems suggest that these electrons are delocalized. Density Functional Theory (DFT) and Wave Function Theory (WFT) calculations indicate a migration of the electrons of the capping Mo centers into the PMo units at high temperature, allowing the rationalization of the experimental observations.
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http://dx.doi.org/10.1039/c8dt01313fDOI Listing
August 2018

Anderson-Type Polyoxometalates Functionalized by Tetrathiafulvalene Groups: Synthesis, Electrochemical Studies, and NLO Properties.

Inorg Chem 2018 Apr 22;57(7):3742-3752. Epub 2018 Mar 22.

Institut Lavoisier de Versailles , UMR 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay , 45 Avenue des Etats-Unis , CEDEX 78035 Versailles , France.

Three polyoxometalates (POMs) functionalized by tetrathiafulvalene (TTF) molecules have been synthesized by a coupling reaction between the Anderson-type POMs [MnMoO{(OCH)CNH}] or [AlMoO(OH){(OCH)CNH}] and the TTF carboxylic acid derivative (MeS)TTF(S-CH-COH). The monofunctionalized TTF-AlMo POM contains one TTF group covalently grafted on an Al Anderson platform. The symmetrical TTF-MnMo-TTF POM possesses two TTF groups grafted on each side of a Mn Anderson derivative while the asymmetrical TTF-MnMo-SP POM contains a TTF and a spiropyran groups. These three trianionic species have been characterized by elemental analysis, H and C NMR, FT-IR spectroscopy, ESI-MS spectrometry, and single-crystal X-ray diffraction (for TTF-MnMo-TTF). In the solid state, the grafted TTF molecules of TTF-MnMo-TTF POMs interact via S···S and π···π interactions and form chains. The electrochemical properties of the complexes reflect the contributions of both the inorganic POM and the TTF moieties. Despite adsorption of the oxidized hybrid species on the Pt grid working electrode, UV-vis-NIR spectroelectrochemical investigations evidence peaks characteristic of the oxidation of the TTF units. Finally, hyper-Rayleigh scattering (HRS) measurements show that the three novel TTF derivatives exhibit β values between 20 and 37 × 10 esu. Moreover it is observed that the oxidation of the TTF moieties by Fe ions increases the NLO response. These values are in the order of magnitude of that found for the well-known 4-dimethylamino- N-methyl-4-stilbazolium (DAS) cation (β = 60 × 10 esu).
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http://dx.doi.org/10.1021/acs.inorgchem.7b02976DOI Listing
April 2018

A Fully Noble Metal-Free Photosystem Based on Cobalt-Polyoxometalates Immobilized in a Porphyrinic Metal-Organic Framework for Water Oxidation.

J Am Chem Soc 2018 03 2;140(10):3613-3618. Epub 2018 Feb 2.

Institut Lavoisier de Versailles, UMR CNRS 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay , 45 Avenue des Etats-Unis , Versailles 78035 Cedex , France.

The sandwich-type polyoxometalate (POM) [(PWO)Co(HO)] was immobilized in the hexagonal channels of the Zr(IV) porphyrinic MOF-545 hybrid framework. The resulting composite was fully characterized by a panel of physicochemical techniques. Calculations allowed identifying the localization of the POM in the vicinity of the Zr clusters and porphyrin linkers constituting the MOF. The material exhibits a high photocatalytic activity and good stability for visible-light-driven water oxidation. It thus represents a rare example of an all-in-one fully noble metal-free supramolecular heterogeneous photocatalytic system, with the catalyst and the photosensitizer within the same porous solid material.
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http://dx.doi.org/10.1021/jacs.7b11788DOI Listing
March 2018

Simple and efficient polyoxomolybdate-mediated synthesis of novel graphene and metal nanohybrids for versatile applications.

J Colloid Interface Sci 2018 Mar 23;514:507-516. Epub 2017 Dec 23.

Laboratoire de Chimie-Physique, UMR 8000 CNRS, Université Paris-Sud, Orsay F-91405, France.

The application of nanohybrids based on polyoxomolybdates, reduced graphene oxide (rGO) and/or metal nanoparticles (NPs) high-performance electrode materials in electrocatalysis and energy storage devices is promising but still limited due to the complexity and the cost of the synthesis. Here we introduce a simple polyoxomolybdate, [MoO(OH)(HO)(CO)] (MoS), as reducing and stabilizing agent for the facile and one-pot syntheses of large quantity of highly stable MoS/rGO and MoS/Au NPs nanohybrids in aqueous solution without any catalyst or toxic co-solvent. They were characterized by various physical techniques and electrochemistry which confirm strong interaction between MoS and rGO sheets. We also used DFT calculations to investigate the affinity between MoS or its neutral form with graphene. The adsorption energy for the most stable configuration is -1.97 eV, indicating a strong adsorption process of MoS, which can also be confirmed by the distance (3.04 Å) and the charge transfer (0.86 e) between MoS and graphene. These observations are also consistent with the electrochemical results which underscore the excellent redox properties and high stability of MoS/rGO. Importantly, the MoS/rGO nanohybrids are excellent noble metal-free electrocatalysts for hydrogen peroxide reduction with high sensitivity, large detection range and low detection limit. Finally, the preliminary tests reveal that the electrode materials based on MoS/rGO and a low-cost carbon cloth (CC) composite MoS/rGO/CC may have a potential for an application in energy storage as performant and flexible supercapacitor, showing specific capacitance as high as 870 F g at 10 mV s and excellent stability after 5000 cycles.
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http://dx.doi.org/10.1016/j.jcis.2017.12.039DOI Listing
March 2018

High Oxygen Reduction Reaction Performances of Cathode Materials Combining Polyoxometalates, Coordination Complexes, and Carboneous Supports.

ACS Appl Mater Interfaces 2017 Nov 27;9(44):38486-38498. Epub 2017 Oct 27.

Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences , 100190 Beijing, China.

A series of carbonaceous-supported precious-metal-free polyoxometalate (POM)-based composites which can be easily synthesized on a large scale was shown to act as efficient cathode materials for the oxygen reduction reaction (ORR) in neutral or basic media via a four-electron mechanism with high durability. Moreover, exploiting the versatility of the considered system, its activity was optimized by the judicious choice of the 3d metals incorporated in the {(PW)M} (M = Co, Ni) POM core, the POM counterions and the support (thermalized triazine-based frameworks (TTFs), fluorine-doped TTF (TTF-F), reduced graphene oxide, or carbon Vulcan XC-72. In particular, for {(PW)Ni}/{Cu(ethylenediamine)}/TTF-F, the overpotential required to drive the ORR compared well with those of Pt/C. This outstanding ORR electrocatalytic activity is linked with two synergistic effects due to the binary combination of the Cu and Ni centers and the strong interaction between the POM molecules and the porous and highly conducting TTF-F framework. To our knowledge, {(PW)Ni}/{Cu(ethylenediamine)}/TTF-F represents the first example of POM-based noble-metal-free ORR electrocatalyst possessing both comparable ORR electrocatalytic activity and much higher stability than that of Pt/C in neutral medium.
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http://dx.doi.org/10.1021/acsami.7b10989DOI Listing
November 2017

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

Inorg Chem 2017 Jul 20;56(13):7558-7565. Epub 2017 Jun 20.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay , 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.

We synthesized a series of polyoxometalate-bisphosphonate complexes containing MoO octahedra, zoledronate, or an N-alkyl (n-C or n-C) zoledronate analogue, and in two cases, Mn as a heterometal. MoL (L = Zol, ZolC, ZolC) and MoLMn (L = Zol, ZolC) were characterized by using single-crystal X-ray crystallography and/or IR spectroscopy, elemental and energy dispersive X-ray analysis and P NMR. We found promising activity against human nonsmall cell lung cancer (NCI-H460) cells with IC values for growth inhibition of ∼5 μM per bisphosphonate ligand. The effects of bisphosphonate complexation on IC decreased with increasing bisphosphonate chain length: C ≈ 6.1×, C ≈ 3.4×, and C ≈ 1.1×. We then determined the activity of one of the most potent compounds in the series, MoZolMn(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.
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http://dx.doi.org/10.1021/acs.inorgchem.7b01114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5535315PMC
July 2017

Photochromism and Dual-Color Fluorescence in a Polyoxometalate-Benzospiropyran Molecular Switch.

Angew Chem Int Ed Engl 2017 04 24;56(17):4872-4876. Epub 2017 Mar 24.

Institut Parisien de Chimie Moléculaire UMR CNRS 8232, Sorbonne Universités, UPMC-Paris06, 4 Place Jussieu, F-, 75005, Paris, France.

The photophysical properties of a Keggin-type polyoxometalate (POM) covalently bounded to a benzospiropyran (BSPR) unit have been investigated. These studies reveal that both closed and open forms are emissive with distinct spectral features (λ (closed form)=530 nm, λ (open form)=670 nm) and that the fluorescence of the BSPR unit of the hybrid is considerably enhanced compared to BSPR parent compounds. While the fluorescence excitation energy of the BSPR reference compounds (370 nm) is close to the intense absorption responsible of the photochromic character (350 nm), the fluorescence excitation of the hybrid is shifted to lower energy (400 nm), improving the population of the emissive state. Combined NOESY NMR and theoretical calculations of the closed form of the hybrid give an intimate understanding of the conformation adopted by the hybrid and show that the nitroaryl moieties of the BSPR is folded toward the POM, which should affect the electronic properties of the BSPR.
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http://dx.doi.org/10.1002/anie.201701860DOI Listing
April 2017

Light- and Solvent-Controlled Self-Assembly Behavior of Spiropyran-Polyoxometalate-Alkyl Hybrid Molecules.

Chemistry 2016 Aug 12;22(33):11756-62. Epub 2016 Jul 12.

Department of Polymer Science, University of Akron, Akron, Ohio, 44325, USA.

A molecular photochromic spiropyran-polyoxometalate-alkyl organic-inorganic hybrid has been synthesized and fully characterized. The reversible switching of the hydrophobic spiropyran fragment to the hydrophilic merocyanine one can be easily achieved under light irradiation at different wavelengths. This switch changes the amphiphilic feature of the hybrid, leading to a light-controlled self-assembly behavior in solution. It has been shown that the hybrid can reversibly self-assemble into vesicles in polar solvents and irreversibly into reverse vesicles in non-polar solvents. The sizes of the vesicles and the reverse vesicles are both tunable by the polarity of the solvent, with the hydrophobic interactions being the main driving force.
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http://dx.doi.org/10.1002/chem.201601173DOI Listing
August 2016

Single-Molecule Magnet Behavior of Individual Polyoxometalate Molecules Incorporated within Biopolymer or Metal-Organic Framework Matrices.

Chemistry 2016 May 15;22(19):6564-74. Epub 2016 Apr 15.

Institut Lavoisier de Versailles, UMR CNRS 8180, Université Paris Saclay, Université de Versailles St-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035, Versailles cedex, France.

The chemically and structurally highly stable polyoxometalate (POM) single-molecule magnet (SMM) [(FeW9 O34 )2 Fe4 (H2 O)2 ](10-) (Fe6 W18 ) has been incorporated by direct or post-synthetic approaches into a biopolymer gelatin (Gel) matrix and two crystalline metal-organic frameworks (MOFs), including one diamagnetic (UiO-67) and one magnetic (MIL-101(Cr)). Integrity of the POM in the Fe6 W18 @Gel, Fe6 W18 @UiO-67 and Fe6 W18 @MIL-101(Cr) composites was confirmed by a set of complementary techniques. Magnetic studies indicate that the POMs are magnetically well isolated. Remarkably, in Fe6 W18 @Gel, the SMM properties of the embedded molecules are close to those of the crystals, with clear quantum tunneling steps in the hysteresis loops. For the Fe6 W18 @UiO-67 composite, the molecules retain their SMM properties, the energy barrier being slightly reduced in comparison to the crystalline material and the molecules exhibiting a tunneling rate of magnetization significantly faster than for Fe6 W18 @Gel. When Fe6 W18 is introduced into MIL-101(Cr), the width of the hysteresis loops is drastically reduced and the quantum tunneling steps are smeared out because of the magnetic interactions between the antiferromagnetic matrix and the SMM guest molecules.
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http://dx.doi.org/10.1002/chem.201600202DOI Listing
May 2016

Studies of the Effectiveness of Bisphosphonate and Vanadium-Bisphosphonate Compounds In Vitro against Axenic Leishmania tarentolae.

Oxid Med Cell Longev 2016 29;2016:9025627. Epub 2016 Feb 29.

Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA.

Leishmaniasis is a disease that is a significant problem for people, especially in tropical regions of the world. Current drug therapies to treat the disease are expensive, not very effective, and/or of significant side effects. A series of alkyl bisphosphonate compounds and one amino bisphosphonate compound, as well as alendronate and zoledronate, were tested as potential agents against Leishmania tarentolae. Also, two polyoxometalates (POMs) with nitrogen-containing bisphosphonate ligands, vanadium/alendronate (V5(Ale)2) and vanadium/zoledronate (V3(Zol)3), were tested against L. tarentolae and compared to the results of the alendronate and zoledronate ligands alone. Of the compounds evaluated in this study, the V5(Ale)2 and V3(Zol)3 complexes were most effective in inhibiting the growth of L. tarentolae. The V5(Ale)2 complex had a larger impact on cell growth than either alendronate or orthovanadate alone, whereas zoledronate itself has a significant effect on cell growth, which may contribute to the activity of the V3(Zol)3 complex.
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http://dx.doi.org/10.1155/2016/9025627DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4789522PMC
December 2016

Heteroanionic Materials Based on Copper Clusters, Bisphosphonates, and Polyoxometalates: Magnetic Properties and Comparative Electrocatalytic NO(x) Reduction Studies.

Inorg Chem 2016 Feb 4;55(4):1551-61. Epub 2016 Feb 4.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, Université Paris-Saclay , 45 Avenue des Etats-Unis, 78035 Versailles cedex, France.

Three compounds associating for the first time polyoxotungstates, bisphosphonates, and copper ions were structurally characterized. They consist in heteropolyanionic monodimensional materials where [Cu6(Ale)4(H2O)4](4-) (Ale = alendronate = [O3PC(O)(C3H6NH3)PO3](4-)) complexes alternate with polyoxometalate (POM) units. In Na12[{SiW9O34Cu3(Ale)(H2O)}{Cu6(Ale)4(H2O)4}]·50H2O (SiW9CuAle), the polyoxometalate core consists in a {SiW9Cu3} monomer capped by a pentacoordinated Ale ligand, while sandwich-type Keggin {(SbW9O33)2Cu3(H2O)(2.5)Cl(0.5)} and Dawson {(P2W15O56)2Cu4(H2O)2} complexes are found in Na8Li29[{(SbW9O33)2Cu3(H2O)(2.5)Cl(0.5)}2{Cu6(Ale)4(H2O)4}3]·163H2O (SbW9CuAle) and Na20[{(P2W15O56)2Cu4(H2O)2}{Cu6(Ale)4(H2O)4}]·50H2O (P2W15CuAle), respectively. A comparative magnetic study of the SiW9CuAle and SbW9CuAle compounds enabled full quantification of the Cu(II) superexchange interactions both for the POM and non-POM subunits, evidencing that, while the paramagnetic centers are anti-ferromagnetically coupled in the polyoxometalate units, both anti-ferromagnetic and ferromagnetic interactions coexist in the {Cu6(Ale)4(H2O)4} cluster. All the studied compounds present a good efficiency upon the reduction of HNO2 or NO2(-), the POM acting as a catalyst. However, it has been found that SbW9CuAle is inactive toward the reduction of nitrates, highlighting that both the {(SbW9O33)2Cu3} unit and the {Cu6(Ale)4(H2O)4} cluster do not act as electrocatalysts for this reaction. In contrast, SiW9CuAle and P2W15CuAle have shown a significant activity upon the reduction of NO3(-) and thus both at pH 1 and pH 5, evidencing that the chemical nature of the polyoxometalate is a crucial parameter even if it acts as precatalyst. Moreover, comparison of the activities of P2W15CuAle and [(P2W15O56)2Cu4(H2O)2](16-) evidenced that if the [Cu6(Ale)4(H2O)4](4-) cluster does not act as electrocatalyst, it acts as a cofactor, significantly enhancing the catalytic efficiency of the active POM.
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http://dx.doi.org/10.1021/acs.inorgchem.5b02456DOI Listing
February 2016

An all-inorganic polyoxometalate-polyoxocation chemical garden.

Chem Commun (Camb) 2016 Jan;52(9):1911-4

WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK.

Herein, we show it is possible to produce wholly inorganic chemical gardens from a cationic polyoxometalate (POM) seed in an anionic POM solution, demonstrating a wholly POM-based chemical garden system that produces architectures over a wide concentration range. Six concentration dependent growth regimes have been discovered and characterized: clouds, membranes, slugs, tubes, jetting and budding.
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http://dx.doi.org/10.1039/c5cc09536kDOI Listing
January 2016

A high fatigue resistant, photoswitchable fluorescent spiropyran-polyoxometalate-BODIPY single-molecule.

Chem Commun (Camb) 2015 Nov;51(89):16088-91

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin, 45 avenue des Etats-Unis, 78035 Versailles Cedex, France.

The tuning of the fluorescence through the activation of the photochromic part in an unprecedented covalent spiropyran-polyoxometalate-BODIPY tricomponent points out the high photofatigue resistance of such molecular switches.
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http://dx.doi.org/10.1039/c5cc06217aDOI Listing
November 2015

Sequential Synthesis of 3 d-3 d, 3 d-4 d, and 3 d-5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions.

Chemistry 2015 Aug 14;21(34):12153-60. Epub 2015 Jul 14.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex (France).

The Co7 (AlePy)2 polyoxometalate, which encloses a {(PW9 )2 Co(II) 7 } core covalently bound to two free aminopyridine groups through bisphosphonate ligands (AlePy), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc (Co7 (AlePyZn)2 ), cobalt/palladium (Co7 (AlePyPd)2 ), and cobalt/platinum (Co7 (AlePyPt)2 ) species. A composite based on the water-insoluble precious metal-free Co7 (AlePyZn)2 compound and the low-cost carbon material Vulcan XC-72 has been selected as a cathode material (Co7 Zn/C) for oxygen reduction reaction studies. The electrocatalytic performances of the Co7 Zn/C hybrids were assessed at neutral and basic pH, showing that Co7 Zn/C exhibits high selectivity for the four-electron reduction of O2 . Moreover, its durability is superior to that of a commercial Pt/C catalyst with 20 % loading. Also, comparative studies performed in the presence of methanol have indicated that Co7 Zn/C has a much better tolerance to the crossover effect than Pt/C. Altogether, these results indicate for the first time that, even in neutral media, polyoxometalate/carbon composites can represent low-cost oxygen reduction catalysts that can function stably, for a long time, and with high performance.
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http://dx.doi.org/10.1002/chem.201501609DOI Listing
August 2015

Polyoxomolybdate Bisphosphonate Heterometallic Complexes: Synthesis, Structure, and Activity on a Breast Cancer Cell Line.

Chemistry 2015 Jul 15;21(29):10537-47. Epub 2015 Jun 15.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles St-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles cedex (France).

Six polyoxometalates containing Mn(II) , Mn(III) , or Fe(III) as the heteroelement were synthesized in water by treating Mo(VI) precursors with biologically active bisphosphonates (alendronate (Ale), zoledronate (Zol), an n-alkyl bisphosphonate (BPC9 ), an aminoalkyl bisphosphonate (BPC8 NH2 )) in the presence of additional metal ions. The Pt complex was synthesized from a polyoxomolybdate bisphosphonate precursor with Mo(VI) ions linked by the 2-pyridyl analogue of alendronate (AlePy). The complexes Mo4 Ale2 Mn, Mo4 Zol2 Mn, Mo4 Ale2 Fe, Mo4 Zol2 Fe, Mo4 (BPC8 NH2 )2 Fe, and Mo4 (BPC9 )2 Fe contain two dinuclear Mo(VI) cores bound to a central heterometallic ion. The oxidation state of manganese was determined by magnetic measurements. Complexes Mo12 (AlePy)4 and Mo12 (AlePy)4 Pt4 were studied by solid-state NMR spectroscopy and the photochromic properties were investigated in the solid state; both methods confirmed the complexation of Pt. Activity against the human breast adenocarcinoma cell line MCF-7 was determined and the most potent compound was Mn(III) -containing Mo4 Zol2 Mn (IC50 ≈1.3 μM). Unlike results obtained with vanadium-containing polyoxometalate bisphosphonates, cell growth inhibition was rescued by the addition of geranylgeraniol, which reverses the effects of bisphosphonates on isoprenoid biosynthesis/protein prenylation. The results indicate an important role for both the heterometallic element and the bisphosphonate ligand in the mechanism of action of the most active compounds.
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http://dx.doi.org/10.1002/chem.201406565DOI Listing
July 2015

Immobilization of polyoxometalates in the Zr-based metal organic framework UiO-67.

Chem Commun (Camb) 2015 Feb;51(14):2972-5

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles cedex, France.

The encapsulation of polyoxometalates within the large pores of the Zr(iv) biphenyldicarboxylate UiO-67 metal-organic framework has been achieved, for the first time, by direct solvothermal synthesis. The resulting POM@UiO-67 composite materials were fully characterized by XRPD, IR, MAS NMR, N2 porosimetry measurements and cyclic voltammetry.
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http://dx.doi.org/10.1039/c4cc09986aDOI Listing
February 2015

Immobilization of Co-containing polyoxometalates in MIL-101(Cr): structural integrity versus chemical transformation.

Dalton Trans 2014 Sep;43(33):12698-705

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.

The encapsulation of three different cobalt substituted polyoxometalates (POMs) within the mesoporous chromium(iii) terephthalate MIL-101(Cr) metal-organic framework (MOF) was studied by a simple and green impregnation method using water. The POM@MIL composite materials were fully characterized by EDX, XRPD, IR, MAS NMR and N2 porosimetry measurements. The encapsulated POMs were then extracted by an exchange procedure using a LiCl solution. (31)P NMR spectroscopy is the key experiment which indicates that the monosubstituted Keggin anion [PW11CoO39(H2O)](5-) (PW11Co) and the sandwich-type anion [(PW9O34)2Co4(H2O)2](10-) (P2W18Co4) can be encapsulated and extracted without degradation, neither of the POM nor of the MOF, while the hybrid sandwich-type POM [(PW9O34)2Co7(OH)2(H2O)4(O3PC(O)(C3H6NH3)PO3)2](14-) (Co7-Ale) evolves into P2W18Co4 inside the cavities of the mesoporous material. The PW11Co Keggin anion is the most quantitatively uploaded and the most easily extracted anion. (31)P MAS-NMR spectroscopy further suggests that this anion is more mobile inside the cavities of the MOF than the P2W18Co4 POM.
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http://dx.doi.org/10.1039/c4dt01286kDOI Listing
September 2014

Photochromic properties of polyoxotungstates with grafted spiropyran molecules.

Inorg Chem 2013 Oct 19;52(19):11156-63. Epub 2013 Sep 19.

Institut Parisien de Chimie Moléculaire, IPCM, UMR CNRS 7201, Université Pierre et Marie Curie, UPMC Univ Paris 06, 4 Place Jussieu, Case 42, F-75005 Paris, France.

The first systems associating in a single molecule polyoxotungstates (POTs) and photochromic organic groups have been elaborated. Using the (TBA)4[PW11O39{Sn(C6H4I)}] precursor, two hybrid organic-inorganic species where a spiropyran derivative (SP) has been covalently grafted onto a {PW11Sn} fragment via a Sonogashira coupling have been successfully obtained. Alternatively, a complex containing a silicotungstate {PW11Si2} unit connected to two spiropyran entities has been characterized. The purity of these species has been assessed using several techniques, including (1)H and (31)P NMR spectroscopy, mass spectrometry, and electrochemical measurements. The optical properties of the hybrid materials have been investigated both in solution and in the solid state. These studies reveal that the grafting of SPs onto POTs does not significantly alter the photochromic behavior of the organic chromophore in solution. In contrast, these novel hybrid SP-POT materials display highly effective solid-state photochromism from neutral SP molecules initially nonphotochromic in the crystalline state. The photoresponses of the SP-POT systems in the solid state strongly depend on the nature and the number of grafted SP groups.
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http://dx.doi.org/10.1021/ic401380aDOI Listing
October 2013

Properties of a tunable multinuclear nickel polyoxotungstate platform.

Chemistry 2013 May 27;19(21):6753-65. Epub 2013 Mar 27.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.

A series of hybrid nickel bisphosphonate (BP) polyoxometalates (POMs) has been isolated. The complexes NaK-Ni7-Ale2 (Ale = [H2O3PC(C3H6NH2)(OH)PO3H2]) and NaNH4-Ni7-Ale2 are both made of two {PW9O34} fragments enclosing a heptanuclear Ni(II) core connected to two alendronate ligands. By pre-functionalising the alendronate moiety through the amino group, the naphthalene (napht) derivative Ni7-(AleNapht)2 and the compounds Ni7-(AlePy2 Ni)2 (py = pyridyl) and Ni7-(AleAc2Ni)2 (Ac = acyl) have been obtained. Compared with the NaK-Ni7-Ale2 species, these last two complexes contain two additional Ni(II) centres connected through two bis(2-pyridylmethyl)amine or two iminodiacetate groups, respectively. This results show that it is possible to functionalise the heptanuclear POM in a controlled manner. Quantification of the magnetic interactions in NaK-Ni7-Ale2 revealed that in the {Ni7} core, ferromagnetic interactions are predominant, with a S = 5 ground state. Magnetisation versus dc field sweeps on a single crystal of NaK-Ni7-Ale2 exhibited hysteresis at low temperature. (1)H and (31)P NMR studies in aqueous solution performed on NaK-Ni7-Ale2 and Ni7-(AleNapht)2 evidenced that the PW9/Ni7/bisphosphonate assembly is stable in solution. This was completed by (31)P magic angle spinning (MAS) investigations and confirmed by (1)H DOSY experiments. The electrochemistry of these compounds proceeds through two well-defined four-electron chemically reversible waves in a medium at pH 6. NaK-Ni7-Ale2 proved to be efficient for the electrocatalytic reduction of nitrate, nitrite and nitrous oxide. Remarkably, its electrocatalytic efficiency for nitrate reduction is approximately three times higher than those previously reported for POMs in a medium at pH >4 under the same potential. The catalytic properties of two representatives of the hybrid family were also examined. It is shown that these nickel bisphosphonate polyoxotungstates are pre-catalysts for the oxidation of alcohols into ketones or carboxylic acids, depending on the classes of alcohols considered, the stoichiometric oxidant used being H2O2. Noticeably, it has been found that an analogous cobalt bisphosphonate polyoxotungstate complex does not present any related activity, highlighting the crucial role of the 3d cations on the catalytic process.
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http://dx.doi.org/10.1002/chem.201204366DOI Listing
May 2013

Sulfonium polyoxometalates: a new class of solid-state photochromic hybrid organic-inorganic materials.

Inorg Chem 2013 Jan 8;52(2):555-7. Epub 2013 Jan 8.

Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes cedex, France.

For the very first time, sulfonium polyoxometalate (POM) assemblies are shown to develop efficient solid-state photochromism in ambient conditions. The optical properties of the already known Rb(0.75)(NH(4))(5.25)[(Mo(3)O(8))(2)O(O(3)PC(CH(2)S(CH(3))(2))OPO(3))(2)]·8H(2)O (1) and a new material (Me(3)S)(4)[Mo(8)O(26)] (2) under UV excitation are investigated by diffuse reflectance spectroscopy, revealing that the color change effect is highly tunable playing with the nature of the POM. A mechanism involving the photoreduction of Mo(6+) cations associated with electron transfers from the sulfonium cations toward the POMs is proposed.
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http://dx.doi.org/10.1021/ic302477pDOI Listing
January 2013

Photo- and electrochromic properties of covalently connected symmetrical and unsymmetrical spiropyran-polyoxometalate dyads.

Chem Commun (Camb) 2012 Dec;48(99):12103-5

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin, 45 avenue des Etats-Unis, 78035 Versailles Cedex, France.

Polyoxometalates covalently linked to one or two spiropyran entities have been isolated. These organic-inorganic hybrids exhibit multi-electrochromic and photochromic properties.
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http://dx.doi.org/10.1039/c2cc35376hDOI Listing
December 2012

Diversity in structures and properties of 3d-incorporating polyoxotungstates.

Chem Soc Rev 2012 Nov 13;41(22):7497-536. Epub 2012 Aug 13.

Institut Lavoisier de Versailles, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, UMR 8180, 78035 Versailles cedex, France.

This critical review surveys the 3d substituted magnetic polyoxotungstate (POT) molecular compounds reported these last ten years, illustrating the huge variety of topologies that these systems can adopt. Both purely inorganic and organic/inorganic species have been considered, and the cited compounds have been classified according to their nuclearity, i.e., the number of magnetic 3d centres embedded in the POT matrix, which can be as high as 48. This review highlights the synthetic conditions, the solubility and the stability in solution of these species. The magnetic, catalytic and electrocatalytic properties of these complexes are also summarized.
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http://dx.doi.org/10.1039/c2cs35148jDOI Listing
November 2012

ε-Keggin-based coordination networks: Synthesis, structure and application toward green synthesis of polyoxometalate@graphene hybrids.

Dalton Trans 2012 Sep 18;41(33):9989-99. Epub 2012 Jul 18.

Group of Materials Developed by Design, Division of Chemistry and Technology of Materials, Institute of Materials Research and Engineering, University of Havana, Havana, 10400, Cuba.

Four coordination networks based on the {ε-PMo(V)(8)Mo(VI)(4)O(40)(OH)(4)Zn(4)} Keggin unit (εZn) have been synthesized under hydrothermal conditions. (TBA)(3){PMo(V)(8)Mo(VI)(4)O(36)(OH)(4)Zn(4)}[C(6)H(4)(COO)(2)](2) (ε(isop)(2)) is a 2D material with monomeric εZn units connected via 1,3 benzenedicarboxylate (isop) linkers and tetrabutylammonium (TBA) counter-cations lying between the planes. In (TPA)(3){PMo(V)(8)Mo(VI)(4)O(37)(OH)(3)Zn(4)}[C(6)H(3)(COO)(3)] (TPA[ε(trim)](∞)), 1D inorganic chains formed by the connection of εZn POMs, via Zn-O bonds, are linked via 1,3,5 benzenetricarboxylate (trim) ligands into a 2D compound with tetrapropylammonium (TPA) cations as counter-cations. (TBA){PMo(V)(8)Mo(VI)(4)O(40)Zn(4)}(C(7)H(4)N(2))(2)(C(7)H(5)N(2))(2)·12H(2)O (ε(bim)(4)) is a molecular material with monomeric εZn POMs bound to terminal benzimidazole (bim) ligands. Finally, (TBA)(C(10)H(10)N(4))(2)(HPO(3)){PMo(V)(8)Mo(VI)(4)O(40)Zn(4)}(2)(C(10)H(9)N(4))(3)(C(10)H(8)N(4)) (ε(2)(pazo)(4)) is a 1D compound with dimeric (εZn)(2) POMs connected by HPO(3)(2-) ions and terminal para-azobipyridine (pazo) ligands. In this compound an unusual bond cleavage of the central N[double bond, length as m-dash]N bond of the pazo ligand is observed. We report also a green chemistry-type one-step synthesis method carried out in water at room temperature using ε(2)(pazo)(4) and ε(isop)(2) as reducing agent of graphite oxide (GO) to obtain graphene (G). The POM@G hybrids were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, powder X-ray diffraction, energy dispersive X-ray analysis, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and cyclic voltammetry.
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http://dx.doi.org/10.1039/c2dt30537bDOI Listing
September 2012

Functionalized polyoxometalates with covalently linked bisphosphonate, N-donor or carboxylate ligands: from electrocatalytic to optical properties.

Chem Commun (Camb) 2012 Aug 5;48(67):8299-316. Epub 2012 Jul 5.

Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles cedex, France.

The structures of two families of hybrid organic-inorganic polyoxometalates (POMs) functionalized by covalently grafted carboxylate or bisphosphonate ligands are overviewed. The first family concerns the so-called POMOF materials, built from the connection of mixed-valent ε-Keggin type polyoxomolybdates via N-donor or carboxylate organic molecules coordinated to transition metal ions (Zn(II), Co(II), Ni(II)) grafted at the surface of the POMs. The simulation of the hypothetical zeolitic-like POMOF structures is presented and compared to the experimental ones. The second family gathers the various molecular Mo(V), Mo(VI) and W(VI) POMs incorporating directly into their architecture bisphosphonate (BP) ligands. The potentiality of this family of hybrid POMs comes from the organic group grafted on the carbon atom which bears the two phosphonate groups. For both families, besides the structural description, synthetic trends and an overview of their properties are presented. Namely, the electrocatalytic properties (production of H(2) and reduction of BrO(3)(-)) of the ε-Keggin type polyoxomolybdates are described. The optical and biological activities of the POM-BP compounds as well as their ability to form nanosystems are also reported.
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http://dx.doi.org/10.1039/c2cc31667fDOI Listing
August 2012