Anna Proust

Pierre and Marie Curie University - Paris 6, Lutetia Parisorum, Île-de-France, France

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Publications (127)464.14 Total impact

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    ABSTRACT: We demonstrate the success in self-assembling pyrene-modified Dawson–Wells-type polyoxometalates (POMs) with single walled carbon nanotubes (SWCNTs) by means of π–π interactions. In this context, the immobilization of POMs onto SWCNTs is corroborated by aberration-corrected high-resolution electron microscopy, thermogravimetric analysis, and Raman spectroscopy. From steady-state and time-resolved photophysical techniques we derived evidence for mutual interactions between SWCNTs and POMs in the excited states. The latter are the inception to a charge transfer from the SWCNTs to the POMs. Our results corroborate the suitability of POM–SWCNTs assemblies for photoactive molecular devices.
    Chemical Science 07/2014; · 8.31 Impact Factor
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    ABSTRACT: A new polyoxomolybdate-based hybrid platform TBA4[PMo11O39{Sn(p-C6H4I)}] is reported. The presence of a post-functionalisable iodo-aryl moiety allows the grafting of a ferrocenyl moiety onto the POM. The electrochemical characterisation shows the effect of molybdenum on the electron reservoir properties of POM-based hybrids, which are further enhanced upon the addition of an acid.
    Chemical communications (Cambridge, England). 06/2014;
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    ABSTRACT: Covalent amphiphilic polyoxometalates generated from alkylphosphonic acids have been synthesized, characterized and monitored by multinuclear NMR spectroscopy. Among them, K3H[γ-SiW10O36(C12H25PO)2] has been successfully used as a surfactant for the stabilization of a Winsor I type microemulsion system.
    Chemical Communications 05/2014; · 6.38 Impact Factor
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    ABSTRACT: Spontaneously adsorbed monolayers have been formed on gold electrodes using a Keggin polyoxotungstate, with covalently attached alkanethiol linkers of two different lengths. Films of both polyoxotungstates show two well defined reduction processes associated with the polyoxotungstate centers where the ionic liquid, [BMIM][BF4], acts as supporting electrolyte. The surface coverages are both less than that expected for a close packed monolayer. For the short and long linkers, the voltammetric response can be described in terms of the Butler-Volmer response involving a surface confined species using standard heterogeneous electron transfer rate constants of 170 s-1 and 140 s-1 for the first reduction and 150 s-1 and 100 s-1 for the second reduction processes, respectively. Significantly, the rate of electron transfer to a solution phase redox probe, ferrocyanide, is significantly more sensitive to the length of the linker than the rate of electron transfer to the tungstate centers. This behavior probably arises due to potential induced changes in the film structure.
    Langmuir 03/2014; · 4.38 Impact Factor
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    ABSTRACT: A Keggin-type POM is attached to gold or glassy carbon surfaces by electro(chemical) or peptidic coupling. In addition to demonstrating the robust attachment of the POMs (by electrochemistry, XPS and IRRAS), the surface concentration, layer thickness and rate constant for electron transfer from the surface to the POMs have been measured. The use of such complementary techniques is mandatory to properly characterize the modified electrodes. Whatever the grafting method, experimental conditions are found to allow monolayer or submonolayer coverage. Besides covalently grafted species, additional electrostatic bonded POMs are present in the film. Cathodic polarization allows removing them to get a grafted film that is stable with time and potential, which is a requisite toward the design of molecular memories.
    Langmuir 02/2014; · 4.38 Impact Factor
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    ABSTRACT: 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.
    Inorganic Chemistry 09/2013; · 4.59 Impact Factor
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    ABSTRACT: Polyoxometalates (POMs) are attractive candidates for the rational design of multi-level charge-storage materials because they display reversible multi-step reduction processes in a narrow range of potentials. The functionalization of POMs allows for their integration in hybrid complementary metal oxide semiconductor (CMOS)/molecular devices, provided that fine control of their immobilisation on various substrates can be achieved. Owing to the wide applicability of the diazonium route to surface modification, a functionalized Keggin-type POM [PW11 O39 {Ge(p-C6 H4 -CC-C6 H4 -${{\rm N}{{+\hfill \atop 2\hfill}}}$)}](3-) bearing a pending diazonium group was prepared and subsequently covalently anchored onto a glassy carbon electrode. Electron transfer with the immobilised POM was thoroughly investigated and compared to that of the free POM in solution.
    Chemistry 09/2013; · 5.93 Impact Factor
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    ABSTRACT: Handy POMs: Several palladium-catalyzed coupling reactions have been applied to polyoxometalate post-functionalization. The feasibility of each reaction with one model substrate was investigated and each set of synthetic conditions was optimized to obtain full conversions and high purity hybrid compounds.
    Chemistry 08/2013; · 5.93 Impact Factor
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    ABSTRACT: Steady-state irradiation under visible light of a covalent Ir(III)-photosensitized polyoxotungstate is reported. In the presence of a sacrificial electron donor, the photolysis leads to the very efficient photoreduction of the polyoxometalate. Successive formation of the one-electron and two-electron reduced species, which are unambiguously identified by comparison with spectroelectrochemical measurements, is observed with a significantly faster rate reaction for the formation of the one-electron reduced species. The kinetics of the photoreduction, which are correlated to the reduction potentials of the polyoxometalate (POM), can be finely tuned by the presence of an acid. Indeed light-driven formation of the two-electron reduced POM is considerably facilitated in the presence of acetic acid. The system is also able to perform photocatalytic hydrogen production under visible light without significant loss of performance over more than 1 week of continuous photolysis and displays higher photocatalytic efficiency than the related multi-component system, outlining the decisive effect of the covalent bonding between the POM and the photosensitizer. This functional and modular system constitutes a promising step for the development of charge photoaccumulation devices and subsequent photoelectrocatalysts for artificial photosynthesis.
    Energy & Environmental Science 05/2013; 6(5):1504-1508. · 11.65 Impact Factor
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    ABSTRACT: The coordination properties of bisorganophosphonyl and bisorganoarsenyl derivatives of heteropolytungstates towards lanthanides and early-transition-metal cations were studied in organic medium. This new class of vacant polyoxometalate (POM) hybrids proved to conserve coordination sites after the grafting of the {RP=O}2+ or {RAs=O}2+ groups onto the trivacant A,α-[PW9O34]9– and B,α-[AsW9O33]9– platforms. The consequence of the presence of free {P=O} or {As=O} groups is an increase of the hardness of the coordination sites in these anions (according to Pearson's HSAB theory). Although soft divalent transition metal cations were hardly coordinated with these hybrid monovacant POMs, complexes with hard s group (Ca2+), lanthanide (La3+, Ce3+) and d0 early-transition-metal cations were obtained and studied, in particular by single crystal X-ray diffraction. Owing to the possibility of modification of the trivacant platform, the type of the grafted function (phosphonyl or arsenyl) or the organic function R, these systems offer a unique possibility to finely modulate the coordination sphere of the cation.
    Berichte der deutschen chemischen Gesellschaft 04/2013; 2013(10‐11). · 2.94 Impact Factor
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    ABSTRACT: Keggin and Dawson-type polyoxometalates (POMs) covalently grafted to heteroleptic cyclometalated iridium(III) complexes (POM–[Ir] dyads) have been prepared by postfunctionalization of organosilyl and organotin POM derivatives. Electronic properties of these 4 photosensitized POM–[Ir] dyads were evaluated by electrochemical measurements and theoretical calculations. These studies reveal that the electron acceptor character of the POMs vary with structural class (Keggin vs. Dawson) and chemical anchorage (organosilyl vs. organotin); they reveal the poor electronic interaction between the POMs and the chromophores. Combined transient absorption and spectroelectrochemical measurements provide evidence for the formation of photoinduced electron transfer from the chromophore to the POM. The lifetimes of the charge-separated states (ranging from ns to hundreds of ns) are the longest values reported for covalently bonded photosensitized POMs. The functionalization of the heteroleptic cyclometalated iridium(III) on the picolinate ligand provides directionality to the photoinduced electron transfer by enhancing charge separation and delaying charge recombination The kinetics of the photoinduced electron transfers are rationalized by Marcus theory. We conclude that the charge separation and charge recombination respectively occur in the Marcus normal and inverted regions.
    Chemical Science 03/2013; 4(4):1737-1745. · 8.31 Impact Factor
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    ABSTRACT: Covalent grafting of heteropolyanions hybrids B,α-[As(III)W(9)O(33){P(O)(CH(2)CH(2)CO(2)H)}(2)](5-) on 3-aminopropyl functionalized SBA-15 has been achieved through the formation of peptide bonds. The covalent link has been confirmed by using IR and (13)C CP MAS NMR spectroscopies. Electrostatic interactions between carboxylate and protonated amines have been discarded on the basis of the retention of POMs after repeated washings of the resulting material by ionic liquid (bmimCl). This is the first example of anchored monovacant polyoxometalates (POM) in which nucleophilic oxygen atoms are still available after incorporation into mesoporous supports. Further characterization of the textural properties of grafted materials has shown that they still retain an important mesoporosity, which is compatible with their potential use in heterogeneous catalysis. Such systems are thus interesting candidates for the preparation of anchored homogeneous catalysts in which the POMs would play the role of polydentate inorganic ligands for the active centers.
    Inorganic Chemistry 02/2013; · 4.59 Impact Factor
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    ABSTRACT: The present study investigates the deposition of hybrid organic/inorganic monolayers composed of polyoxometalate (POM) of the Keggin-type [PW12O40]3− electrostatically linked to three alkylammonium surfactants. The surface pressure dependence, i.e. Langmuir isotherm, as well as their 2D self-assembly has been investigated with mono- and double-chained surfactants and by varying the alkyl chain length. Stable monolayers were obtained for the hexadecyltrimethylammonium and the didodecyldimethylammonium POM surfactants, called respectively C16POM and 2C12POM. It was found that increasing the surface pressure led to the formation of crystallized nano- and micro-domains in coexistence with the monolayer. The crystallites formed were monodisperse in their size repartition and showed various shapes and sizes: oblate nanoparticles of nanometric size (height ca. 7 nm, diameter ca. 140 nm) for C16POM and micrometric 2D-hexagonal crystallites for 2C12POM. The monolayers and the micro-(nano-) crystallites have been characterized after transfer on silicon wafers by means of atomic force microscopy (AFM), transmission electron microscopy (TEM) and surface-enhanced ellipsometric contrast (SEEC). High crystallinity of the hexagonal aggregates was revealed by electron diffraction (ED). For 2C12POM the monolayer formed before crystallisation is in a 2D-liquid state with the alkyl chains pointing out of the water with an average angle of the alkyl chains to the normal of the plane estimated at 50°. It is shown that the surface pressure induced crystallization of the POM surfactant results in the change of the ammonium surfactant arrangement around the POM with the alkyl chains pointing up and down the POM units showing a reverse bilayer-like structure. This change in the ammonium surfactant arrangement in response to the increase of the surface pressure enables (i) to reduce the molecular area and (ii) the formation of a 2D-hexagonal crystalline lattice of POM units. On the other hand for C16POM the formation of oblate nanoparticles is driven by a three-dimensional growth at the water surface.
    CrystEngComm 11/2012; 14(24):8446-8453. · 3.88 Impact Factor
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    ABSTRACT: Four novel hexanuclear manganese(III) complexes based on derivatized salicylamidoximes, [MnIII6(μ3-O)2(O2CPh)2(Me2N-sao)6(EtOH)4] (1), [MnIII6(μ3-O)2(O2CPh)2(Me2N-sao)6(iPrOH)4] (2), [MnIII6(μ3-O)2(O2CPh)2(Et2N-sao)6(EtOH)4] (3) and [MnIII6(μ3-O)2(O2CPh)2(Et2N-sao)6(iPrOH)4] (4) (Me2N-Hsao = dimethylsalicylamidoxime; Et2N-Hsao = diethylsalicylamidoxime), have been prepared and characterized. Single-crystal X-ray diffraction allows one to determine that 1·2CHCl3 and 4 crystallize in the triclinic system with space group P(–1), whereas 3 crystallizes in the monoclinic system with space group P21/n. dc and ac magnetic susceptibility measurements of 1-4 reveal ferromagnetic coupling between Mn(III) metal ions and single-molecule magnet behaviour. The anisotropy barriers are 56, 52, 71 and 59 K for 1, 2, 3 and 4, respectively.RésuméQuatre nouveaux complexes hexanucléaires de manganèse(III) dérivés de salicylamidoximes substituées, [MnIII6(μ3-O)2(O2CPh)2(Me2N-sao)6(EtOH)4] (1), [MnIII6(μ3-O)2(O2CPh)2(Me2N-sao)6(iPrOH)4] (2), [MnIII6(μ3-O)2(O2CPh)2(Et2N-sao)6(EtOH)4] (3) et [MnIII6(μ3-O)2(O2CPh)2(Et2N-sao)6(iPrOH)4] (4) (Me2N-Hsao = diméthylsalicylamidoxime; Et2N-Hsao = diéthylsalicylamidoxime), ont été préparés et caractérisés. La diffraction des rayons X sur monocristal montre que 1·2CHCl3 et 4 cristallisent dans le système triclinique, groupe d’espace P(–1), tandis que 3 cristallise dans le système monoclinique, groupe d’espace P21/n. La susceptibilité magnétique dc et ac de 1–4 révèle un couplage ferromagnétique entre ions Mn(III) et un comportement de molécule-aimant. Les barrières d’anisotropie sont respectivement de 56, 52, 71 et 59 K pour 1, 2, 3 and 4.
    Comptes Rendus Chimie. 10/2012; 15(10):889–894.
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    ABSTRACT: Decyl-, dodecyl-, and tetradecyltrimethylammonium cations were combined with the catalytic polyoxometalate [PW(12) O(40) ](3-) anion to give spherical and monodisperse nanoparticles that are able to stabilize emulsions in the presence of water and an aromatic solvent. This triphasic liquid/solid/liquid system, based on a catalytic surfactant, is particularly efficient as a reaction medium for epoxidation reactions that involve hydrogen peroxide. The reactions proceed at competitive rates with straightforward separation of the phases by centrifugation. Such catalytic "Pickering" emulsions combine the advantages of heterogeneous catalysis and biphasic catalysis without the drawbacks (e.g., catalyst leaching or separation time).
    Chemistry 09/2012; 18(45):14352-8. · 5.93 Impact Factor
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    ABSTRACT: Salicylamidoxime was used to synthesize 13 new polynuclear Mn(III) complexes. We present the crystallographic structures, the magnetic susceptibility and the magnetization measurements of eight of them (1-8) with the general formula [Mn(6)O(2)(H(2)N-sao)(6)(L)(2)(solvent)(4-6)] (L = carboxylate, chloride, 2-cyanophenolate; solvent = H(2)O, MeOH, EtOH, py). These complexes consist of two trinuclear {Mn(III)(3)(μ(3)-O)(H(2)N-sao)(3)}(+) cationic units linked together via two oximate and two phenolate oxygen atoms. All behave as single-molecule magnets, with the spin ground state varying from 4 to 12 and anisotropy energy barriers from 24 to 86 K, the latter being as high as the present record barrier in the Mn(6) complexes. DFT calculations were performed to compute the exchange magnetic coupling constants J between the metallic ions and to provide an orbital interpretation of exchange. Our results are in line with previously reported results with the parent salicylaldoxime derivatives. The Mn-N-O-Mn torsion angle appears as the main parameter controlling the J values. The critical angle where the exchange coupling between two Mn(III) switches from antiferromagnetic to ferromagnetic is 27°, less than the one found in related complexes with salicylaldoxime (30°). We propose a structural classification of the {Mn(6)} complexes in four classes depending on the coordination of the axial carboxylate. The work points out the structural flexibility of such systems, their sensitivity to solvent effects and their ability to achieve high anisotropy energy barriers by simple desolvation.
    Dalton Transactions 08/2012; 41(44):13668-81. · 3.81 Impact Factor
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    ABSTRACT: Polyoxometalates (POMs) have remarkable properties and a great deal of potential to meet contemporary societal demands regarding health, environment, energy and information technologies. However, implementation of POMs in various functional architectures, devices or materials requires a processing step. Most developments have considered the exchange of POM counterions in an electrostatically driven approach: immobilization of POMs on electrodes and other surfaces including oxides, embedding in polymers, incorporation into Layer-by-Layer assemblies or Langmuir-Blodgett films and hierarchical self-assembly of surfactant-encapsulated POMs have thus been thoroughly investigated. Meanwhile, the field of organic-inorganic POM hybrids has expanded and offers the opportunity to explore the covalent approach for the organization or immobilization of POMs. In this critical review, we focus on the use of POM hybrids in selected fields of applications such as catalysis, energy conversion and molecular nanosciences and we endeavor to discuss the impact of the covalent approach compared to the electrostatic one. The synthesis of organic-inorganic POM hybrids starting from bare POMs, that is the direct functionalization of POMs, is well documented and reliable and efficient synthetic procedures are available. However, as the complexity of the targeted functional system increases a multi-step strategy relying on the post-functionalization of preformed hybrid POM platforms could prove more appealing. In the second part of this review, we thus survey the synthetic methodologies of post-functionalization of POMs and critically discuss the opportunities it offers compared to direct functionalization.
    Chemical Society Reviews 07/2012; 41(22):7605-22. · 24.89 Impact Factor
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    ABSTRACT: Surface nanostructuration was successfully achieved by binding the polyoxometalate (POM) (NBu4)3[PW11O39{(SiC6H4NH2)2O}] covalently onto planar gold surfaces. To do so, POMs functionalized with two terminal amino groups were synthesized and reacted with a mercaptoundecanoic acid self-assembled monolayer adsorbed on gold. These amine-terminated POM macroanions proved to be remarkably efficient as nanostructuring agents. Using polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), conditions were optimized to elaborate a dense and well-dispersed layer of POMs, leaving a “free” amine function for the further linkage of proteins. Antirabbit immunoglobulins (anti-rIgGs) were thus grafted on the POM-structured layer, and the recognition of their specific target, rabbit immunoglobulin (rIgGs), was tested by using a quartz crystal microbalance with dissipation measurement (QCM-D). The recognition was good and highly specific, indicating that an efficient, nanostructured biosensor has been constructed. The method reported herein can be easily applied, not requiring any sophisticated experimental setup, and is promising for the patterning of any molecular probes bearing amine groups.
    The Journal of Physical Chemistry C. 06/2012; 116(24):13217–13224.
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    ABSTRACT: A novel heteroleptic cyclometalated iridium(III) complex with one picolinic acid derivative bearing a pendant terminal alkynyl tether has been prepared following a new synthetic route. This pendant alkynyl tether can be further engaged in palladium C?C coupling reactions, allowing its grafting to a Keggin-type polyoxometalate and thus providing a unique iridio-POM conjugate.
    Organometallics 01/2012; 31(1):35-38. · 4.15 Impact Factor

Publication Stats

613 Citations
464.14 Total Impact Points

Institutions

  • 1992–2014
    • Pierre and Marie Curie University - Paris 6
      • Institut Parisien de Chimie Moléculaire (IPCM)
      Lutetia Parisorum, Île-de-France, France
  • 2011–2012
    • Institut Universitaire de France
      Lutetia Parisorum, Île-de-France, France
  • 2009–2011
    • UPMC
      Pittsburgh, Pennsylvania, United States
  • 2008–2011
    • Université de Montréal
      • Department of Chemistry
      Montréal, Quebec, Canada
  • 2009–2010
    • Polytech Paris-UPMC
      Lutetia Parisorum, Île-de-France, France
    • Emory University
      • Department of Chemistry
      Atlanta, Georgia, United States
  • 2008–2009
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2003
    • Kansas State University
      • Department of Chemistry
      Manhattan, KS, United States
    • CSU Mentor
      • Department of Chemistry
      Long Beach, California, United States