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  • Y. Ren, J. Forte, K. Cheaib, N. Vanthuyne, L. Fensterbank, H. Vezin, M. Orio, S. Blanchard, et M. Desage-El Murr, « Optimizing Group Transfer Catalysis by Copper Complex with Redox-Active Ligand in an Entatic State », Iscience, vol. 23, nᵒ 3, p. UNSP 100955, mars 2020.
    Résumé : Metalloenzymes use earth-abundant non-noble metals to perform high-fidelity transformations in the biological world. To ensure chemical efficiency, metalloenzymes have acquired evolutionary reactivity-enhancing tools. Among these, the entatic state model states that a strongly distorted geometry induced by ligands around a metal center gives rise to an energized structure called entatic state, strongly improving the reactivity. However, the original definition refers both to the transfer of electrons or chemical groups, whereas the chemical application of this concept in synthetic systems has mostly focused on electron transfer, therefore eluding chemical transformations. Here we report that a highly strained redox-active ligand enables a copper complex to perform catalytic nitrogen- and carbon-group transfer in as fast as 2 min, thus exhibiting a strong increase in reactivity compared with its unstrained analogue. This report combines two reactivity-enhancing features from metalloenzymes, entasis and redox cofactors, applied to group-transfer catalysis.
    Mots-clés : aziridination, cu, E-POM, galactose-oxidase, generation, MACO, metal-complexes, models, oxidation, POLE 1, POLE 2, radicals, reactivity, site.
    Pièce jointe Texte intégral 19.8 Mo (source)

  • R. Salles, B. Abécassis, E. Derat, D. Brouri, A. Bernard, Q. Zhang, A. Proust, C. Desmarets, et G. Izzet, « Hierarchical Self-Assembly of Polyoxometalate-Based Organo Palladium(II) Metallomacrocycles via Electrostatic Interactions », Inorganic Chemistry, vol. 59, nᵒ 4, p. 2458-2463, févr. 2020.
    Résumé : The design and synthesis of a supramolecular square composed of polyoxometalate-based hybrid donors and ethylenediamine palladium(II) nodes are reported. The structure of the metallomacrocycle scaffold was inferred by diffusion NMR, small-angle X-ray scattering (SAXS), and molecular modeling. The metallomacrocycle scaffold that contains negatively and positively charged subunits can further self-assemble owing to a competition between the solvation energy of the discrete species and intermolecular electrostatic interactions. When the dissociating character of the solvent was lowered or when in the presence of a protic solvent, different types of multiscale organizations (vesicles and pseudo-1D structures) were selectively formed and were characterized by SAXS and transmission electron microscopy.
    Mots-clés : ARC, E-POM, MACO, POLE 1, POLE 2.
    Pièce jointe Full Text PDF 2.1 Mo (source)


  • Q. Arnoux, C. Blouzon, D. Li, Y. J. Dappe, A. Smogunov, P. Bonville, L. Tortech, et J. - B. Moussy, « Controlling the magnetic exchange coupling in hybrid heterojunctions via spacer layers of π-conjugated molecules », Physical Review B, vol. 99, nᵒ 14, p. 144405, avr. 2019.
    Résumé : Mastering and understanding the magnetic couplings between magnetic electrodes separated by organic layers are crucial for developing new hybrid spintronic devices. We study the magnetic exchange interactions in organic-inorganic heterojunctions and unveil the possibility of controlling the strength of the magnetic exchange coupling between two ferromagnetic electrodes across π-conjugated molecules’ (α-sexithiophene or para-sexiphenyl) ultrathin film. In Fe3O4/π-conjugated molecules/Co magnetic tunnel junctions, an antiferromagnetic interlayer exchange coupling with variable strength is observed according to the nature of the aromatic rings (thiophene or phenyl groups). The underlying physical mechanism is revealed by ab initio calculations relating the strength of magnetic coupling to the spin moment penetration into a molecular layer at the molecule/Co interface. The prospect that magnetic coupling between two ferromagnetic electrodes can be mediated and tuned by organic molecules opens different perspectives in the way magnetization of organic tunnel junctions or spin valves can be driven.
    Mots-clés : E-POM, POLE 2.
    Pièce jointe Full Text PDF 4.6 Mo (source)

  • L. Ben Haj Hassen, S. Dhifaoui, Y. Rousselin, V. Marvaud, C. Stern, C. E. Schulz, et H. Nasri, « New insights on the electronic, magnetic, electric and molecular structure of a bis-(4-cyanopyridine) iron(III) complex with the meso-tetrakis(4-methoxyphenyl)porphyrin », Inorganica Chimica Acta, vol. 486, p. 675-683, févr. 2019.
    Résumé : We have successfully synthesized and characterized a new low-spin iron(III) bis(4-cyanopyridine) complex with a meso-porphyrin substituted in the para positions of the phenyls by the methoxy group, namely the bis(4-cyanopyridine)[(meso-tetrakis(4-metoxyphenylporphyrinato)]iron(III) trifluoromethanesulfonate chlorobenzene monosolvate complex with the formula [FeIII(TMPP)(4-CNpy)2]SO3CF3.C6H5Cl (I). This species was characterized through ultraviolet–visible, Fourier-transform infrared and Mössbauer spectroscopy as well as by SQUID magnetometry, cyclic voltammetry, and X-ray crystallography. These characterizations indicated that our synthetic heme model is a low-spin (S = 1/2) coordination compound and especially shows that the structural, electronic and the magnetic properties of complex (I) are closely dominated by the presence of the methoxy σ-donor group at the para positions of the meso-porphyrin.
    Mots-clés : Cyclic voltammetry, E-POM, Iron(III) porphyrin, Magnetic properties, POLE 2, X-ray Molecular structure.

  • R. Breitwieser, A. Garnier, T. Auvray, A. - T. Ngo, B. Baptiste, N. Menguy, A. Proust, C. Petit, F. Volatron, et C. Salzemann, « Protective Effect of Polyoxometalates in {Mo132}/Maghemite Binary Superlattices Under Annealing », Frontiers in Chemistry, vol. 7, 2019.
    Résumé : The binary assembly DDA-{Mo132} / OA-γ-Fe2O3 (DDA=didodecyldimethylammonium, {Mo132}=[Mo132O372(CH3COO)30(H2O)72]42-, OA = oleic acid) constitutes one of the two examples in the literature of binary superlattices made of a mixing of nanocrystals and oxo-clusters. In a precedent work, we reported in details the preparation of such magnetic binary systems and studied the effect of the nature of the polyoxometalates (POMs) on the magnetic properties. In the present paper, we study the stability of this model binary assembly under heating at various temperatures. Indeed, especially if magnetic and/or transport properties are targeted, an annealing can be essential to change the phase of the nanocrystals in a more magnetic one and/or to desorb the organic capping of the nano-objects that can constitute an obstacle to the electronic communication between the nano-objects. The binary assembly showed a good stability at temperatures until around 400°C under vacuum thanks to the presence of the POMs that permits to avoid the aggregation of the nanocrystals as well as preserve their periodical arrangement. On the contrary, an assembly made of pure γ-Fe2O3 nanocrystals displays a clear aggregation of the nano-objects from 370°C, as attested by transmission and scanning electronic microscopies and confirmed by magnetic measurements. The stability of such POMs/nanocrystals assemblies opens the way to (i) the elaboration of new binary assemblies from POMs and numerous kinds of nanocrystals with a good control on the magnetic properties and to (ii) the investigation of new physical properties as exchange coupling, or magneto-transport in such systems.
    Mots-clés : annealing, binary superlattices, E-POM, Maghemite, magnetism, POLE 2, Polyoxometalate.
    Pièce jointe Full Text PDF 1.1 Mo (source)

  • K. D. Francesca, S. Lenfant, M. Laurans, F. Volatron, G. Izzet, V. Humblot, C. Methivier, D. Guerin, A. Proust, et D. Vuillaume, « Charge transport through redox active [H7P8W48O184]33− polyoxometalates self-assembled onto gold surfaces and gold nanodots », Nanoscale, vol. 11, nᵒ 4, p. 1863-1878, janv. 2019.
    Résumé : Polyoxometalates (POMs) are redox-active molecular oxides, which attract growing interest for their integration into nano-devices, such as high-density data storage non-volatile memories. In this work, we investigated the electrostatic deposition of the negatively charged [H7P8W48O184]33− POM onto positively charged 8-amino-1-octanethiol self-assembled monolayers (SAMs) preformed onto gold substrates or onto an array of gold nanodots. The ring-shaped [H7P8W48O184]33− POM was selected as an example of large POMs with high charge storage capacity. To avoid the formation of POM aggregates onto the substrates, which would introduce variability in the local electrical properties, special attention has to be paid to the preformed SAM seeding layer, which should itself be deprived of aggregates. Where necessary, rinsing steps were found to be crucial to eliminate these aggregates and to provide uniformly covered substrates for subsequent POM deposition and electrical characterizations. This especially holds for commercially available gold/glass substrates while these rinsing steps were not essential in the case of template stripped gold of very low roughness. Charge transport through the related molecular junctions and nanodot molecule junctions (NMJs) has been probed by conducting-AFM. We analyzed the current–voltage curves with different models: electron tunneling though the SAMs (Simmons model), transition voltage spectroscopy (TVS) method or molecular single energy level mediated transport (Landauer equation) and we discussed the energetics of the molecular junctions. We concluded to an energy level alignment of the alkyl spacer and POM lowest occupied molecular orbitals (LUMOs), probably due to dipolar effects.
    Mots-clés : E-POM, POLE 2.
    Pièce jointe Full Text PDF 4.3 Mo (source)

  • P. Galiyeva, H. Alem, H. Rinnert, L. Balan, S. Blanchard, G. Medjahdi, B. Uralbekov, et R. Schneider, « Highly fluorescent, color tunable and magnetic quaternary Ag–In–Mn–Zn–S quantum dots », Inorganic Chemistry Frontiers, vol. 6, nᵒ 6, p. 1422-1431, juin 2019.
    Résumé : Mn-Doped quantum dots (QDs) are of high interest for numerous applications like solar cells, optoelectronics, optosensing, or bioimaging. Here, we report the preparation of quaternary (AgInS2)x(MnS)y(ZnS)1−x−y QDs, thereafter noted Mn : AIZS via a thermally induced decomposition of Ag, In, Zn and Mn precursors in the presence of oleylamine and dodecanethiol. The Mn : AIZS QDs have an average diameter of 3.5 nm and their XRD patterns can be indexed with the orthorhombic phase of AgInS2. The incorporation of Mn2+ ions in the AIZS crystal lattice results in a red-shift of the photoluminescence (PL) emission maximum depending on the Mn2+ content. The PL quantum yields decrease upon loading with Mn2+ but remained high (53–31%) until 50% theoretical loading in Mn2+. Steady state, PL excitati

    on and time-resolved PL measurements suggest that Mn2+-dependent trap states are involved in the PL emission. Mn : AIZS QDs exhibit also magnetic properties. In addition, Mn : AIZS QDs can easily be transferred to the aqueous phase using the PMAO amphiphilic polymer without alteration of their optical properties (PL quantum yield up to 51%), revealing their high potential for biological applications.
    Mots-clés : E-POM, POLE 2.

  • M. Girardi, D. Platzer, S. Griveau, F. Bedioui, S. Alves, A. Proust, et S. Blanchard, « Assessing the Electrocatalytic Properties of the Cp*RhIII2+-Polyoxometalate Derivative [H2PW11O39RhIIICp*(OH2)]3– towards CO2 Reduction », European Journal of Inorganic Chemistry, vol. 2019, nᵒ 3-4, p. 387-393, 2019.
    Résumé : Storage of electricity produced intermittently by renewable energy sources is a societal issue. Besides the use of batteries and supercapacitors, conversion of excess electricity into chemical energy is also actively investigated. The conversion of CO2 to fuel or fuel precursors is an option that requires the use of a catalyst to overcome the high activation energy barrier. Of molecular catalysts, metal complexes with polypyridyl ligands are well represented, among which the [Cp*Rh(bpy)Cl]+ and [M(bpy)(CO)3X] (M = Re, Mn) complexes. As redox non-innocent ligand, the bipyridine ligand is generally involved in the reduction mechanisms. It is thus tempting to replace it by other redox non-innocent ligands such as vacant polyoxometalates (POMs). We have thus prepared [α-H2PW11O39RhIIICp*(OH2)]3– which is closely related to [Cp*RhIII(bpy)Cl]+ by substitution of the monovacant [PW11O39]7– Keggin-type POM for the bipyridine ligand. Its activity towards CO2 reduction has been assessed in acetonitrile in the presence of water. Compared to [Cp*Rh(bpy)Cl]+ that produces formate selectively over CO and H2, the POM derived catalyst favors proton reduction over CO2 reduction.
    Mots-clés : Carbon dioxide fixation, CSOB, E-POM, Non-innocent ligands, POLE 2, POLE 3, Polyoxometalates, Redox chemistry.
    Pièce jointe Full Text PDF 974.1 ko (source)

  • O. Makrygenni, F. L. Bentaleb, D. Brouri, A. Proust, F. Launay, et R. Villanneau, « Selective uptake of La3+ ions with polyoxometalates-functionalized mesoporous SBA-15: An EXAFS study », Microporous and Mesoporous Materials, vol. 287, p. 264-270, oct. 2019.
    Résumé : In this work, mesoporous materials based on inorganic/organic polyoxometalate (POMs) hybrids with the ability of further incorporating heterometallic lanthanum cations were designed. On the basis of the La3+ coordination to vacant organophosphonyle derivatives of POMs previously studied, herein POMs-grafted onto an amino-functionalized mesoporous SBA-15 ({NH2}-SBA-15) with incorporated La3+ ions were synthesized by varying the amounts of the latter. LIII-edge La EXAFS spectroscopy of the resulting materials provided local structural information around LaIII ions (i.e. number, nature and distances of neighboring atoms), which are comparable to that of the LaIII complexes of POMs hybrids. This technique, in addition with 31P CP-MAS NMR spectroscopy, gave definitive clues for a selective uptake of the incorporated La3+ ions by the POMs grafted onto the {NH2}-SBA-15 supports. This study is a clear demonstration that, due to their chelate effect, POMs hybrids act as efficient ligands for La3+ even in the presence of competitive adsorption sites. Consequently, a regular distribution of the La3+ ions along the channels of the SBA-15 is thus observed in these materials due to the nanostructuration of the POMs onto the support.
    Mots-clés : E-POM, EXAFS, Lanthanum, Mesoporous silica, POLE 2, Polyoxometalates.

  • O. Makrygenni, D. Brouri, A. Proust, F. Launay, et R. Villanneau, « Immobilization of polyoxometalate hybrid catalysts onto mesoporous silica supports using phenylene diisothiocyanate as a cross-linking agent », Microporous and Mesoporous Materials, vol. 278, p. 314-321, avr. 2019.
    Résumé : The hybrid derivative of heteropolytungstate bearing two aniline groups, namely (nBu4N)3[NaHPW9O34{As(O)C6H4NH2}2], was post-functionalized in the presence of 1,4-phenylene diisothiocyanate (PDITC). The resulting molecular moiety was characterized by IR, 1H and 31P NMR spectroscopy. In a second step, this post-functionalized hybrid of polyoxometalate was covalently grafted onto the surface of an amino-functionalized SBA-15 silica by means of the formation of thiourea bonds. This simple and efficient strategy of immobilization did not require the use of a coupling agent and was performed in mild reaction conditions. Various physicochemical techniques (13C and 31P CPMAS NMR spectroscopies, XPS, XRF, HR-TEM microscopy and N2 sorption) contributed to the full characterization of the supported catalyst. In addition HR-TEM was found to be an essential technique for the identification of the polyoxometalate units inside the pores of SBA-15. Finally, the catalytic performances of the supported polyoxometalates were evaluated in the epoxidation of cyclooctene with aqueous H2O2 in acetonitrile at 50 °C.
    Mots-clés : Anchored homogeneous catalysts, E-POM, Epoxidation catalysis, Functionalized mesoporous silica materials, POLE 2, Polyoxometalate hybrids.

  • J. Qu, C. Livache, B. Martinez, C. Gréboval, A. Chu, E. Meriggio, J. Ramade, H. Cruguel, X. Z. Xu, A. Proust, F. Volatron, G. Cabailh, N. Goubet, et E. Lhuillier, « Transport in ITO Nanocrystals with Short- to Long-Wave Infrared Absorption for Heavy-Metal-Free Infrared Photodetection », ACS Applied Nano Materials, vol. 2, nᵒ 3, p. 1621-1630, mars 2019.
    Résumé : Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices, especially in the infrared range. However, the driving materials reaching infrared absorption generally contain heavy metals (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short-, mid-, and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progress has been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles present an intraband absorption in the mid-infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1–3 × 10–13 cm2 range. We have observed that the nanocrystals can be made conductive and photoconductive thanks to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We present evidence that the observed photoresponse in the infrared is the result of a bolometric effect.
    Mots-clés : E-POM, POLE 2.
    Pièce jointe Full Text PDF 4.3 Mo (source)

  • M. Rupp, T. Auvray, E. Rousset, G. M. Mercier, V. Marvaud, D. G. Kurth, et G. S. Hanan, « Photocatalytic Hydrogen Evolution Driven by a Heteroleptic Ruthenium(II) Bis(terpyridine) Complex », Inorganic Chemistry, vol. 58, nᵒ 14, p. 9127-9134, juill. 2019.
    Résumé : Since the initial report by Lehn et al. in 1979, ruthenium tris(bipyridine) ([Ru(bpy)3]2+) and its numerous derivatives were applied as photosensitizers (PSs) in a large panel of photocatalytic conditions while the bis(terpyridine) analogues were disregarded because of their low quantum yields and short excited-state lifetimes. In this study, we prepared a new terpyridine ligand, 4′-(4-bromophenyl)-4,4‴:4″,4‴′-dipyridinyl- 2,2′:6′,2″-terpyridine (Bipytpy) and used it to prepare the heteroleptic complex [Ru(Tolyltpy)(Bipytpy)](PF6)2 (1; Tolyltpy = 4′-tolyl-2,2′:6′,2′-terpyridine). Complex 1 exhibits enhanced photophysical properties with a higher quantum yield (7.4 × 10–4) and a longer excited-state lifetime (3.8 ns) compared to those of [Ru(Tolyltpy)2](PF6)2 (3 × 10–5 and 0.74 ns, respectively). These enhanced photophysical characteristics and the potential for PS–catalyst interaction through the peripheral pyridines led us to apply the complex for visible-light-driven hydrogen evolution. The photocatalytic system based on 1 as the PS, triethanolamine as a sacrificial donor, and cobaloxime as a catalyst exhibits sustained activity over more than 10 days under blue-light irradiation (light-emitting diode centered at 450 nm). A maximum turnover number of 764 was obtained after 12 days.
    Mots-clés : E-POM, POLE 2.

  • Z. Zhao, N. Barrett, Q. Wu, D. Martinotti, L. Tortech, R. Haumont, M. Pellen, et E. K. H. Salje, « Interaction of low-energy electrons with surface polarity near ferroelastic domain boundaries », Physical Review Materials, vol. 3, nᵒ 4, p. 043601, avr. 2019.
    Résumé : We derive surface polarity at and near ferroelastic domain boundaries from molecular dynamics simulations based on an ionic spring model. Interatomic gradient forces lead to flexoelectricity which, in turn, generates polarity at the surface and in twin boundaries. We then derive generic properties of electron scattering spectra equivalent to those observed in low-energy electron microscopy (LEEM) and mirror electron microscopy (MEM) experiments. Negatively (positively) charged surfaces reflect (attract) incident electrons with low kinetic energy. The electron images reveal the valley and ridge surface structures near the intersection of the twin boundary and the surface. Polarity in surface layers is predicted to be visible in LEEM and MEM spectra at neutral surfaces, but much less when surfaces are charged. Inward polarity reflects electrons similar to negative surface cha

    rges, and outward polarity backscatters electrons like positive surface charges. Both the polarity in the twin boundary and the physical topography scatter electrons, consistent with experimental LEEM and MEM experiments on CaTiO3 with (001) and (111) surface terminations.
    Mots-clés : E-POM, POLE 2.
    Pièce jointe Full Text PDF 9.3 Mo (source)

  • Q. Zhu, B. Paci, A. Generosi, S. Renaudineau, P. Gouzerh, X. Liang, C. Mathieu, C. Rountree, G. Izzet, A. Proust, N. Barrett, et L. Tortech, « Conductivity via Thermally Induced Gap States in a Polyoxometalate Thin Layer », The Journal of Physical Chemistry C, vol. 123, nᵒ 3, p. 1922-1930, janv. 2019.


  • F. A. Black, A. Jacquart, G. Toupalas, S. Alves, A. Proust, I. P. Clark, E. A. Gibson, et G. Izzet, « Rapid photoinduced charge injection into covalent polyoxometalate–bodipy conjugates », Chemical Science, vol. 9, nᵒ 25, p. 5578-5584, 2018.
    Mots-clés : CSOB, E-POM, POLE 2, POLE 3.

  • N. Bridonneau, P. Quatremare, H. J. von Bardeleben, J. - L. Cantin, S. Pillet, E. - E. Bendeif, et V. Marvaud, « Direct Evidence of a Photoinduced Electron Transfer in Diluted “Molybdenum-Copper” Molecular Compounds », European Journal of Inorganic Chemistry, vol. 2018, nᵒ 3-4, p. 370-377, janv. 2018.
    Résumé : For the first time, direct evidence of a photoinduced intramolecular electron transfer has been found in the “molybdenum-copper“ family of cyanide complexes that corresponds to a [MoIV–CuII]→[MoV–CuI] transition. The design and synthesis of a diluted molecular system, [Mo(Zn(1–x)Cux)2-tren] (x = 0, ε, 1, 5 and 10 %, , with ε corresponding to ppm ratio), viewed as new model compounds, have allowed good characterization of the metastable states involved in the process and provided evidence for two different mechanisms. By using squid magnetometry, EPR spectroscopy and X-ray diffraction, the results of this study have confirmed not only the photoinduced electron transfer, but also supports the light-induced excited spin state trapping effect centred on the molybdenum, thought to be due to the presence of a high-spin state (S = 1). This article provides a better understanding of the photomagnetic behaviour in Mo-Cu complexes and reveals the importance of orbital overlap to differentiate the two effects.
    Mots-clés : copper, E-POM, Electron transfer, Magentic properties, Molybdenum, Photomagnetism, POLE 2, Spin transition.
    Pièce jointe Full Text PDF 1.7 Mo (source)

  • T. Buchecker, P. Schmid, S. Renaudineau, O. Diat, A. Proust, A. Pfitzner, et P. Bauduin, « Polyoxometalates in the Hofmeister series », Chemical Communications, vol. 54, nᵒ 15, p. 1833-1836, févr. 2018.
    Résumé : We propose a simple experimental procedure based on the cloud point measurement of a non-ionic surfactant as a tool for (i) estimating the super-chaotropic behaviour of polyoxometalates (POMs) and for (ii) establishing a classification of POMs according to their affinity towards polar surfaces.
    Mots-clés : E-POM.

  • S. Dhifaoui, C. Mchiri, P. Quatremare, V. Marvaud, A. Bujacz, et H. Nasri, « Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin », Journal of Molecular Structure, vol. 1153, p. 353-359, févr. 2018.
    Résumé : In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV–visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C–H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.
    Mots-clés : E-POM, Iron(III) porphyrins, Magnetic data, POLE 2, UV–Visible, X-ray molecular structure.

  • S. Dhifaoui, S. Nasri, G. Gontard, A. C. Ghosh, Y. Garcia, C. Bonifàcio, S. Najmudin, V. Marvaud, et H. Nasri, « Synthesis, Mössbauer, cyclic voltammetry, magnetic properties and molecular structures of the low-spin iron(III) bis(pyrazine) complexes with the para-fluoro and para-chloro substituted meso-tetraphenylporphyrin », Inorganica Chimica Acta, vol. 477, p. 114-121, mai 2018.
    Résumé : Two new bis(pyrazine) iron(III) meso-porphyrin complexes are reported here: the bis(pyrazine)[5,10,15,20-tetra(para-fluoro-phenyl)porphyrinato]iron(III) triflate; [Fe(TFPP)(pyz)2]SO3CF3 (1) and the bis(pyrazine)[5,10,15,20-tetra(para-chlorophenyl)porphyrinato]iron(III) triflate; [Fe(TClPP)(pyz)2]SO3CF3 (2). The X-ray molecular structures of 1–2 show that the planes of the two pyrazine axial ligands are perpendicular and that the porphyrin macrocycles of these derivatives are very distorted, leading to a short average equatorial iron-pyrrole N atoms distance appropriate for low-spin ferric porphyrinates. The Mössbauer data of 1–2 feature relatively low values of the quadrupole splitting (ΔEQ ∼ 1.20 mm.s−1) appropriate for low-spin Fe(III) metalloporphyrin with perpendicular orientation of N-donor planar ligands. The temperature dependence of the magnetic susceptibility and the magnetization curves have shown that the results for complexes 1–2 confirm the low-spin state of our two-ferric species, while the cyclic voltammetry data show that the half potential [Fe(III)/Fe(II)] values are shifted anodically compared to the β-pyrrole substituted porphyrin octaethylporphyrin with parallel bis(N-donor) planar axial ligands.
    Mots-clés : E-POM, Iron(III) porphyrins, Magnetic properties, Mössbauer, POLE 2, UV-visible, X-ray molecular structure.

  • B. Doistau, L. Benda, B. Hasenknopf, V. Marvaud, et G. Vives, « Switching Magnetic Properties by a Mechanical Motion », Magnetochemistry, vol. 4, nᵒ 1, p. 5, mars 2018.
    Résumé : Switching magnetic properties have attracted a wide interest from inorganic chemist for the objectives of information storage and quantum computing at the molecular level. This review is focused on magnetic switches based on a mechanical motion, which is an innovative approach. Three main strategies to control magnetic properties by a mechanical motion have been developed in the literature and will be described. The first one (ligand-induced spin change) consists in modulating the ligand field strength by a configuration change of the ligand in spin-crossover complexes. The second one (coordination-induced spin-state switching) is based on a change in the coordination number of a metallic center that is triggered by the motion of one ligand. The third one uses the modulation of the exchange interaction between two spin-centers by a mechanical motion.
    Mots-clés : E-POM, GOBS, LD-CISSS, LD-LISC, magnetism, molecular machine, molecular switch, photoisomerization, POLE 2, POLE 3, spin crossover.
    Pièce jointe Full Text PDF 3.4 Mo (source)

  • S. Hupin, H. Lavanant, S. Renaudineau, A. Proust, G. Izzet, M. Groessl, et C. Afonso, « A calibration framework for the determination of accurate collision cross sections of polyanions using polyoxometalate standards », Rapid Communications in Mass Spectrometry, vol. 32, nᵒ 19, p. 1703-1710, 2018.
    Résumé : Rationale Polyoxometalates (POMs) are remarkable oxo-clusters forming compact highly charged anions. We measured their collision cross sections (CCS) in N2 with drift tube ion mobility spectrometry (DTIMS). These values were then used to calibrate a traveling wave ion mobility spectrometry (TWIMS) device and the accuracy of the calibration was tested. Methods Six POM standards were analyzed by DTIM-MS (Tofwerk, Thun, Switzerland) at different voltages to determine absolute DTCCS (N2) values. Five POM compounds (Lindqvist TBA2Mo6O19; decatungstate TBA4W10O32; Keggin TBA3PMo12O40; TBA3PW12O40 and Dawson TBA6P2W18O62) were used for the calibration of the TWIM-MS instrument (Synapt G2 HDMS, Waters, Manchester, UK) and a sixth Dawson POM, TBA9P2Nb3W15O62, was used to compare the accuracy of the calibrations with POM or with polyalanine and dextran reference ions. Results We determined 45 DTCCS (N2) values at 30°C or 60°C. Fourteen DTCCS (N2) values at 30°C were used to perform calibration of the TWIMS instrument. Better correlations were observed than when DTCCS values in helium from the literature were used. The accuracy tests on six ions of Dawson POM TBA9P2Nb3W15O62 led to relative errors below 3.1% while relative errors of 3.6% to 10.1% were observed when calibration was performed with polyalanine and dextran reference ions. Conclusions Our novel calibration strategy for determination of CCS values of multiply negatively charged ions on TWIM-MS devices based on DTCCS (N2) of standard POM structures covered a wider range of CCS and improved the accuracy to 2.1% relative error on average compared with 6.9% using polyalanine and dextran calibration.
    Mots-clés : E-POM.
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  • M. Laurans, K. D. Francesca, F. Volatron, G. Izzet, D. Guerin, D. Vuillaume, S. Lenfant, et A. Proust, « Molecular signature of polyoxometalates in electron transport of silicon-based molecular junctions », Nanoscale, vol. 10, nᵒ 36, p. 17156-17165, sept. 2018.
    Résumé : Polyoxometalates (POMs) are unconventional electro-active molecules with a great potential for applications in molecular memories, providing efficient processing steps onto electrodes are available. The synthesis of the organic–inorganic polyoxometalate hybrids [PM11O39{Sn(C6H4)CC(C6H4)N2}]3− (M = Mo, W) endowed with a remote diazonium function is reported together with their covalent immobilization onto hydrogenated n-Si(100) substrates. Electron transport measurements through the resulting densely-packed monolayers contacted with a mercury drop as a top electrode confirms their homogeneity. Adjustment of the current–voltage curves with the Simmon's equation gives a mean tunnel energy barrier ΦPOM of 1.8 eV and 1.6 eV, for the Silicon–Molecules–Metal (SMM) junctions based on the polyoxotungstates (M = W) and polyoxomolybdates (M = Mo), respectively. This follows the trend observed in the electrochemical properties of POMs in solution, the polyoxomolybdates being easier to reduce than the polyoxotungstates, in agreement with lowest unoccupied molecular orbitals (LUMOs) of lower energy. The molecular signature of the POMs is thus clearly identifiable in the solid-state electrical properties and the unmatched diversity of POM molecular and electronic structures should offer a great modularity.
    Mots-clés : E-POM.
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  • O. Makrygenni, E. Secret, A. Michel, D. Brouri, V. Dupuis, A. Proust, J. - M. Siaugue, et R. Villanneau, « Heteropolytungstate-decorated core-shell magnetic nanoparticles: A covalent strategy for polyoxometalate-based hybrid nanomaterials », Journal of Colloid and Interface Science, vol. 514, p. 49-58, mars 2018.
    Résumé : Amino-functionalized core–shell magnetic nanoparticles have been covalently grafted with Polyoxometalates (POMs). These multifunctional nanocomposites have been obtained through the coupling of heteropolytungstate-based hybrids bearing carboxylic acid functions with aminopropyl functions that decorate the core–shell nanoparticles. The physical properties of the resulting materials have been studied by a large set of techniques. The very good nanostructuration of the POMs at the surface of the obtained nanoparticles have thus been directly observed by high-resolution transmission electronic microscopy (HR-TEM). Furthermore, the hyperthermia properties of these nanocomposites have been also considered as a function of the size of the magnetic core. Finally, the stability of these suspensions in organic media makes them particularly interesting in the frame of their processing or their potential use as nanocatalysts.
    Mots-clés : Core-shell nanoparticles, E-POM, HR-TEM, Hybrid materials, POLE 2, Polyoxometalates.

  • B. Martinez, C. Livache, E. Meriggio, X. Z. Xu, H. Cruguel, E. Lacaze, A. Proust, S. Ithurria, M. G. Silly, G. Cabailh, F. Volatron, et E. Lhuillier, « Polyoxometalate as Control Agent for the Doping in HgSe Self-Doped Nanocrystals », The Journal of Physical Chemistry C, vol. 122, nᵒ 46, p. 26680-26685, nov. 2018.
    Résumé : Intraband and plasmonic transitions have appeared over the last years as an interesting tool to achieve optical absorption in the mid-infrared. Tuning the doping magnitude has become a major challenge not only to tune the optical spectrum but also properties such as the dark current or the time response. Here, we investigate the case of self-doped HgSe colloidal quantum dots (CQDs). At present, tuning of the doping relies on band bending induced by a dipole design at the nanoparticle surface. With such a surface gating approach, it is difficult to conciliate both massive tuning of the Fermi level and the preservation of transport properties of the CQD arrays. Here, we propose a strategy to graft functionalized polyoxometalates (POMs) at the CQD surface and obtain simultaneously a massive tuning of the carrier density (≈5 electrons per nanoparticle) and conduction properties. We bring a consistent demonstration of the HgSe CQD doping decrease by a charge transfer to the POM. This method is highly promising for large tuning of carrier density in degenerately doped semiconductor nanoparticles.
    Mots-clés : E-POM.

  • F. Mercier-Bion, J. Li, H. Lotz, L. Tortech, D. Neff, et P. Dillmann, « Electrical properties of iron corrosion layers formed in anoxic environments at the nanometer scale », Corrosion Science, vol. 137, p. 98-110, juin 2018.
    Résumé : The electrical properties of the corrosion layers on archaeological iron artefacts were determined by Conductive Atomic Force Microscopy. Different corrosion products were studied: FeII carbonates, magnetite entrapped in the carbonate, and iron sulfides. The results indicate that the ferrous carbonate matrix is insulating, and that magnetite and iron sulfides have a conductive character, although these phases are not systematically connected to the metal. This suggests that electrons produced by the anodic dissolution of metal would be conducted to the external part of the corrosion product layer through a three-dimensional network of connected magnetite strips passing through the ferrous carbonate matrix.
    Mots-clés : Archaeological artefact, C-AFM, E-POM, Electrical properties, FESEM, Iron corrosion, POLE 2, μRaman.

  • E. Nikoloudakis, K. Karikis, M. Laurans, C. Kokotidou, A. Solé-Daura, J. J. Carbó, A. Charisiadis, G. Charalambidis, G. Izzet, A. Mitraki, A. M. Douvas, J. M. Poblet, A. Proust, et A. G. Coutsolelos, « Self-assembly study of nanometric spheres from polyoxometalate-phenylalanine hybrids, an experimental and theoretical approach », Dalton Transactions, vol. 47, nᵒ 18, p. 6304-6313, mai 2018.
    Résumé : Herein, we report on the study of supramolecular assemblies based on polyoxometalates (POMs) upon their modification with amino acids. Two POM-amino acid hybrids were synthesized by coupling a functionalized Keggin type polyoxoanion [PW11O39{Sn(C6H4)CC(C6H4)COOH}]4− with carboxyl-protected (methyl-ester) phenylalanine or diphenylalanine peptides. Surprisingly, all compounds, including the initial POM, formed supramolecular nanospheres in different solvent mixtures, which were examined by scanning electron microscopy (SEM). Molecular dynamics (MD) simulations for the POM-amino acid species revealed that the hydrophobic forces are mainly responsible for the initial aggregation into incipient micelle type structures, in which the organic arms are buried inside the aggregate while POM polar heads are more exposed to the solvent with tetrabutyl-ammonium counter cations acting as linkers.
    Mots-clés : E-POM.
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  • M. Piot, B. Abécassis, D. Brouri, C. Troufflard, A. Proust, et G. Izzet, « Control of the hierarchical self-assembly of polyoxometalate-based metallomacrocycles by redox trigger and solvent composition », Proceedings of the National Academy of Sciences, vol. 115, nᵒ 36, p. 8895-8900, sept. 2018.
    Résumé : Discrete metallomacrocycles are attractive scaffolds for the formation of complex supramolecular architectures with emergent properties. We herein describe the formation of hierarchical nanostructures using preformed metallomacrocycles by coordination-driven self-assembly of a covalent organic–inorganic polyoxometalate (POM)-based hybrid. In this system, we take advantage of the presence of charged subunits (POM, metal linker, and counterions) within the metallomacrocycles, which drive their aggregation through intermolecular electrostatic interactions. We show that the solvent composition and the charge of the metal linker are key parameters that steer the supramolecular organization. Different types of hierarchical self-assemblies, zero-dime

    nsional (0D) dense nanoparticles, and 1D worm-like nanoobjects, can be selectively formed owing to different aggregation modes of the metallomacrocycles. Finally, we report that the worm-like structures drastically enhance the solubility in water of a pyrene derivative and can act as molecular carriers.
    Mots-clés : E-POM, hierarchical self-assembly, molecular carrier, organic–inorganic hybrids, polyoxometalates, SAXS.
    Pièce jointe Full Text PDF 1.1 Mo (source)

  • Y. Ren, K. Cheaib, J. Jacquet, H. Vezin, L. Fensterbank, M. Orio, S. Blanchard, et M. Desage‐El Murr, « Copper-Catalyzed Aziridination with Redox-Active Ligands: Molecular Spin Catalysis », Chemistry – A European Journal, vol. 24, nᵒ 20, p. 5086-5090, avr. 2018.
    Résumé : Small-molecule catalysts as mimics of biological systems illustrate the chemists’ attempts at emulating the tantalizing abilities displayed by nature's metalloenzymes. Among these innate behaviors, spin multistate reactivity is used by biological systems as it offers thermodynamic leverage towards challenging chemical reactivity but this concept is difficult to translate into the realm of synthetic organometallic catalysis. Here, we report a rare example of molecular spin catalysis involving multistate reactivity in a small-molecule biomimetic copper catalyst applied to aziridination. This behavior is supported by spin state flexibility enabled by the redox-active ligand.
    Mots-clés : aziridination, copper catalysis, E-POM, MACO, multistate reactivity, POLE 1, POLE 2, redox-active ligands, spin catalysis.
    Pièce jointe Full Text PDF 963.4 ko (source)

  • T. Zhang, L. Mazaud, L. - M. Chamoreau, C. Paris, A. Proust, et G. Guillemot, « Unveiling the Active Surface Sites in Heterogeneous Titanium-Based Silicalite Epoxidation Catalysts: Input of Silanol-Functionalized Polyoxotungstates as Soluble Analogues », ACS Catalysis, vol. 8, nᵒ 3, p. 2330-2342, mars 2018.
    Résumé : We report on a site-isolated model for Ti(IV) by reacting [Ti(iPrO)4] with the silanol-functionalized polyoxotungstates [XW9O34–x(tBuSiOH)3]3– (X = P, x = 0, 1; X = Sb, x = 1, 2) in tetrahydrofuran. The resulting titanium(IV) complexes [XW9O34–x(tBuSiO)3Ti(OiPr)]3– (X = P, 3; X = Sb, 4) were obtained in monomeric forms both in solution and in the solid state, as proved by diffusion NMR experiments and by X-ray crystallographic analysis. Anions 3 and 4 represent relevant soluble models for heterogeneous titanium silicalite epoxidation catalysts. The POM scaffolds feature slight conformational differences that influence the chemical behavior of 3 and 4 as demonstrated by their reaction with H2O. In the case of 3, the hydrolysis reaction of the isopropoxide ligand is only little shifted toward the formation of a monomeric [PW9O34(tBuSiO)3Ti(OH)]3– (5) species [log K = −1.96], whereas 4 reacted readily with H2O to form a μ-oxo bridged dimer {[SbW9O33(tBuSiO)3Ti]2O}6– (6). The more confined was the coordination site, the more hydrophobic was the metal complex. By studying the reaction of 3 and 4 with hydrogen peroxide using NMR and Raman spectroscopies, we concluded that the reaction leads to the formation of a titanium-hydroperoxide Ti-(η1-OOH) moiety, which is directly involved in the epoxidation of the allylic alcohol 3-methyl-2-buten-1-ol. The combined use of both spectroscopies also led to understanding that a shift of the acid–base equilibrium toward the formation of Ti(η2-O2) and H3O+ correlates with the partial hydrolysis of the phosphotungstate scaffold in 3. In that case, the release of protons also catalyzed the oxirane opening of the in situ formed epoxide, leading to an increased selectivity for 1,2,3-butane-triol. In the case of the more stable [SbW9O33(tBuSiO)3Ti(OiPr)]3– (4), the evolution to Ti(η2-O2) peroxide was not detected by Raman spectroscopy, and we performed reaction progress kinetic analysis by NMR monitoring the 3-methyl-2-buten-1-ol epoxidation to assess the efficiency and integrity of 4 as precatalyst.
    Mots-clés : E-POM, POLE 2.

  • T. Zhang, A. Solé-Daura, S. Hostachy, S. Blanchard, C. Paris, Y. Li, J. J. Carbó, J. M. Poblet, A. Proust, et G. Guillemot, « Modeling the Oxygen Vacancy at a Molecular Vanadium(III) Silica-Supported Catalyst », Journal of the American Chemical Society, vol. 140, nᵒ 44, p. 14903-14914, nov. 2018.
    Résumé : Here we report on the use of a silanol-decorated polyoxotungstate, [SbW9O33(tBuSiOH)3]3– (1), as a molecular support to describe the coordination of a vanadium atom at a single-site on silica surfaces. By reacting [V(Mes)3·thf] (Mes = 2,4,6-trimethylphenyl) with 1 in tetrahydrofuran, the vanadium(III) derivative [SbW9O33(tBuSiO)3V(thf)]3– (2) was obtained. Compound 2 displays the paramagnetic behavior expected for a d2-VIII high spin complex (SQUID measurements) with a triplet electronic ground state (ca. 30 kcal·mol–1 more stable than the singlet, from DFT calculations). Compound 2 proves to be a reliable model for reduced isolated-vanadium atom dispersed on silica surfaces [(≡Si—O)3VIII(OH2)], an intermediate that is often proposed in a Mars–van Krevelen type mechanism for partial oxidation of light alcohols. Oxidation of 2 under air produced the oxo-derivative [SbW9O33(tBuSiO)3VO]3– (3). In compound 2, the d2-electrons are localized in degenerated d(V) orbitals, whereas in the electronically analogous bireduced-[SbW9O33(tBuSiO)3VO]5–, 3·(2e), one electron is localized on d(V) orbital and the second one is delocalized on the polyoxotungstic framework, leading to a unique case of a bireduced heteropolyanion derivative with completely decoupled d1-V(IV) and d1-W(V). Our body of experimental results (EPR, magnetic measurements, spectroelectrochemical studies, Raman spectroscopy) and theoretical studies highlights (i) the role of the apical ligand coordination, i.e., thf (σ-donor) vs oxo (π-donor), in destabilizing or stabilizing the d(V) orbitals relative to the d(W) orbitals, and (ii) a geometrical distortion of the O3VO entity that causes a splitting of the degenerated orbitals and the stabilization of one d(V) orbital in the bireduced compound 3·(2e).
    Mots-clés : E-POM, ERMMES, POLE 2.


  • Q. Arnoux, A. Boucly, V. Barth, R. Benbalagh, A. Cossaro, L. Floreano, M. Silly, F. Sirotti, E. Derat, S. Carniato, F. Bournel, J. - J. Gallet, D. Fichou, L. Tortech, et F. Rochet, « Energy-Level Alignment of a Hole-Transport Organic Layer and ITO: Toward Applications for Organic Electronic Devices », ACS Applied Materials & Interfaces, vol. 9, nᵒ 36, p. 30992-31004, sept. 2017.
    Résumé : 2,2′,6,6′-Tetraphenyl-4,4′-dipyranylidene (DIPO-Ph4) was grown by vacuum deposition on an indium tin oxide (ITO) substrate. The films were characterized by atomic force microscopy as well as synchrotron radiation UV and X-ray photoelectron spectroscopy to gain an insight into the material growth and to better understand the electronic properties of the ITO/DIPO-Ph4 interface. To interpret our spectroscopic data, we consider the formation of cationic DIPO-Ph4 at the ITO interface owing to a charge transfer from the organic layer to the substrate. Ionization energy DFT calculations of the neutral and cationic species substantiate this hypothesis. Finally, we present the energetic diagram of the ITO/DIPO-Ph4 system, and we discuss the application of this interface in various technologically relevant systems, as a hole-injector in OLEDs or as a hole-collector interfacial layer adjacent to the prototypical OPV layer P3HT:PCBM.
    Mots-clés : E-POM, POLE 1, POLE 2.

  • Q. Arnoux, B. Watts, S. Swaraj, F. Rochet, et L. Tortech, « X-ray microscopic investigation of molecular orientation in a hole carrier thin film for organic solar cells », Nano Research, p. 1-12, nov. 2017.
    Résumé : As dipyranylidenes are excellent hole carriers, applications in organic solar cells or organic light emitting diode are envisaged. In the present study, we investigate the morphology of 2,2′,6,6′-tetraphenyl-4,4′-dipyranylidene (DIPO-Ph4) deposited under vacuum on a silicon nitride (Si3N4) substrate, a paradigmatic system for the study of molecular crystal/inorganic substrate interfaces. Samples with various coating ratios and different thermal treatments were prepared. The films were characterized by atomic force microscopy and scanning transmission X-ray microscopy to gain insight into material growth. The results show a change in orientation at a molecular level depending upon the evaporation conditions. We are now able to tailor an organic layer with a specific molecular orientation and a specific electronic behavior.Open image in new window
    Mots-clés : E-POM, POLE 2.
    Pièce jointe Full Text PDF 2.2 Mo (source)

  • M. Courté, M. Alaaeddine, V. Barth, L. Tortech, et D. Fichou, « Structural and electronic properties of 2,2′,6,6′-tetraphenyl-dipyranylidene and its use as a hole-collecting interfacial layer in organic solar cells », Dyes and Pigments, vol. 141, p. 487-492, juin 2017.
    Résumé : The accumulation of positive charges at the anodic interface considerably limits the efficiency of photovoltaic solar cells based on polymer/fullerene bulk heterojunctions (BHJs). Interfacial layers (IFLs) such as PEDOT:PSS improve charge injection but have no effect on the unbalanced electron/hole transport across the BHJ. We report here the use of 2,2′,6,6′-tetraphenyl-dipyranylidene (DIPO-Ph4), a planar quinoïd compound, as an efficient anodic IFL in organic solar cells based on BHJs made of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM). When deposited under vacuum onto a glass substrate, DIPO-Ph4 thin films are constituted of densely packed and vertically aligned crystalline needles. Current-sensing atomic force microscopy (CS-AFM) reveals a considerable increase of the hole-carrying pathways in DIPO-Ph4 thin films as compare to PEDOT:PSS, thus revealing their hole transporting/electron blocking properties. Inserting a 10 nm thick IFL of DIPO-Ph4 in combination with a 5 nm thick PEDOT:PSS between the ITO electrode and the P3HT:PCBM film leads to photocurrent densities up to 11.5 mA/cm2 under AM 1.5G and conversion efficiencies up to 4.6%, that is substantially higher than PEDOT:PSS-only devices.
    Mots-clés : Atomic force microscopy, Bulk heterojunction, E-POM, Hole collection, Interfacial layers, NASCO, Organic solar cells, POLE 1, POLE 2.

  • B. Doistau, L. Benda, J. - L. Cantin, L. - M. Chamoreau, E. Ruiz, V. Marvaud, B. Hasenknopf, et G. Vives, « Six states switching of redox-active molecular tweezers by three orthogonal stimuli », Journal of the American Chemical Society, juin 2017.
    Résumé : A six level molecular switch based on terpyridine(Ni-salphen)2 tweezers and addressable by three orthogonal stimuli (metal coordination, redox reaction and guest binding) is reported. By a metal coordination stimulus, the tweezers can be mechanically switched from an open “W”-shaped conformation to a closed “U”-shaped form. Theses two states can each be reversibly oxidized by the redox stimulus and bind to a pyrazine guest resulting in four additional states. All six states are stable and accessible by the right combination of stimuli and were studied by NMR, XRD, EPR spectroscopy and DFT calculations. The combination of the supramolecular concepts of mechanical motion and guest binding with the redox non-innocent and valence tautomerism properties of Ni-salphen complexes added two new dimensions to a mechanical switch.
    Mots-clés : E-POM, GOBS, POLE 2, POLE 3.

  • G. Izzet, F. Volatron, et A. Proust, « Tailor–made Covalent Organic-Inorganic Polyoxometalate Hybrids: Versatile Platforms for the Elaboration of Functional Molecular Architectures », The Chemical Record, vol. 17, nᵒ 2, p. 250-266, 2017.
    Résumé : Post-functionalization of organically modified polyoxometalates (POMs) is a powerful synthetic tool to devise functional building blocks for the rational elaboration of POM-based molecular materials. In this personal account we focus on iodoaryl-terminated POM platforms, describe reliable routes to the synthesis of covalent organic-inorganic POM-based hybrids and their integration into advanced molecular architectures or multi-scale assemblies as well as their immobilization onto surfaces. Valorisation of the remarkable redox properties of POMs in the fields of artificial synthesis and molecular electronic is especially considered.
    Mots-clés : artificial photosynthesis, E-POM, modified electrodes, organic-inorganic hybrids, palladium cross-coupling, POLE 2, Polyoxometalates.

  • J. Jacquet, K. Cheaib, Y. Ren, H. Vezin, M. Orio, S. Blanchard, L. Fensterbank, et M. Desage‐El Murr, « Circumventing Intrinsic Metal Reactivity: Radical Generation with Redox-Active Ligands », Chemistry – A European Journal, vol. 23, nᵒ 60, p. 15030-15034, oct. 2017.
    Résumé : Nickel complexes have gained sustained attention as efficient catalysts in cross-coupling reactions and co-catalysts in dual systems due to their ability to react with radical species. Central to this reactivity is nickel's propensity to shuttle through several accessible redox states from Ni0 to NiIV. Here, we report the catalytic generation of trifluoromethyl radicals from a nickel complex bearing redox-active iminosemiquinone ligands. This unprecedented reactivity is enabled through ligand-based oxidation performing electron transfer to an electrophilic CF3+ source while the nickel oxidation state is preserved. Additionally, extension of this reactivity to a copper complex bearing a single redox equivalent is reported, thus providing a unified reactivity scheme. These results open new pathways in radical chemistry with redox-active ligands.
    Mots-clés : CF3. radicals, E-POM, MACO, nickel, POLE 2, redox-active ligand, single electron transfer.
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  • G. F. Nataf, M. Guennou, J. Kreisel, P. Hicher, R. Haumont, O. Aktas, E. K. H. Salje, L. Tortech, C. Mathieu, D. Martinotti, et N. Barrett, « Control of surface potential at polar domain walls in a nonpolar oxide », Phys. Rev. Materials, vol. 1, nᵒ 7, p. 074410, 2017.

  • A. Parrot, A. Bernard, A. Jacquart, S. A. Serapian, C. Bo, E. Derat, O. Oms, A. Dolbecq, A. Proust, R. Métivier, P. Mialane, et G. Izzet, « Photochromism and Dual-Color Fluorescence in a Polyoxometalate–Benzospiropyran Molecular Switch », Angewandte Chemie International Edition, vol. 56, nᵒ 17, p. 4872-4876, 2017.
    Résumé : 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 (λem (closed form)=530 nm, λem (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.
    Mots-clés : Density functional calculations, E-POM, fluorescence, MACO, molecular photoswitches, photochromism, POLE 1, POLE 2, Polyoxometalates.

  • E. Rousset, I. Ciofini, V. Marvaud, et G. S. Hanan, « Facile One-Pot Synthesis of Ruthenium(II) Quaterpyridine-Based Photosensitizers for Photocatalyzed Hydrogen Production », Inorganic Chemistry, vol. 56, nᵒ 16, p. 9515-9524, août 2017.
    Résumé : We present here the efficient microwave-assisted synthesis and photophysical study of a family of ruthenium(II) complexes of the general formula [Ru(bpy)x(qpy)3-x]2+ (where bpy = 2,2′-bipyridine, qpy = 4,4′:2′,2″:4″,4‴-quaterpyridine, and x = 0, 1, 2 giving compounds 1 = [Ru(bpy)2(qpy)1]2+, 2 = [Ru(bpy)1(qpy)2]2+, and 3 = [Ru(qpy)3]2+). Compared to the standard reference, [Ru(bpy)3]2+ (τ = 870 ns, Φ = 9.5%), the complexes display longer-lived excited state lifetimes at room temperature (τ: 1 = 1440 ns, 2 = 1640 ns, 3 = 1780 ns) and improved quantum yields (Φ: 1 = 14%, 2 = 19%, 3 = 23%). Theoretical calculations were performed to support the interpretation of these photophysical properties. These complexes are excellent photosensitizers as they absorb light throughout the visible spectrum, have excellent excited state lifetimes at room temperature, and have high quantum yields. In combination with a cobalt dimethylglyoxime catalyst, they exhibit remarkable hydrogen evolution with blue light, and they are far more efficient than the reference in the field, [Ru(bpy)3]2+.
    Mots-clés : E-POM, POLE 2.


  • J. J. Baldoví, Y. Duan, C. Bustos, S. Cardona-Serra, P. Gouzerh, R. Villanneau, G. Gontard, J. M. Clemente-Juan, A. Gaita-Ariño, C. Giménez-Saiz, A. Proust, et E. Coronado, « Single ion magnets based on lanthanoid polyoxomolybdate complexes », Dalton Transactions, vol. 45, nᵒ 42, p. 16653 - 16660, 2016.
    Résumé : Polyoxometalate (POM) chemistry has recently offered excellent examples of single ion magnets (SIMs) and molecular spin qubits. Compared with conventional coordination compounds, POMs provide rigid and highly symmetric coordination sites. However, all POM-based SIMs reported to date exhibit a very limited range of possibilities for chemical processability. We present herein two new families of POM-based SIMs which are soluble in organic solvents: [Ln(β-Mo8O26)2]5− {LnIII = Tb, Dy, Ho, Er, Tm and Yb} and the functionalised POMs [Ln{Mo5O13(OMe)4NNC6H4-p-NO2}2]3− {LnIII = Tb, Dy, Ho, Er, Yb and Nd}. In addition, these two families represent the first SIMs based on polyoxomolybdates. A magneto-structural analysis of these families is presented, which is based on an effective crystal field model, and compared with the results reported in analogous lanthanoid SIMs based on polyoxotungstates.
    Mots-clés : E-POM, POLE 2.

  • N. Bridonneau, L. - M. Chamoreau, G. Gontard, J. - L. Cantin, J. von Bardeleben, et V. Marvaud, « A high-nuclearity metal-cyanide cluster [Mo6Cu14] with photomagnetic properties », vol. 45, nᵒ 23, p. 9412-9418, juin 2016.
    Résumé : A high-nuclearity metal-cyanide cluster [Mo6Cu14] has been prepared and its photomagnetic properties investigated. The photoswitchable magnetic phenomenon observed is thermally reversible (T ≈ 230 K). In the field of photomagnetism, [Mo6Cu14] represents a unique example of a nanocage and the highest nuclearity observed so far.
    Mots-clés : E-POM, POLE 2.

  • V. E. Campbell, M. Tonelli, I. Cimatti, J. - B. Moussy, L. Tortech, Y. J. Dappe, E. Rivière, R. Guillot, S. Delprat, R. Mattana, P. Seneor, P. Ohresser, F. Choueikani, E. Otero, F. Koprowiak, V. G. Chilkuri, N. Suaud, N. Guihéry, A. Galtayries, F. Miserque, M. - A. Arrio, P. Sainctavit, et T. Mallah, « Engineering the magnetic coupling and anisotropy at the molecule–magnetic surface interface in molecular spintronic devices », Nature Communications, vol. 7, p. 13646, déc. 2016.
    Résumé : Controlling the magnetic response of a molecular device is important for spintronic applications. Here the authors report the self-assembly, magnetic coupling, and anisotropy of two transition metal complexes bound to a ferrimagnetic surface, and probe the role of the nature of the transition metal ion.
    Mots-clés : E-POM, POLE 2.

  • S. Garai, H. Bögge, A. Merca, O. A. Petina, A. Grego, P. Gouzerh, E. T. K. Haupt, I. A. Weinstock, et A. Müller, « Densely Packed Hydrophobic Clustering: Encapsulated Valerates Form a High-Temperature-Stable {Mo132 } Capsule System », Angewandte Chemie (International Ed. in English), vol. 55, nᵒ 23, p. 6634-6637, juin 2016.
    Résumé : Porous molecular nanocontainers of {Mo132 }-type Keplerates offer unique opportunities to study a wide variety of relevant phenomena. An impressive example is provided by the highly reactive {Mo132 -CO3 } capsule, the reaction of which with valeric acid results in the very easy release of carbon dioxide and the uptake of 24 valerate ions/ligands that are integrated as a densely packed aggregate, thus indicating the unique possibility of hydrophobic clustering inside the cavity. Two-dimensional NMR techniques were used to demonstrate the presence of the 24 valerates and the stability of the capsule up to ca. 100 °C. Increasing the number of hydrophobic parts enhances the stability of the whole system. This situation also occurs in biological systems, such as globular proteins or protein pockets.
    Mots-clés : confinement effects, dense packing, E-POM, hydrophobic interactions, NMR spectroscopy, POLE 2, porous capsules.

  • L. Huder, C. Rinfray, D. Rouchon, A. Benayad, M. Baraket, G. Izzet, F. Lipp-Bregolin, G. Lapertot, L. Dubois, A. Proust, L. Jansen, et F. Duclairoir, « Evidence for Charge Transfer at the Interface between Hybrid Phosphomolybdate and Epitaxial Graphene », Langmuir, vol. 32, nᵒ 19, p. 4774-4783, 2016.
    Résumé : The interfacing of polyoxometalates and graphene can be considered to be an innovative way to generate hybrid structures that take advantage of the properties of both components. Polyoxometalates are redox-sensitive and photosensitive compounds with high temperature stability (up to 400 °C for some), showing tunable properties depending on the metal incorporated inside the complex. Graphene has a unique electronic band structure combined with good material properties for electrical and optical applications. The spontaneous, rather than electrochemical, functionalization of epitaxial graphene on SiC with Keggin phosphomolybdate derivative TBA3[PMo11O39{Sn(C6H4)C≡C(C6H4)N2}] (named KMoSn[N2+]) bearing a phenyl diazonium unit is investigated. Graphene decoration is evidenced by means of AFM, Raman, XPS, and cyclic voltammetry, indicating a successful immobilization of the polyoxomolybdate. The covalent bonding of the polyoxometalate to the graphene substrate can be deduced from the appearance of a D band in the Raman spectra and from the loss of mobility in the electrical conduction. High-resolution XPS spectra reveal an electron transfer from the graphene to the Mo complex. The comparison of charge-carrier density measurements before and after grafting supports the p-type doping effect, which is further evidenced by work function UPS measurements.
    Mots-clés : E-POM, POLE 2.

  • S. Humbert, G. Izzet, et P. Raybaud, « Competitive adsorption of nitrogen and sulphur compounds on a multisite model of NiMoS catalyst: A theoretical study », Journal of Catalysis, vol. 333, p. 78-93, janv. 2016.
    Résumé : Using density functional theory including dispersion corrections, we establish a scale of enthalpies and Gibbs energies of adsorption of various organo-nitrogen molecules on a multisite model of the NiMoS active phase, which includes coordinatively unsaturated Lewis sites (Mo or Ni) and Brønsted –SH sites located on the M-edge and S-edge. Dispersion corrections and entropic effects are shown to impact significantly Gibbs energies of adsorption. In particular, protonation of pyridine derivatives is enhanced at high temperature on the Brønsted –SH sites of the M-edge and S-edge. For pyridine, a vibrational frequency analysis of the adsorption modes is undertaken. Stable adsorption configurations are identified for thiophene and 4,6-DMDBT on Lewis and Brønsted sites, and compared to N-containing molecules. While pyrrole derivatives are weak poisons of adsorption sites, pyridine derivatives are the stronger inhibitors. Furthermore, ammonia exhibits a non-negligible inhibitor character. We finally discuss the impact of inhibitors on 4,6-DMDBT hydrodesulphurization pathways.
    Mots-clés : 4,6-Dimethyldibenzothiophene, density functional theory, E-POM, Hydrodenitrogenation, Hydrodesulphurization, Inhibition, NiMoS, Nitrogen compounds, POLE 2, Vibrational modes.

  • G. Izzet, B. Abécassis, D. Brouri, M. Piot, B. Matt, S. A. Serapian, C. Bo, et A. Proust, « Hierarchical Self-Assembly of Polyoxometalate-Based Hybrids Driven by Metal Coordination and Electrostatic Interactions: From Discrete Supramolecular Species to Dense Monodisperse Nanoparticles », Journal of the American Chemical Society, vol. 138, nᵒ 15, p. 5093-5099, 2016.
    Résumé : The metal-driven self-assembly processes of a covalent polyoxometalate (POM)-based hybrid bearing remote terpyridine binding sites have been investigated. In a strongly dissociating solvent, a discrete metallomacrocycle, described as a molecular triangle, is formed and characterized by 2D diffusion NMR spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and molecular modeling. In a less dissociating solvent, the primary supramolecular structure, combining negatively charged POMs and cationic metal linkers, further self-assemble through intermolecular electrostatic interactions in a reversible process. The resulting hierarchical assemblies are dense monodisperse nanoparticles composed of ca. 50 POMs that were characterized by SAXS and transmission electron microscopy (TEM). This multiscale organized system directed by metal coordination and electrostatic interactions constitutes a promising step for the future design of POM self-assemblies with controllable structure-directing factors.
    Mots-clés : E-POM, POLE 2.
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    J. Jacquet, S. Blanchard, E. Derat, M. D. - E. Murr, et L. Fensterbank, « Redox-ligand sustains controlled generation of CF3 radicals by well-defined copper complex », Chemical Science, vol. 7, nᵒ 3, p. 2030-2036, févr. 2016.
    Résumé : A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF3+ source into CF˙3 radicals. This redox behavior is enabled by the ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(II). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF˙3 radicals.
    Mots-clés : E-POM, MACO, POLE 1, POLE 2.

  • J. Jacquet, P. Chaumont, G. Gontard, M. Orio, H. Vezin, S. Blanchard, M. Desage-El Murr, et L. Fensterbank, « C−N Bond Formation from a Masked High-Valent Copper Complex Stabilized by Redox Non-Innocent Ligands », Angewandte Chemie International Edition, vol. 55, nᵒ 36, p. 10712-10716, 2016.
    Résumé : The reactivity of a stable copper(II) complex bearing fully oxidized iminobenzoquinone redox ligands towards nucleophiles is described. In sharp contrast with its genuine low-valent counterpart...
    Mots-clés : E-POM, MACO, POLE 1, POLE 2.

  • A. Lombana, C. Rinfray, F. Volatron, G. Izzet, N. Battaglini, S. Alves, P. Decorse, P. Lang, et A. Proust, « Surface Organization of Polyoxometalate Hybrids Steered by a 2D Supramolecular PTCDI/Melamine Network », The Journal of Physical Chemistry C, vol. 120, nᵒ 5, p. 2837-2845, 2016.
    Résumé : A 2D supramolecular honeycomb network built on hydrogen bonding of perylene-3,4,9,10-tetracarboxylic acid diimide (PTCDI) and 1,3,5-triazine-2,4,6-triamine (Melamine) has been self-assembled on Au(111) by a solution processed method. The ability of the porous network to host functional molecular oxides or polyoxometalates (POMs) has been investigated using a functionalized species [PW11O39Ge{p-C6H4-C≡C–C6H4-NHC(O) (CH2)4{-CH(CH2)2S-S-}}]4– (KWGe[S-S]): this inorganic/organic hybrid built on a Keggin-type POM core and an organic tether incorporating a thioctic acid function has been designed to enhance the host–guest interaction by the formation of covalent Au–S bonds. XPS analysis confirmed the presence of the POMs that are covalently held onto the surface. Probed by STM operating under ambient conditions, the spatial organization of the POMs display some reminiscence of the organic template, while monitoring the POM deposition at various immersion times by PM-IRRAS showed that the POM raising at the substrate is fostered.
    Mots-clés : CSOB, E-POM, POLE 2, POLE 3.

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