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International audience; Microporous ceria thin films having nanocrystallites network were synthesized by evaporation-induced self-assemblyprocess, using P123 amphiphilic copolymer as structure-directing agent. The impact of key experimental parameters,i.e., the sol ageing, the relative humidity (RH), the thermal treatment, on the thin layer elaboration were investigated.The results show that the organization of the nanoparticles is possible for a sol ageing time lower than 16 days and thatthe size of the mesophase within the thin layer increases with the relative humidity fixed during the film deposition.Finally, an increase of the thermal treatment temperature from 300 to 1000 °C leads to the formation of fluorite-likedioxide material coupled with a loss of nanocrystallites organization and porosity due to the increase of the size of thecrystallites. This loss of nanocrystallites organization is more drastic in the direction perpendicular to the surface andless pronounced along the surface. Thus, a compromise between the crystallization and the preservation of the porosityneeds to be found.

International audience; The preparation and structural characterization of an original Th peroxo sulfate dihydrate, crystallizing at room temperature in the form of stable 1D polymeric microfibres is described. A combination of laboratory and synchrotron techniques allowed solution of the structure of the Th(O2)(SO4)(H2O)2 compound, which crystallizes in a new structure type in the space group Pna21 of the orthorhombic crystal system. Particularly, the peroxide ligand coordinates to the Th cations in an unusual μ3‐η2:η2:η2 bridging mode, forming an infinite 1D chain decorated with sulfato ligands exhibiting simultaneously monodentate and bidentate coordination modes.

Tuning the affinity of a medium for a given metallic cation with the sole modification of weak interactions is a challenge for molecular recognition. Solvent extraction is a key technique employed in the recovery and purification of valuable metals, and it is facing an increased complexity of metal fluxes to deal with. The selectivity of such processes generally relies on the use of specific ligands, designed after their coordination chemistry. In the present study, we illustrate the possibility to employ the sole control of weak interactions to achieve the selective extraction of Pd(II) over Nd(III) : the control over selectivity is obtained by tuning the self-assembly of the organic phase. A model is proposed, after detailed experimental analysis of molecular (XRD, NMR) and supra-molecular (SAXS) features of the organic phases. We thus demonstrate that Pd(II) extraction is driven by metal coordination, whereas Nd(III) extraction requires aggregation of the extractant in addition to metal coordination. These results are of general interest for the applications which rely on the stabilization of metals in organic phases.

International audience; Actinide research at the nanoscale is gaining fundamental interest due to environmental and industrial issues. The knowledge of the local structure and speciation of actinide nanoparticles, which possibly exhibit specific physico-chemical properties in comparison to bulk materials, would help in a better and reliable description of their behaviour and reactivity. Herein, the synthesis and relevant characterization of PuO2 and ThO2 nanoparticles displayed as dispersed colloids, nanopowders or nanostructured oxide powders, allow to establish a clear relationship between the size of the nanocrystals composing these oxides and their corresponding An(IV) local structure investigated by EXAFS spectroscopy. Particularly, the probed An(IV) first oxygen shell evidences an analogous behaviour for both Pu and Th oxides. This observation suggests that the often observed and controversial splitting of the Pu-O shell on the Fourier transformed EXAFS signal of PuO2 samples is attributed to a local structural disorder driven by a nanoparticle surface effect rather than to the presence of PuO2+x species.

This manuscript describes the original structuring of Mg materials under ultrasound irradiation in mild conditions. Golf ball like extended structures can be prepared in dilute oxalic solutions at 20 °C under high frequency ultrasound (200 kHz). An original approach carried out through iterative 3D reconstruction of sonicated surfaces is used to describe surface evolutions and characterize the formed microstructures. A combination of SEM, ICP-AES, contact-angle measurements, and 3D image analyses allows to characterize the roughness and mass loss evolutions, and investigate the mechanism of formation for such architectures. A screening of the sonication experiments clearly points out an ultrasound frequency dependency for the effects generated at the surface. 200 kHz sonication in 0.01 M oxalic acid provides an unprecedented manufacturing of Mg samples which result from a controlled and localized dissolution of the material and characterized by a strong wetting surface with a roughness of 170 nm. The additional formation of newly formed secondary phases appearing with surface dissolution progress is also deciphered. More generally, the ultrasonic procedure used to prepare these engineered surfaces opens new alternatives for the nano- and micro-structuring of metallic materials which may exhibit advanced physical and chemical properties of potential interest for a large community.

International audience; In the last decade organic–inorganic hybrid materials have become essential in materials science as they combine properties of both building blocks. Nowadays the main routes for their synthesis involve electrostatic coupling, covalent grafting, and/or solvent effects. In this field, polyoxometalates (POMs) have emerged as interesting inorganic functional building blocks due to their outstanding properties. In the present work the well‐known α‐Keggin polyoxometalate, α‐PW12O403− (PW), is shown to form hybrid crystalline materials with industrial (neutral) polyethylene glycol oligomers (PEG) under mild conditions, that is, in aqueous medium and at room temperature. The formation of these materials originates from the spontaneous self‐assembly of PW with EOx, (EO=ethylene oxide) with at least four EO units (x>4). The PW–PEG nanoassemblies, made of a POM surrounded by about two PEG oligomers, are stabilized by electrostatic repulsions between the negatively charged PW anions. Addition of NaCl, aimed at screening the inter‐nanoassembly repulsions, induces aggregation and formation of hybrid crystalline materials. Single‐crystal analysis showed a high selectivity of PW towards EO5–EO6 oligomers from PEG200, which is made of a mixture of EO3–8. Therefore, a general “soft” route to produce POM–organic composites is proposed here through the control of electrostatic repulsions between spontaneously formed nanoassemblies in water. However, this rational design of new POM hybrid (crystalline) materials with hydrophilic blocks, using such a simple mixing procedure of the components, requires a deep understanding of the molecular interactions.

The solubilisation of polar and polyphenol antioxidant in vegetable oils was studied. It was shown that the use of a polyglyceryl-3-diisostearate (PG3DS), a bio-sourced emulsifier well known in cosmetics, increases the yield of solubilisation thanks to some aggregation properties analysed using x-ray scattering technique. We show indeed that PG3DS forms reverse aggregates with a critical concentration that depends on the oil polarity. PG3DS reverse aggregates are elongated with a polar core and cannot be really swollen by addition of water. This supramolecular organisation allows however an efficient solubilisation of polar antioxidants in vegetable oils.

A series of bidentate ligands associating an iminophosphorane and a phenoxide were synthesized and coordinated to nickel(II), leading initially to bimetallic KNi adducts. Replacement of the potassium by another metal allowed the isolation and characterization of bimetallic LiNi and AlNi complexes, while addition of one equivalent of triphenylphosphine gave access to monometallic complexes. The same type of complex was obtained with the coordination of a tridentate ligand incorporating a supplementary amine donor. These paramagnetic complexes were characterized by elemental analysis, and some of them by X-ray diffraction, evidencing a tetrahedral nickel center. They were shown to efficiently catalyze the oligomerization of ethylene in the presence of Et2AlCl (Al/Ni = 22.5) with TOF up to 72 000 mol(C2H4)/mol(Ni)/h, giving selectively butene (more than 97%) with at best 93% of 1-C4.

The oxidation of a Ni(II) complex bearing a tetradentate phosphasalen ligand, which differs from salen by the presence of an iminophosphorane (PN) in place of an imine unit, was easily achieved by addition of a silver salt. The site of this oxidation was investigated with a combination of techniques (NMR, EPR, UV/Vis spectroscopy, X-ray diffraction, magnetic measurements) as well as DFT calculations. All data are in agreement with a high-valent Ni(III) center concentrating the spin density. This markedly differs from precedents in the salen series for which oxidation on the metal was only observed at low temperature or in the presence of additional ligands or anions. Therefore, thanks to the good electron-donating properties of the phosphasalen ligand, [Ni(Psalen)](+) represents a rare example of a tetracoordinated high-valent nickel complex in presence of a phenoxide ligand.

We report the synthesis of a unique class of luminescent heterotrinuclear complexes of the general formulas [Pt(terpy)\Cp*Ir-p-(?4-C6H4Se2)\Pt(terpy)][X]4 (X = OTf, 3a; PF6, 3b; BF4, 3c; ClO4, 3d; BPh4, 3e). In these coordination assemblies two Pt(terpy) moieties are held by a stable ?4-diseleno-p-benzoquinone complex [Cp*Ir-p-(?4-C6H4Se2)]. The molecular structures of solvates of 3a and 3b were ascertained by single-crystal X-ray diffraction study and confirmed the formation of the target molecules. The solid-state packing of two of these complexes confirms the presence of π?π and Pt···Pt interactions among individual units providing a 1D supramolecular chain for 3a, while a dimer species is obtained for 3b, illustrating the effect of the counterion on directing the crystal packing of the individual molecules. All compounds show phosphorescence in the red region (685?705 nm) in fluid solution and in the solid state at room temperature, unlike the analogous compound Pt(terpy)\Cp*Ir-p-(?4-C6H4S2)\Pt(terpy)][CF3SO3]4 obtained with a dithiobenzoquinone organometallic linker, which is only luminescent at low temperature.

Stable nucleophilic carbene compounds have recently been shown to be able to mimic in some instances the reactivity of metal fragments in the reaction of unactivated E-H bonds (E = H, R3Si, NH2, R2P). However, the insertion into a B-H bond of the strongly Lewis acidic BH3 molecule has never been observed at a single C atom or even at a metal fragment. Our results show that designed stable, highly electrophilic carbenoid fragments in compounds 4 and 6 can achieve this reactivity in a controlled manner. Density functional theory calculations corroborated the experimental results on the presently designed systems as well as the lack of reactivity on nucleophilic carbenes.

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International audience; Ultrasonically assisted hydrolytic precipitation of U(VI) in the presence of mesoporous alumina followed by thermal treatment of a solid precursor enabled the formation of crystallized uranyl aluminate (URAL) nanoparticles (NPs) dispersed in the alumina matrix. The effect of U(VI) concentration and calcination temperature on the yield of URAL NPs was studied using XRD, XAFS and HRTEM techniques. At 800 °C, URAL NPs (d ≈ 5 nm) are formed only for a low uranium loading of about 5 wt% whereas for a higher content of uranium, larger U3O8 NPs (d ≈ 20 nm) were identified as the principal uranium species. At 500 °C, URAL NPs are formed even for 25 wt% of uranium. The U LIII edge EXAFS spectra pointed out that uranyl cations in URAL are coordinated by bidentate aluminate groups. Presumably URAL is formed during the heating of the 2UO3·NH3·2H2O/AlO(OH) precursor. However, high temperature and higher content of uranium promote transformation of URAL to more thermodynamically stable U3O8. This process is accompanied by the growth of uranium NPs via the Ostwald ripening mechanism.

International audience; A series of highly active yttrium phosphasalen initiators for the heteroselective ring-opening polymerization of rac-lactide are reported. The initiators are yttrium alkoxide complexes ligated by iminophosphorane analogues of the popular "salen" ligand, termed "phosphasalens". A series of novel phosphasalens have been synthesized, with varying substituents on the phenoxide rings and ethylene, propylene, rac-cyclohexylene, R,R-cyclohexylene, phenylene, and 2,2-dimethylpropylene groups linking the iminophosphorane moieties. Changing the substituents on the phosphasalen ligands results in changes to the rates of polymerization (kobs) and to the PLA heterotacticity (Ps = 0.87). Generally, the initiators have high rates, excellent polymerization control, and a tolerance to low loadings.

International audience; The new 1,1′-diphosphaplumbocenes Pb(Dtp)2(Dtp = 2,5-di-tert-butyl-3,4-dimethylphospholyl) and Pb(Dsp)2(Dsp = 2,5-ditrimethylsilyl-3,4-dimethylphospholyl) have beensynthesized and characterized by multinuclear NMR spectroscopy.207Pb NMR spectra of both complexes, as well as for theknown complex Pb(Htp)2 (Htp = 2,5-di-tert-butylphospholyl),show that the phospholyl ligands lead to an important downfieldshift compared with that of cyclopentadienyl based plumbocenes.X-ray diffraction studies of the Pb(Dtp)2 complex revealed astructure with two slightly bent η5-bound ligands. This complexwas employed in the oxidative ligand transfer reaction with bulkydivalent thulium complexes. In the case of Tm(Dtp)2, the firstexample of a monomeric trivalent tris(phospholyl)lanthanidecomplex Tm(Dtp)3 was obtained. X-ray diffraction studies andlow-temperature 1H NMR studies show the η1 coordination mode of the third Dtp ligand. In contrast, oxidation of Tm(Cpttt)2(Cpttt is for tris-tert-butylcyclopentadienyl) led presumably to the formation of the ion pair complex [Tm(Cpttt)2][Dtp], in whichno interaction between the free Dtp ligand and Tm was observed, as shown by variable temperature 1H and 31P NMR studies.The new trivalent complexes could be reduced back to the original divalent complexes with potassium graphite.

Dissolution experiments have been performed in order to determine the solubility constant of coffinite, USiO4. Several assemblages of phases were used in under-saturated experiments performed in 0.1 mol L−1 HCl under Ar atmosphere, as well as in air. These samples were fully-characterized and were composed of either USiO4, solely, or USiO4 and additional oxide byproducts that resulted from the synthesis procedure. The solubility constant of coffinite was determined at 25 °C and 1 bar (log *KS°(USiO4, cr) = −5.25 ± 0.05), as well as the standard free energy of formation of coffinite (ΔfG°(298 K) = −1867.6 ± 3.2 kJ mol−1), which enables one to infer the relative stability of coffinite and uraninite as a function of groundwater composition. Geochemical simulations using PHREEQC 2 software and the Thermochimie data base indicate that coffinite precipitates at 25 °C under reducing conditions, at pH = 6, for H4SiO4(aq) concentration of 7 × 10−5 mol L−1 and U(OH)4(aq) concentration of 10−11 mol L−1. The ΔfG° value determined was used to calculate the standard free energy associated with the formation of coffinite from a mixture of uraninite and quartz. The value obtained (Δr,oxG° = 20.6 ± 5.2 kJ mol−1) indicates unambiguously that coffinite is less stable than the quartz + uraninite mixture at 25 °C. Geochemical simulations using PHREEQC 2 software indicate that coffinite precipitates in solutions supersaturated with respect to UO2(cr), but undersaturated with respect to UO2(am) in aqueous solutions with silica concentrations typical of groundwater. These favorable conditions during the formation of sedimentary uranium ore deposits, as well as slow dissolution kinetics, explain the common occurrence of coffinite.

The reactivity of both the monoanionic and dianionic forms of bis(diphenylthiophosphinoyl)methane (2– and 22–) as well as the dianion of tetraisopropyl methylenediphosphonate(32–) was investigated towards the same CoII precursor CoCl2. Monoanion 2– coordination yields a homoleptic zwitterionic CoII complex. However, both dianions (22– and 32–) give the same overall structure with a square Co2C2 core. Structures of all of the complexes have been confirmed by full NMR spectroscopic analysis and X-ray diffraction. Furthermore, DFT calculations have been carried out to rationalize the stability of such species.

The LiCH2PPh2═NPh derivative 2 was cleanly prepared from the aminophosphonium salt [PhNH−PPh3+][Br−] (1) and MeLi. After formation of the iminophosphorane PPh3═NPh, nucleophilic displacement of one...

Bis(iminophosphoranyl)methanide ({CH(PPh2NR)}−, R = iPr or Ph) neodymium(III) complexes were prepared from NdI3(THF)3.5. The steric bulk of the ligand controlled the stoichiometry of the resulting complexes. Thus, three new complexes, bearing one or two ancillary ligands, were prepared and characterized using various spectroscopic techniques and by single-crystal X-ray diffraction. Reaction of the heteroleptic neodymium iodide complexes with amido groups yielded viable initiators for the ring-opening polymerization of lactide. The polymerizations were conducted using either the heteroleptic neodymium amido complexes or the in situ generated alkoxide complexes. Using such conditions, the neodymium complexes showed very fast and well-controlled polymerizations, with complete conversion being obtained in only a few minutes and yielding polylactide with controlled molecular weight and narrow polydispersity index. An initiating system comprising a rare neodymium-alkyl-carbene complex [Nd{C(PPh2NiPr)2}{CH(PPh2N...

International audience; (Chemical Equation Presented) Two approaches to vinigrol starting from the advanced tricyclic core 7 have been explored using as key intermediates epoxide 12 and diol 17. The preparation of the properly functionalized epoxide 12 has been achieved in a straightforward fashion. However, all attempts to prepare tertiary alcohol 14 by reductive opening of 12 failed. In alternative exploratory efforts to achieve the same goal, allylic alcohols 16 and 29 were prepared by regioselective dehydration of diol 17. Whereas endo-isomer 16 was found to be reluctant to undergo catalytic hydrogenation, the exo counterpart 29 led to the undesired isomer affording after hydrolysis epi-C-8-dihydrovinigrol 32. © 2009 American Chemical Society.

International audience; Chromium(III) complexes bearing R'N(CH2PR2)2 (PCNCP) ligands were prepared. Upon activation with methylaluminoxane, these complexes proved to be effective in the selective tri- and tetramerization of ethylene. The formation of either 1-hexene or 1-octene was found to be highly dependent on the steric bulk of the substituents R on the phosphine moieties. This observation was rationalized using density functional theory calculations on selected steps of the metallacyclic mechanism of the ethylene oligomerization reaction.

Highly reactive: The first divalent organoneodymium complex has been isolated and characterized by X-ray crystallography. It reacts immediately with all common aromatic and ethereal solvents, reduces dinitrogen to form an isolable dinitrogen complex, and undergoes C[BOND]H activation of a ligand tert-butyl group to form a crystallizable "tuck-in" complex (see scheme).

The novel tetradentate ligand 1, associating two phosphines and two iminophosphorane moieties, was easily synthesized from commercially available bis(diphenylphosphino)methane and ethylenediamine via the preparation of the bis(phosphine−aminophosphonium) adduct 1-(HBr)2. Deprotonation of this salt afforded the corresponding tetradentate P2N2 phosphine−iminophosphorane ligand 1. Coordination to Ni(II) and Pd(II) metal centers afforded complexes 2 and 3, respectively, characterized by multinuclear NMR and X-ray analysis. Both cationic complexes adopt a square-planar geometry around the metal, all phosphorus and nitrogen atoms being coordinated. In contrast to most iminophosphorane complexes, 2 and 3 could be handled in water without any apparent decomposition. Their catalytic activity was evaluated in Suzuki−Miyaura coupling. These reactions were conducted in toluene, water, or a biphasic toluene/water medium in the presence of a phase-transfer agent. Under these last conditions, the Pd catalyst 3 (0.1 mol ...

Using a one-pot four-step reaction a readily available phospholide was converted efficiently to a 2-carboxyphosphole. This compound can be used as a building block for the synthesis of phosphole-containing peptides, where the phosphole can serve as a coordination site for late transition metals and may affect the secondary structure of the peptide.

This work highlights the relative importance between structural issues, longer range interactions and solvent effects for a series of ruthenium compounds on their electrochemical and photochemical properties. To study these effects, eight complexes of general formula [Ru(bpy)2(L)]2+ have been synthesized and characterized, where L represents substituted phenyl-imidazophenanthrolines (pip), dipyridophenazines (dppz) and pyrazinophenanthrolines (pzp). This experimental work supported by an important theoretical investigation has pointed out that the electrochemical and the photo-physical behavior of these types of molecular systems depends mainly of the close environment around the photosensitizer. A relation between the ditopic ligand structure (aromatic central part and/or the distal substituents) and the absorption properties have been observed, along with the lower reduction potential of dipyridophenazine and pyrazinophenanthroline moieties. This study points out the influence of the nature of the distal substituents, as well as the significant impact of the solvent nature and the interaction with water molecules, on the photo-physical properties of these ruthenium compounds.

A series of dinuclear [(bpy)2Ru(L)Ru(bpy)2]4+ and mononuclear ruthenium(II) complexes [(bpy)2Ru(L)]2+ where bpy is 2,2′-bipyridine and L represents 2,6-di(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)aryl ligands (DIP) were synthetized and characterized. An original pathway is proposed to obtain mono and hetero bi- and polymetallic Ru complexes and the relation between the molecular structure, the photophysical and electrochemical properties of the single Ru complexes is analysed. The investigated aryl cores are benzene, pyridine and 4-tert-butyl phenol. This work is focused on the effect of the aromatic moiety on the photoinduced charge transfer in the bimetallic compounds and the results are compared with the monometallic analogues. The absence of effect on the UV-visible absorption spectra and on the redox behavior upon varying the nature of the aryl moiety show that the two metallic centres in [(bpy)2Ru(L)Ru(bpy)2]4+ complexes are independent. However, luminescence measurements coupled with DFT calculations highlight a different photophysical behaviour between mono and dinuclear compounds incorporating the benzene core. Theoretical DFT and TD-DFT modelling was used to support the studied physico-chemical properties of these molecular systems.

International audience; The synthesis of the bulky divalent(polyphenylcyclopentadienyl)lanthanoid sandwich complexes[Ln(C5Ph5)2] (Ln = Sm, Eu) and [Ln(C5Ph4H)2(solv)] (Ln =Sm, solv = thf; Ln = Eu, solv = dme)], from redoxtransmetalation/protolysis (RTP) reactions, has beenachieved. An analogous reaction with Yb afforded thesolvent-separated ion pair [Yb(dme)4][C5Ph4H]2. In addition,rare divalent samarium halide complexes [Sm(C5Ph5)(μ-Br)(thf)2]2 and [Sm(C5Ph4H)I(thf)3], were also prepared,either by RTP or ligand rearrangement. X-ray studies showedthat the [Ln(C5Ph5)2] complexes adopt highly symmetrical sandwich structures, whereas the [Ln(C5Ph4H)2(solv)] complexeshave open sandwich structures. The unexpected, but limited, solubility of the [Ln(C5Ph5)2] complexes allowed for variabletemperatureNMR spectra of [Sm(C5Ph5)2] to be obtained. Detailed 1D and 2D NMR studies were conducted on[Sm(C5Ph4H)2(thf)] to ascertain its structure in donor and nondonor solvents. During the course of these studies, the mixedtetraarylcyclopentadienyl sandwich complex [Sm{C5(2,5-Ph)2(3,4-p-tol2)H}2(thf)] was also prepared in order to fully assign thespectrum of [Sm(C5Ph4H)2(thf)]. The europium sandwich complexes [Eu(C5Ph5)2] and [Eu(C5Ph4H)2(dme)] exhibitremarkable luminescence properties with high quantum yields (45% and 41%, respectively) coupled with long emission lifetimes(approximately 800 and 1300 ns, respectively) in toluene.

After internal contamination, uranium rapidly distributes in the body; up to 20 % of the initial dose is retained in the skeleton, where it remains for years. Several studies suggest that uranium has a deleterious effect on the bone cell system, but little is known regarding the mechanisms leading to accumulation of uranium in bone tissue. We have performed synchrotron radiation-based micro-X-ray fluorescence (SR μ-XRF) studies to assess the initial distribution of uranium within cortical and trabecular bones in contaminated rats' femurs at the micrometer scale. This sensitive technique with high spatial resolution is the only method available that can be successfully applied, given the small amount of uranium in bone tissue. Uranium was found preferentially located in calcifying zones in exposed rats and rapidly accumulates in the endosteal and periosteal area of femoral metaphyses, in calcifying cartilage and in recently formed bone tissue along trabecular bone. Furthermore, specific localized areas with high accumulation of uranium were observed in regions identified as micro-vessels and on bone trabeculae. These observations are of high importance in the study of the accumulation of uranium in bone tissue, as the generally proposed passive chemical sorption on the surface of the inorganic part (apatite) of bone tissue cannot account for these results. Our study opens original perspectives in the field of exogenous metal bio-mineralization.

Reaction of 1-bromo-2,5-diphenylphosphole with 10,11-dihydro-5H-dibenzo[b,f]azepine resulted in the formation of the corresponding aminophosphole 3, which was structurally characterized. Reaction of 3 with [Rh2(μ-Cl)2(C2H4)4] and [Rh(COD)2][BF4] afforded the complexes [Rh2(μ-Cl)2(3)2] (4) and [Rh(COD)(3)][BF4] (5), respectively. In both complexes, characterized by NMR as well as by X-ray crystallography, ligand 3 behaves as a chelate through coordination of the phosphorus atom and the olefinic part of the ligand to the rhodium center. The activity of both complexes was tested in the hydroformylation of mono- and disubstituted olefins at 20 bar of CO/H2 pressure. Complex 5 proves to be the most efficient catalyst.

The availability of bis(aminophosphoranes) 2a–c through a straightforward synthesis yielded access to a whole family of N,N ligands via sequential deprotonation. The obtained cationic 3a–c, neutral 4a–c, anionic 5a–c and dianionic 6a–c compounds were fully characterized by NMR and X-ray crystallography. Monocations 3a–c were shown to result from the deprotonation of 2a–c at the bridging methylene carbon. DFT calculations evidenced a substantial negative charge at this carbon. For the neutral bis(iminophosphoranes) 4a–c, two different forms were experimentally observed depending on the nature of the substituent at nitrogen. In the presence of an aryl group, a bis(iminophosphorane) is obtained whereas with alkyl substituent a tautomeric form resulting from a (1,3) hydrogen shift is observed. Theoretical studies were in good agreement with experimental results showing that these two forms are close in energy. The structure obtained for monoanion 5a reveals that a substantial interaction occurs between the anionic carbon and the lithium cation. The X-ray crystal structure of the optically pure dianion 6b has also been recorded.

Four discrete Mn(III)/Mn(II) tetranuclear complexes with a double-cuboidal core, [Mn(4)(hmp)(6)(CH(3)CN)(2)(H(2)O)(4)](ClO(4))(4).2CH(3)CN (1), [Mn(4)(hmp)(6)(H(2)O)(4)](ClO(4))(4).2H(2)O (2), [Mn(4)(hmp)(6)(H(2)O)(2)(NO(3))(2)](ClO(4))(2).4H(2)O (3), and [Mn(4)(hmp)(6)(Hhmp)(2)](ClO(4))(4).2CH(3)CN (4), were synthesized by reaction of Hhmp (2-hydroxymethylpyridine) with Mn(ClO(4))(2).6H(2)O in the presence of tetraethylammonium hydroxide and subsequent addition of NaNO(3) (3) or an excess of Hhmp (4). Direct current (dc) magnetic measurements show that both Mn(2+)-Mn(3+) and Mn(3+)-Mn(3+) magnetic interactions are ferromagnetic in 1-3 leading to an S(T) = 9 ground state for the Mn(4) unit. Furthermore, these complexes are single-molecule magnets (SMMs) clearly showing both thermally activated and ground-state tunneling regimes. Slight changes in the [Mn(4)] core geometry result in an S(T) = 1 ground state in 4. A one-dimensional assembly of [Mn(4)] units, catena-{[Mn(4)(hmp)(6)(N(3))(2)](ClO(4))(2)} (5), was obtained in the same synthetic conditions with the subsequent addition of NaN(3). Double chairlike N(3)(-) bridges connect identical [Mn(4)] units into a chain arrangement. This material behaves as an Ising assembly of S(T) = 9 tetramers weakly antiferromagnetically coupled. Slow relaxation of the magnetization is observed at low temperature for the first time in an antiferromagnetic chain, following an activated behavior with Delta(tau)/k(B) = 47 K and tau(0) = 7 x 10(-)(11) s. The observation of this original thermally activated relaxation process is induced by finite-size effects and in particular by the noncompensation of spins in segments of odd-number units. Generalizing the known theories on the dynamic properties of polydisperse finite segments of antiferromagnetically coupled Ising spins, the theoretical expressions of the characteristic energy gaps Delta(xi) and Delta(tau) were estimated and successfully compared to the experimental values.

A hexanuclear Mn(II) complex [Mn6(Hpao)4(pao)8](ClO4)4 (1) and a nonanuclear mixed-valent Mn complex [Mn9(μ4–O)2(μ3–O)4(CH3CO2)4(pao)8(Hpao)2] · 4H2O (2) have been synthesized from the reaction of simple Mn(II) salts with syn-2-pyridinealdoxime (Hpao) in the presence of base. Structural characterization reveals in both cases the presence of protonated uncoordinated oxime functions, a topology solely held by oxime bridges in 1 and rare Mn(II)–Mn(III)–Mn(IV) mixed-valences in 2. Magnetic studies reveal a spin ground state of S = 0 for complex 1.

Two coordination polymers [MII(H2O)2]2[MoIV(CN)8]·4H2O [MII = Co (1), Mn (2)] were prepared as monocrystals and structurally characterised. These compounds crystallise in the tetragonal systems I4/m (1) and I4/mcm (2) and form three-dimensional networks containing channels occupied by two types of water molecules, i.e. coordinated to MII and crystallised ones. The dehydration of these materials occurs topochemically to give [MII(H2O)]2[MoIV(CN)8] compounds having an open metal coordination site on the MII ions that may be accessible to coordination by other species and serve as a reaction site. The intercalation of water, ammonia and amines has been studied. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

A promising strategy to design highly active catalysts is to use multicomponent catalysts including active metals (such as platinoids) and organosilica as a substrate. In this article, we develop stable OrganoSilica Sandwiches (OSS) consisting of sandwiched metallic layers between organosilica layers. The formation of such a sandwich-like organosilica@platinoid@organosilica material was obtained from bis-silica-alkylammonium carbamate dimers, acting as a template for the immobilization of platinoid salt complexes or metallic nanoparticles in the interlayer space after a reduction treatment. The layered templates and the sandwich structures were investigated by small angle X-ray scattering, coupled thermogravimetric analysis and mass spectrometry, and Raman spectroscopy. It was demonstrated that the meso-structure of the initial template material is not affected by the chemical steps involved in the synthesis of the material and does not depend on the incorporated metal.

International audience; An original copper(I) iodide cluster of novel geometry obtained by using a diphosphine ligand is reported and is formulated [Cu6I6(PPh2(CH2)3PPh2)3] (1). Interestingly, this sort of “eared cubane” cluster based on the [Cu6I6] inorganic core can be viewed as a combination of the two known [Cu4I4] units, namely, the cubane and the open-chair isomeric geometries. The synthesis, structural and photophysical characterisations, as well as theoretical study of this copper iodide along with the derived cubane (3) and open-chair (2) [Cu4I4(PPh3)4] forms, were investigated. A new polymorph of the cubane [Cu4I4(PPh3)4] cluster is indeed presented (3). The structural differences of the clusters were analyzed by solid-state nuclear magnetic resonance spectroscopy. Luminescence properties of the three clusters were studied in detail as a function of the temperature showing reversible luminescence thermochromism for 1 with an intense orange emission at room temperature. This behavior presents different feature compared to the cubane cluster and completely contrasts with the open isomer, which is almost nonemissive at room temperature. Indeed, the thermochromism of 1 differs by a concomitant increase of the two emission bands by lowering the temperature, in contrast to an equilibrium phenomenon for 3. The luminescence properties of 2 are very different by exhibiting only one single band when cooled. To rationalize the different optical properties observed, density functional theory calculations were performed for the three clusters giving straightforward explanation for the different luminescence thermochromism observed, which is attributed to different contributions of the ligands to the molecular orbitals. Comparison of 3 with its [Cu4I4(PPh3)4] cubane polymorphs highlights the sensibility of the emission properties to the cuprophilic interactions.

The functionalization of single-walled carbon nanotubes was performed with four organic molecules. A careful study involving thermo-gravimetric analysis and Raman spectroscopy allowed us to quantify the grafting rate of each molecule, and to evidence a preferential grafting of metallic or semiconducting tube depending on the molecule under consideration. In order to understand the origin of this selectivity, we performed DFT calculations of the electronic structure of the molecules, and compared it to the electron density of states of carbon nanotubes. This approach allowed us to propose a paradigm for explaining the grafting affinity of organic molecules towards metallic or semiconducting nanotubes, and for estimating the grafting efficiency. It could further be used in order to predict the selectivity of any molecule containing a double or triple carbon bond towards metallic or semiconducting carbon nanotubes.

We report a one-step synthesis of the phosphine, PPh(2)(i)C(3)F(7) from commercially available precursors. The stereoelectronic properties of the phosphine were probed by coordination to transition metals. Mo(CO)(5)PPh(2)(i)C(3)F(7) was synthesised and the synthesis and structure of trans-PtCl(2)(PPh(2)(i)C(3)F(7))(2) are described. PPh(2)(i)C(3)F(7) was found to be a bulky electron-withdrawing ligand.

International audience; An in-depth study of mechanochromic and thermochromic luminescent copper iodide clusters exhibiting structural polymorphism is reported and gives new insights into the origin of the mechanochromic luminescence properties. The two different crystalline polymorphs exhibit distinct luminescence properties with one being green emissive and the other one being yellow emissive. Upon mechanical grinding, only one of the polymorphs exhibits great modification of its emission from green to yellow. Interestingly, the photophysical properties of the resulting partially amorphous crushed compound are closed to those of the other yellow polymorph. Comparative structural and optical analyses of the different phases including a solution of clusters permit us to establish a correlation between the Cu-Cu bond distances and the luminescence properties. In addition, the local structure of the [Cu4I4P4] cluster cores has been probed by (31)P and (65)Cu solid-state NMR analysis, which readily indicates that the grinding process modifies the phosphorus and copper atoms environments. The mechanochromic phenomenon is thus explained by the disruption of the crystal packing within intermolecular interactions inducing shortening of the Cu-Cu bond distances in the [Cu4I4] cluster core and eventually modification of the emissive state. These results definitely establish the role of cuprophilic interactions in the mechanochromism of copper iodide clusters. More generally, this study constitutes a step further into the understanding of the mechanism involved in the mechanochromic luminescent properties of metal-based compounds.

International audience; A family of five homobimetallic complexes with magnetically-active trivalent lanthanides of the second half of the series with general formula [{Ln(tta)3}2(μ-bpm)] (Ln = Gd, Tb, Dy, Ho, Er, tta = 2-thenoyltrifluoroacetonato, bpm = 2,2′-bipyrimidine) has been structurally characterized by X-ray diffraction and the magnetic properties of these complexes are reported. The two lanthanide ions are coordinated to the bridging bpm ligand which connects the two metallic centers. The magnetic behavior of these complexes has been investigated. It revealed that a weak antiferromagnetic coupling is observed with the TbIII, DyIII, HoIII, and ErIII ions while a very weak ferromagnetic exchange between the two GdIII ions was observed.

International audience; Early transition metal nucleophilic carbene complexes have been used as stoichiometric carbene transfer agents in a transmetalation process.

International audience; Highly active yttrium phosphasalen initiators for the stereocontrolled ring-opening polymerization of rac-lactide are reported. The initiators are coordinated by a new class of ancillary ligand: an iminophosphorane derivative of the popular "salen" ligand, termed "phosphasalen". Changing the phosphasalen structure enables access to high iso-selectivities (Pi = 0.84) or hetero-selectivities (Ps = 0.87). The initiators also show very high rates, excellent polymerization control, and tolerance to low loadings; furthermore, no chiral auxiliaries/ligands are needed for the stereocontrol. The combination of such high rates with high iso-selectivities is very unusual.

International audience; A new unsymmetrical geminal dianion that contained both a phosphine oxide moiety and a phosphine sulfide moiety has been synthesized. Its reactivity towards Ru(II) was explored, which led to the formation of a highly reactive carbene complex that evolved at room temperature to yield a kinetic orthometalated Ru(II) complex through C-H activation of the phenyl group of the phosphine oxide moiety. This insertion was found to be thermally reversible and a second C-H insertion occurred at a phenyl group of the phosphine sulfide moiety to form the thermodynamic orthometalated Ru(II) complex in a diastereospecific manner. DFT calculations fully rationalized the experimental findings in terms of the relative energies of the kinetic and thermodynamic products and allowed the mechanism of this process to be fully understood.

International audience; Preparation and characterization of three yttrium alkoxide complexes with new phosphasalen ligands are reported. The phosphasalens are analogues of the well-known salen ligands but with iminophosphorane donors replacing the imine function- ality. The three yttrium alkoxide complexes show mono- and dinuclear structures in the solid state, depending on the substituents on the ligand. The new ligands and complexes are characterized using multinuclear NMR spectr oscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction experiments. The complexes are all rapid initiators for lactide polymerization; they show excellent polymerization control on addition of exogeneous alcohol. The mononuclear complex shows extremely rapid rates and a high degree of stereocontrol in rac-lactide polymerization, yielding heterotactic PLA (Psof 0.9). The phosphasalens are, therefore, excellent ligands for lactide ring-opening polymerization catalysis showing superior rates and stereocontrol versus salen ligands, which may be related to their excellent donating ability and the high degrees of steric protection they can confer.

International audience; A copper iodide cluster bearing reactive silanol groups exhibits thermochromic luminescence properties sensitive to its chemical environment and is thus a suitable building block for the synthesis of optically active materials.

International audience; A homobimetallic complex, [{Sm(tta)3(MeOH)}2(μ-bpm)]*1 bpm (tta = 2-thenoyltrifluoroacetonato, bpm = 2,2′-bipyrimidine) has been synthesized and structurally characterized by single-crystal X-ray diffraction. Magnetic measurements (between 5 and 295 K) show that the two metal centers bridged by the bpm connector are magnetically almost isolated. The SmIII emission is observed upon excitation in a wide range of wavelengths going from the UV to the visible (250-500 nm).

International audience; A double ring-expansion methodology allows the stepwise synthesis of tri- and tetra-phosphaporhyrinogens. Structural and calculational methods reveal extended delocalisation about their phospholide centres.

International audience; Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa3̅, and tetragonal I4̅2m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.

Various Ugi—Smiles adducts can be transformed into isoquinolines or isoindoles depending on the conditions.