Michel Ephritikhine

Cea Leti, Grenoble, Rhône-Alpes, France

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Publications (296)847.26 Total impact

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    ABSTRACT: doi: 10.1021/ic500939t
    Inorganic Chemistry 06/2014; · 4.59 Impact Factor
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    ABSTRACT: Polyazines emerge as highly selective ligands toward actinide versus lanthanide separation. Electronic structures of several mono- and polyazine f-complexes of general formula MX3L (M(+3) = Ce, Nd, Eu, U, Am, and Cm; X = RCp(-) or NO3(-); L = N-donor ligand) related to Ln(III)/An(III) differentiation have been investigated using scalar relativistic ZORA/DFT calculations. In all cases, DFT calculations predict shorter An-N bonds than Ln-N ones whatever the azine used, in good agreement with available experimental data. The An-N bonds are also characterized by higher stretching frequencies than Ln-N bonds. The electronic structures of all species have been studied using different population analyses, among them natural population (NPA) and the quantum theory of atoms in molecule approach (QTAIM), as well as using different bond indices. The ability for Ln(III)/An(III) differentiation of the terdentate bipyrazolate BPPR ligand in the M(BPPR)(NO3)3 complexes (M(3+) = Ce, Eu, U and Am ; R = H, 2,2-dimethylpropyl) where BPP = 2,6-bis(dialkyl-1H-pyrazol-3-yl)pyridine has been studied, with a special emphasis on the total metal-ligand bonding energy (TBE). The ZORA/DFT approach was found to properly reproduce the higher selectivity of the polyazine BPP ligand compared to monoazines, especially for the Eu(III)/Am(III) pair operating in spent nuclear fuel, using computed TBEs as criterion. Moreover, the orbital part of the total bonding energy appears also to rationalize well the observed selectivity.
    Inorganic Chemistry 04/2014; · 4.59 Impact Factor
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    ABSTRACT: doi: 10.1021/om500252v
    Organometallics 04/2014; 33(8):2088-2098. · 4.15 Impact Factor
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    ABSTRACT: Condensation of 3-hydroxysalicylaldehyde with 2,4,6-trimethyl-1,3-phenylenediamine gives the ligand N,N′-bis(3-hydroxysalicylidene)-2,4,6-trimethyl-m-phenylenediamine (H4L). The dinuclear zinc(II) complex [Zn(H2L)]2 (1) and the tetranuclear copper(II) square complex [{Cu(H2L)}4(THF)] (2) were synthesized and structurally characterized by single crystal X-ray diffraction. In 1, the ZnII ions are bridged by two H2L molecules and they adopt a tetrahedral geometry. The coordination geometry of the copper atoms in 2 is either square planar or square pyramidal, each metal atom being bound to the NO donor sets of two Schiff base ligands and, in one case, to an extra THF molecule. The arrangement of the tetranuclear complexes in the crystal lattice results in the formation of square channels. Variable temperature magnetic measurements on 2 evidence significant long-range ferromagnetic interactions between the four CuII centres leading to an S = 2 ground state with J1 = +5.81, J2 = +2.36, J3 = +1.73 and J4 = +2.37 cm−1. DFT calculations have been carried out in order to corroborate the experimental fitting and ascertain the origin of this ferromagnetic behaviour.
    New Journal of Chemistry 02/2014; 38(3). · 3.16 Impact Factor
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    ABSTRACT: In stark contrast to uranocene, (Cot)2Th reacts with neutral mono- or bi-dentate Lewis bases to give the bent sandwich complexes (Cot)2Th(L) (L = py, 4,4'-bipy, tBuNC, phen, Me4phen). DFT calculations in the gas phase show that, for both U and Th, formation of the bent compound (Cot)2An(L) should be facile, the linear and bent forms being close in energy.
    Journal of the American Chemical Society 06/2013; · 10.68 Impact Factor
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    ABSTRACT: Reaction of the linear thorocene with NC(-), N3(-) and H(-) led to the bent derivatives [(Cot)2Th(X)](-) (X = CN, N3) and the bimetallic [{(Cot)2Th}2(μ-H)](-), whereas only [(Cot)2U(CN)](-) could be formed from (Cot)2U.
    Chemical Communications 06/2013; · 6.38 Impact Factor
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    ABSTRACT: This method yields imidazole and pyrimidine derivatives from 1,2- and 1,3-diamino substrates.
    ChemInform 06/2013; 44(23).
  • Michel Ephritikhine
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    ABSTRACT: This article gives an overview of the development of uranium carbene complexes. The first example of these compounds was reported in 1981 with the phosphoylide complex Cp3UCHPMe2Ph but nearly three decades passed before the area witnessed spectacular advances. During this time, actinide methylidene compounds were detected in solid argon, carbenoid uranium species were evidenced in McMurry type reactions, and a series of uranium complexes with N-heterocyclic carbene ligands was isolated. The recent developments in uranium carbene chemistry have to be related to the use of bis-phosphorus stabilized geminal carbon dianions as ligands. Homoleptic complexes and a series of mixed chloro-, tetrahydroborato-, amido-, cyclopentadienyl- and cyclooctatetraenyl-carbene complexes of thorium(IV) and uranium in the +4, +5 and +6 oxidation states have been isolated and characterized. DFT calculations led to a good description of the UC double bond that demonstrates a double σ and π donation toward the metal atom with the involvement of the 5f orbitals.RésuméCet article présente une revue sur le développement des complexes carbéniques de l’uranium. Le premier exemple de ces composés apparut en 1981 avec le complexe phosphoylide Cp3UCHPMe2Ph mais ce n’est que presque trente ans plus tard que ce domaine connut de spectaculaires avancées. Entre-temps, des composés méthylidènes des actinides furent détectés dans des matrices d’argon, des espèces carbénoïdes de l’uranium furent mises en évidence au cours de réactions du type McMurry, et une série de complexes de l’uranium comportant des carbènes N-hétérocycliques fut isolée. Les progrès récents dans la chimie des complexes carbéniques de l’uranium doivent être reliés à l’utilisation des dianions géminaux carbonés stabilisés par des groupes phosphorés. Des complexes homoleptiques et une famille de composés carbéniques portant des ligands chlorure, borohydrure, amidure, cyclopentadiényle et cyclooctatetraényle du thorium(IV) et de l’uranium aux degrés d’oxydation +4, +5 et +6 ont été isolés et caractérisés. Les calculs en DFT conduisent à une bonne description de la double liaison UC qui présente une double donation σ et π vers le métal avec l’implication des orbitales 5f.
    Comptes Rendus Chimie. 04/2013; 16(4):391–405.
  • Michel Ephritikhine
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    ABSTRACT: The ubiquity of the cyclopentadienyl ligand permits us to use its complexes as representative examples for the description of recent highlights in organometallic and more generally in coordination chemistry of the actinides. Uranium(III) complexes exhibit a remarkable reactivity, especially in the activation of small molecules, and are valuable precursors of higher valent derivatives. Using redox-active ligands led to the design of reactive complexes which have been considered as “synthons” of AnII and AnIII (An = Th, U). Studies of low-valent compounds gave a better insight into lanthanide(III)/actinide(III) differentiation. Organoactinide(IV) complexes with the bis-Cp* platform play a major role in the synthesis of a variety of compounds containing single and double metal–ligand bonds, revealing novel structures and reactions. The bis(cyclopentadienyl) uranium(IV) and thorium(IV) complexes were also found to be quite efficient in catalytic processes. Cyclopentadienyl complexes afford systems in which actinide ions potentially engage in magnetic exchange interactions. Organoactinide complexes in the +5 and +6 oxidation states remain relatively rare, and most of these are cyclopentadienyl derivatives with oxo and imido ligands.
    Organometallics 03/2013; 32(9):2464–2488. · 4.15 Impact Factor
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    ABSTRACT: The first examples of inorganic nitrite complexes of the natural actinides are described, including the structures of the homoleptic thorium(iv) [PPh(4)](2)[Th(NO(2))(6)] and the uranyl(vi) [PPh(4)](2)[UO(2)(NO(2))(4)] complexes; the nitrite ligand can adopt two different coordination modes in the coordination sphere of the uranyl ion and is unstable towards reduction.
    Chemical Communications 02/2013; 49(24):2412-4. · 6.38 Impact Factor
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    ABSTRACT: Two examples of N-aryloxy-β-diketiminate dianions (11a,b) have been synthesized on a multigram scale, in four steps, from commercially available chemicals. The synthetic scheme relies on the sequential addition of 2,6-diisopropylaniline and 2-amino-4-tert-butylphenol (1a) (or 2-amino-4,6-di-tert-butylphenol (1b)) to acetylacetone, using Et3OBF4 as an activation reagent. Both the nature of the activation reagent and the order of addition of the primary amines have a major impact on the outcome of the reaction, and acid catalysts (such as sulfuric acid or p-toluenesulfonic acid) lead to decomposition of the β-diketiminate backbone via formation of a benzoxazole derivative (3a,b). Using dianions 11a,b, mono- and bis(N-aryloxy-β-diketiminate) complexes of zirconium(IV), ytterbium(III), thorium(IV), and uranium(IV) have been synthesized (12–18), by salt metathesis reactions, and characterized by a combination of 1H/13C NMR spectroscopy, elemental analysis, and X-ray crystallography. The two ligands differ in their steric bulk and exhibit different coordination behaviors, which were rationalized on the basis of geometric considerations.
    Organometallics 01/2013; 32(5):1328–1340. · 4.15 Impact Factor
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    ABSTRACT: Four novel phenyl-end-capped p-conjugated polymers comprising alkyl chains of different lengths were synthesized: the poly(9,9-dihexyl-2,7-fluorene-alt-9,9-dioctylfluorene) (P0), the alternating fluorene– carbazole copolymers P1 and P2 comprising 20% and 50% of carbazole, respectively, and the homopolymer poly(9-hexyl-9H-carbazole) (P3). The non-end-capped alternating fluorene–carbazole copolymer P4 comprising 20% of carbazole was also synthesized for the sake of comparison with P1. P0–P2 and P4 were synthesized by a Pd-catalyzed Suzuki–Miyaura coupling in good yields (80–89%), while P3 was obtained by a Ni-catalyzed Yamamoto coupling reaction from the 3,6-dibromocarbazole monomer in a moderate yield (52%). P0–P4 polymers were characterized by NMR, elemental analysis, and GPC. The molecular weights are 40.30, 23.42, 14.33, 3.92, and 37.49 kDa, with polydispersity indices of 2.5, 1.7, 1.8, 1.3, and 2.6, for P0, P1, P2, P3, and P4, respectively. These polymers were found to show a high thermal stability, with decomposition temperatures in the range of 395–420 C, and the glass transition temperature was found to regularly increase with the amount of carbazole inserted in the conjugated backbone. AFM images obtained on thin films (thickness of about 90 nm) of P0–P2 revealed films with surfaces of good quality, being homogeneous with low roughness (0.2 nm for the smaller ones). These polymers were found to be blue-emitting both in diluted dichloromethane and chlorobenzene solutions as well as in thin films and exhibit relatively high values of the absolute quantum yields in the range of 100–5.5% in dichloromethane and 51.4–7.7% in thin films. Blue-emitting electroluminescent devices were obtained with P0 and P1 as emitting layers, respectively. The device built with P1 showed improved performances (EQE of 1.32%) with respect to the one built with the parent polyfluorene material (EQE of 0.75%).
    Journal of Materials Chemistry 01/2013; · 6.63 Impact Factor
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    ABSTRACT: C 1 , seen them all: A catalytic transformation that uses CO2 as an oxygen‐free C1 building block is presented. The reductive functionalization of CO2 is promoted by N‐heterocyclic carbenes or guanidines as organocatalysts in the presence of amines and hydrosilanes. This diagonal strategy selectively affords benzimidazoles, quinazolinones, 3,4‐dihydroquinazolines, formamidines, and their derivatives, directly from CO2 under mild conditions.
    ChemCatChem 01/2013; 5(1). · 5.18 Impact Factor
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    ABSTRACT: A new class of functionalized β-diketiminate ligands has been prepared from commercially available reagents. The novel N-aryloxy-β-diketiminate ligand proves to be an excellent ligand to support 4d, 4f and 5f metal ions.
    Dalton Transactions 08/2012; 41(39):11980-3. · 4.10 Impact Factor
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    ABSTRACT: The interaction of uranyl nitrate with the series of diamides Et2N(C=O)(CH2)n(C=O)NEt2 (0 ≤ n ≤ 6) was investigated to evaluate systematically the effect of the (CH2)n spacer on the solid-state structures of the corresponding uranyl complexes. Under aerobic conditions, [UO2(NO3)2·6H2O] reacted with an excess amount of these diamides (L) in organic solvents to yield [UO2(κ2-NO3)2(L)] {1 [n = 0, tetraethyloxalamide (TEOA)], 2 [n = 1, tetraethylmalonamide (TEMA)], 3 [n = 2, tetraethylsuccinamide (TESA)], 5 [n = 3, tetraethylglycolamide (TEGA)], 6 [n = 4, tetraethyladipicamide (TEAA)], 7 [n = 5, tetraethylpimelicamide (TEPA)], and 8 [n = 6, tetraethylsubericamide (TESUA)]}, which were isolated and characterized by 1H NMR, ESI-MS, IR, and Raman spectroscopy. Under anhydrous and anaerobic conditions, [UO2(OTf)2] (OTf = trifluoromethanesulfonate) was treated with an excess amount of L to give [UO2(L)2][OTf]2, which was isolated for n = 1 (9) and n = 2 (10). The crystal structures of 2, 5, 6, 7, 8, and of the peroxido-bridged complex [{UO2(κ2-NO3)(L)}2(μ,η2,η2-O2)] (4; n = 2) are presented. In all cases, the uranium ion is eight-coordinated with a classical hexagonal-bipyramidal configuration. The number of CH2 groups in the diamide central chain has considerable influence on the dimensionality of the complexes. They are monometallic (n = 1, 2), dimeric (n = 3, 4), or polymeric (n = 5, 6) with either a helical or zigzag structure, depending on the coordination mode of the bidentate diamide, which can be bridging or not, and the position cis or trans of the nitrate ions. DFT calculations in the gas phase show that the mono- and κ2-bidentate coordination modes of the diamide (1 ≤ n ≤ 5) onto [UO2(κ2-NO3)2] are energetically similar. By using the continuum solvation model, the binding affinity of the κ2-bidentate diamide gradually decreases with the increase in n, but the most stable bidentate uranyl complex is obtained for n = 1 (TEMA). The structural differences in the series of [UO2(κ2-NO3)2{Et2N(C=O)(CH2)n(C=O)NEt2}] complexes are directly related to the length of the (CH2)n spacer.
    European Journal of Inorganic Chemistry 08/2012; 2012(23):3747–3763. · 3.12 Impact Factor
  • Aziz Elkechai, Yamina Mani, Abdou Boucekkine, Michel Ephritikhine
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    ABSTRACT: The redox behavior of tricyclopentadienyl- and phospholyluranium(IV) chloride complexes L(3)UCl with L = C(5)H(5) (Cp), C(5)H(4)Me (MeCp), C(5)H(4)SiMe(3) (TMSCp), C(5)H(4)(t)Bu ((t)BuCp), C(5)Me(5) (Cp*), and C(4)Me(4)P (tmp), has been investigated using relativistic density functional theory calculations, with the solvent being taken into account using the conductor-like screening model. A very good linear correlation (r(2) = 0.99) has been obtained between the computed electron affinities of the L(3)UCl complexes and the experimental half-wave reduction potentials E(1/2) related to the U(IV)/U(III) redox systems. From a computational point of view, our study confirms the crucial importance of spin-orbit coupling and solvent corrections and the use of an extended basis set in order to achieve the best experiment-theory agreement. Considering oxidation of the uranium(IV) complexes, the instability of the uranium(V) derivatives [L(3)UCl](+) is revealed, in agreement with experimental electrochemical findings. The driving roles of both the electron-donating ability of the L ligand and the U 5f orbitals on the redox properties of the complexes are brought to light. Interestingly, we found and explained the excellent correlation between variations of the uranium Hirschfeld charges following U(IV)/U(III) electron capture and E(1/2). In addition, this work allowed one to estimate theoretically the half-wave reduction potential of [Cp*(3)UCl].
    Inorganic Chemistry 06/2012; 51(12):6943-52. · 4.59 Impact Factor
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    ABSTRACT: A highly active organocatalytic system based on N-heterocyclic carbenes has been designed for the formylation of N-H bonds in a large variety of nitrogen molecules and heterocycles, using two chemical wastes: CO(2) and polymethylhydrosiloxane (PMHS).
    Journal of the American Chemical Society 02/2012; 134(6):2934-7. · 10.68 Impact Factor
  • Scott R. Daly, Michel Ephritikhine, Gregory S. Girolami
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    ABSTRACT: The reaction of uranium tetrachloride, UCl4, with sodium N,N-dimethylaminodiboranate, Na(H3BNMe2BH3), in refluxing 1,2-dimethoxyethane (dme) yields small amounts of a new complex, which we formulate as (μ-oxo)hexakis(tetrahydroborato)bis(1,2-dimethoxyethane)diuranium(IV), toluene solvate, U2(μ-O)(BH4)6(dme)2·C7H8, 1. Most likely, the formation of BH4- groups from H3BNMe2BH3- occurs with elimination of [Me2NBH2]2, and formation of the oxo group involves adventitious hydrolysis. Each uranium center in 1 adopts a fac octahedral geometry (counting the BH4 groups as occupying one coordination site); the bridging oxygen atom and the two coordinated oxygen atoms of the dme ligand occupy positions trans to the three BH4- groups. The hydrogen atom positions were located in the electron density difference maps and reveal that all three BH4- groups are bound in a κ3H fashion. The U···B distances to the two BH4- groups that are cis to the bridging oxygen atom are 2.574(6) and 2.584(6) Å, whereas the U···B distances to the BH4- group that is trans to the bridging oxygen of 2.635(7) Å is distinctly longer. Thus, the bridging oxygen atom exerts a noticeable trans influence. The crystallographic and 1H NMR data strongly suggest that the previously reported uranium hydride complex U2(μ-H)2(BH4)6(dme)2 should be reformulated as this oxo complex U2(μ-O)(BH4)6(dme)2.
    Toxicology and Applied Pharmacology - TOXICOL APPL PHARMACOL. 02/2012;
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    ABSTRACT: Magnetic exchange coupling between uranium U(V) ions, in the case of the two para- and meta-imido diuranium complexes, respectively [(C5H5)3U]2(μ-1,4-N2C6H4) and [(C5H5)3U]2(μ-1,3-N2C6H4) exhibiting the 5f1-5f1 configuration, have been investigated using relativistic DFT calculations, combined with the broken symmetry (BS) approach. Using the B3LYP functional, the singlet BS state of the para complex has been found of lower energy than the high spin (HS) triplet one, in agreement with the observed antiferromagnetic character of the complex. On the contrary the BP86 functional fails to predict this magnetic property. The spin density distributions and MO analysis explain well the antiferromagnetic character of the para complex and clarify the failure of the BP86 functional. The effective participation of the 5f metal orbitals in bonding with the imido ligand plays a key role for electronic and magnetic communication between the two active U(V) 5f1 electrons. The same technique led us to explain the ferromagnetic character of the meta isomer in agreement with experiment. For both isomers the spin polarization mechanism explains well their observed magnetic behaviour.
    Comptes Rendus Chimie - C R CHIM. 01/2012;
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    ABSTRACT: In contrast to the neutral macrocycle [UN*(2)(N,C)] (1) [N* = N(SiMe(3))(3); N,C = CH(2)SiMe(2)N(SiMe(3))] which was quite inert toward I(2), the anionic bismetallacycle [NaUN*(N,C)(2)] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me(3)Si)NSiMe(2)CH(2)CH(2)SiMe(2)N(SiMe(3))] resulting from C-C coupling of the two CH(2) groups, and [NaUN*(N,O)(2)] (3) [N,O = OC(═CH(2))SiMe(2)N(SiMe(3))], which is devoid of any U-C bond, was oxidized into the U(V) bismetallacycle [Na{UN*(N,O)(2)}(2)(μ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN(3) or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN*(2)(N,C)(N(3))] [M = Na, 7a or Na(15-crown-5), 7b], M[UN*(2)(N,C)(CN)] [M = NEt(4), 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N(3))(2)] [M = Na, 9a or Na(THF)(4), 9b], [NEt(4)][UN*(N,N)(CN)(2)] (10), M[UN*(N,O)(2)(N(3))] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O)(2)(CN)] [M = NEt(4), 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral U(V) complex [U(N{SiMe(3)}SiMe(2)C{CHI}O)(2)I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined.
    Inorganic Chemistry 11/2011; 50(23):12204-14. · 4.59 Impact Factor

Publication Stats

635 Citations
847.26 Total Impact Points

Institutions

  • 2008–2014
    • Cea Leti
      Grenoble, Rhône-Alpes, France
  • 2009–2012
    • Université Mouloud Mammeri de Tizi Ouzou
      • Faculty of Sciences
      Tizi Ouzou, Wilaya de Tizi Ouzou, Algeria
  • 2001–2010
    • Atomic Energy and Alternative Energies Commission
      Fontenay, Île-de-France, France
  • 2004
    • Tokyo University of Agriculture and Technology
      Edo, Tōkyō, Japan
  • 2000–2004
    • Technion - Israel Institute of Technology
      • Schulich Faculty of Chemistry
      H̱efa, Haifa District, Israel
  • 1980–1984
    • Natural Product Chemistry Institute
      Lutetia Parisorum, Île-de-France, France