Christian Philouze

Publications (47)205.93 Total impact

• Article: Nuclease and anti-proliferative activities of copper(ii) complexes of N3O tripodal ligands involving a sterically hindered phenolate.

  Nathalie Berthet, Véronique Martel-Frachet, Fabien Michel, Christian Philouze, Sylvain Hamman, Xavier Ronot, Fabrice Thomas
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  ABSTRACT: Copper(ii) complexes of a series of tripodal ligands involving a N3O donor set, namely 2-[(bis-pyridin-2-ylmethyl-amino)-methyl]-4-methoxy-phenol (1L), 2-tert-butyl-4-methoxy-6-[bis-pyridin-2-ylmethyl-amino)-methyl]-phenol (2L), 2-tert-butyl-4-methoxy-6-{[(2-pyridin-2-yl-ethyl)-pyridin-2-ylmethyl-amino]-methyl}-phenol (3L), 2-tert-butyl-4-methoxy-6-{[(6-methyl-pyridin-2-ylmethyl)-pyridin-2-ylmethyl-amino]-methyl}-phenol (4L), 2-tert-butyl-4-fluoro-6-{[(6-methyl-pyridin-2-ylmethyl)-pyridin-2-ylmethyl-amino]-methyl}-phenol (5L) and 2-tert-butyl-4-methoxy-6-{bis[(6-methyl-pyridin-2-ylmethyl)-amino]-methyl}-phenol (6L), respectively, were synthesized. Complexes , and were structurally characterized by X-ray diffraction. The structure of is dimeric, with an essentially trigonal bipyramidal geometry around the copper(ii) ions and two bridging deprotonated phenolate moieties. The mononuclear complexes and contain a square pyramidal copper ion, coordinated in axial position by the phenol moiety. In the water-DMF (90 : 10) mixture at pH 7.3 all the copper(ii) complexes are mononuclear, mainly under their phenolate neutral form (except ), with a coordinated solvent molecule. The DNA cleavage activity of the complexes was tested towards the ϕX174 DNA plasmid. In the absence of an exogenous agent does not show any cleavage activity, and are moderately active, while , and exhibit a high nuclease activity. Experiments in the presence of various scavengers reveal that reactive oxygen species (ROS) are not involved in the strand scission mechanism. The cytotoxicity of the complexes was evaluated on bladder cancer cell lines sensitive or resistant to cisplatin. The IC50 values of the complexes , , and are lower than that of cisplatin (range from 6.3 to 3.1 μM against 9.1 μM for cisplatin). Furthermore, complexes , , and are able to circumvent cisplatin cellular resistance.
  Dalton Transactions 04/2013; · 3.84 Impact Factor
• Article: Asymmetric Approach to Hyacinthacines B1 and B2.

  Paidi Venkatram Reddy, Julien Smith, Anushree Kamath, Helene Jamet, Amaël Veyron, Peter Koos, Christian Philouze, Andrew Elliot Greene, Philippe Delair
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  ABSTRACT: Naturally occurring hyacinthacines B1 and B2 have been prepared from a common, easily available, advanced intermediate. The approach features several highly stereoselective transformations: inter alia, a dichloroketene-enol ether [2+2] cycloaddition, a Bruylants alkylation, and an amino-nitrile alkylation-reduction.
  The Journal of Organic Chemistry 04/2013; · 4.45 Impact Factor
• Article: Oxinobactin and Sulfoxinobactin, Abiotic Siderophore Analogues to Enterobactin Involving 8-Hydroxyquinoline Subunits: Thermodynamic and Structural Studies.

  Amaury du Moulinet d'Hardemare, Gisèle Gellon, Christian Philouze, Guy Serratrice
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  ABSTRACT: The synthesis of two new iron chelators built on the tris-l-serine trilactone scaffold of enterobactin and bearing a 8-hydroxyquinoline (oxinobactin) or 8-hydroxyquinoline-5-sulfonate (sulfoxinobactin) unit has been described. The X-ray structure of the ferric oxinobactin has been determined, exhibiting a slightly distorted octahedral environment for Fe(III) and a Δ configuration. The Fe(III) chelating properties have been examined by potentiometric and spectrophotometric titrations in methanol-water 80/20% w/w solvent for oxinobactin and in water for sulfoxinobactin. They reveal the extraordinarily complexing ability (pFe(III) values) of oxinobactin over the p[H] range 2-9, the pFe value at p[H] 7.4 being 32.8. This was supported by spectrophotometric competition showing that oxinobactin removes Fe(III) from ferric enterobactin at p[H] 7.4. In contrast, the Fe(III) affinity of sulfoxinobactin was largely lower as compared to oxinobactin but similar to that of the ligand O-TRENSOX having a TREN backbone. These results are discussed in relation to the predisposition by the trilactone scaffold of the chelating units. Some comparisons are also made with other quinoline-based ligands and hydroxypyridinonate ligand (hopobactin).
  Inorganic Chemistry 11/2012; · 4.60 Impact Factor
• Article: Ligand-Centered Redox Activity in Cobalt(II) and Nickel(II) Bis(phenolate)-Dipyrrin Complexes.

  Amélie Kochem, Linus Chiang, Benoit Baptiste, Christian Philouze, Nicolas Leconte, Olivier Jarjayes, Tim Storr, Fabrice Thomas
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  ABSTRACT: One for all: A trianionic ligand containing the biologically relevant moieties, phenolate and porphyrin, was designed and synthesized. One-electron oxidation of the nickel and cobalt complexes of these ligands affords an unprecedented and highly stable hybrid porphyrinyl-phenoxyl radical bound to the metal center. Two-electron oxidation of these complexes leads to the M(2+) -(close-shell two-electron oxidized ligand) species.
  Chemistry 10/2012; · 5.93 Impact Factor
• Article: Ligand Contributions to the Electronic Structures of the Oxidized Cobalt(II) salen Complexes.

  Amélie Kochem, Hussein Kanso, Benoit Baptiste, Himanshu Arora, Christian Philouze, Olivier Jarjayes, Hervé Vezin, Dominique Luneau, Maylis Orio, Fabrice Thomas
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  ABSTRACT: Square planar cobalt(II) complexes of salen ligands N,N'-bis(3-tert-butyl-5R-salicylidene)-1,2-cyclohexanediamine), where R = OMe (1) and tert-butyl (2), were prepared. 1 and 2 were electrochemically reversibly oxidized into cations [1-H(2)O](+) and [2-H(2)O](+) in CH(2)Cl(2). The chemically generated [1-H(2)O](SbF(6))·0.68 H(2)O·0.82CH(2)Cl(2) and [2-H(2)O](SbF(6))·0.3H(2)O·0.85CH(2)Cl(2) were characterized by X-ray diffraction and NIR spectroscopy. Both complexes are paramagnetic species containing a square pyramidal cobalt ion coordinated at the apical position by an exogenous water molecule. They exhibit remarkable NIR bands at 1220 (7370 M(-1) cm(-1)) and 1060 nm (5560 M(-1) cm(-1)), respectively, assigned to a CT transition. DFT calculations and magnetic measurements confirm the paramagnetic (S = 1) ground spin state of the cations. They show that more than 70% of the total spin density in [1-H(2)O](+) and [2-H(2)O](+) is localized on the metal, the remaining spin density being distributed over the aromatic rings (30% phenoxyl character). In the presence of N-methylimidazole 1 and 2 are irreversibly oxidized by air into the genuine octahedral cobalt(III) bis(phenolate) complexes [1-im(2)](+) and [2-im(2)](+), the former being structurally characterized. Neither [1-im(2)](+) nor [2-im(2)](+) exhibits a NIR feature in its electronic spectrum. 1 and 2 were electrochemically two-electron oxidized into [1](2+) and [2](2+). The cations were identified as Co(III)-phenoxyl species by their characteristic absorption band at ca. 400 nm in the UV-vis spectrum. Coordination of the phenoxyl radical to the cobalt(III) metal ion is evidenced by the EPR signal centered at g = 2.00.
  Inorganic Chemistry 09/2012; 51(20):10557-71. · 4.60 Impact Factor
• Article: Synthesis and X-ray Structure of (2R, 3R, 4R, 5R)-3,4,5-Tris-Benzyloxy-2-Benzyloxymethyl-Piperidin-1-ol, the N-Hydroxy-Analogue of 2,3,4,6-Tetra-O-Benzyl-1-Deoxymannojirimycin

  Emilie Racine, Christian Philouze, Sandrine Py
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  ABSTRACT: AbstractThe title compound 8 was obtained for the first time by hydride-mediated reduction of the d-fructose-derived nitrone 9. The N-hydroxy piperidine 8 is a precursor of the N-hydroxy analogue of DMJ, a potent inhibitor of α-mannosidases. It was isolated as colorless crystals (triclinic, P1 space group) exhibiting the following cell parameters: a=9.947(2)Å; b=12.155(2)Å; c=13.864(5)Å; α=100.98(3)°; β=97.94(2)°; γ=109.50(1)°. The X-ray analysis of a monocrystal of 8 allowed confirmation of its relative configurations and showed the anti orientation of its N-hydroxy group. This structural feature should be useful for considering the interaction of N-hydroxy iminosugars with the recognition site of carbohydrate processing enzymes. Index AbstractThe title compound 8 was prepared for the first time by hydride-mediated reduction of the d-fructose-derived nitrone 9. Compound 8 is a precursor of the N-hydroxy analogue of DMJ, a potent inhibitor of α-mannosidases. The X-ray analysis allowed confirmation of the relative configurations of 8 and showed the anti orientation of its N-hydroxy group. This structural feature will be useful for considering the interaction of N-hydroxy-iminosugars with specific biological targets.
  Journal of Chemical Crystallography 04/2012; 39(7):494-499. · 0.57 Impact Factor
• Article: Geometric and electronic structures of phenoxyl radicals hydrogen bonded to neutral and cationic partners.

  Maylis Orio, Olivier Jarjayes, Benoit Baptiste, Christian Philouze, Carole Duboc, Jenny-Lee Mathias, Laurent Benisvy, Fabrice Thomas
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  ABSTRACT: Two di-tert-butylphenols incorporating an N-methylbenzimidazole moiety in the ortho or para position have been synthesised ((Me)OH and (pMe)OH, respectively). Their X-ray structures evidence a hydrogen bond between the phenolic proton and the iminic nitrogen atom, whose nature is intra- and intermolecular, respectively. The present studies demonstrate that (Me)OH is readily oxidised by an intramolecular PET mechanism to form the hydrogen-bonded phenoxyl-N-methylbenzimidazolium system ((Me)OH)(.+) , whereas oxidation of (pMe)OH occurs by intermolecular PET, affording the neutral phenoxyl benzimidazole ((pMe)O)(.) system. The deprotonations of (Me)OH and (pMe)OH yield the corresponding phenolate species ((Me)O)(-) and ((pMe)O)(-), respectively, whilst that of the previously reported (H)OH (analogous to (Me)OH but lacking the N-methyl group) produces an unprecedented hydrogen-bonded phenol benzimidazolate species, as evidenced by its X-ray structure. The latter is believed to be in equilibrium in solution with its tautomeric phenolate form, as suggested by NMR, electrochemistry and DFT studies. The one-electron oxidations of the anions occur by a simple ET process affording phenoxyl radical species, whose electronic structure has been studied by HF-EPR spectroscopy and DFT calculations. In particular, analysis of the g(1) tensor shows the order 2.0079>2.0072>2.0069>2.0067 for ((Me)O)(.), ((H)O)(.), ((Me)OH)(.+) and ((H)OH)(.+), respectively. ((Me)O)(.) exhibits the largest g(1) tensor (2.0079), consistent with the absence of intramolecular hydrogen bond. The g(1) tensor of ((H)O)(.) is intermediate between those of ((Me)OH)(.+) and ((Me)O)(.) (g(1)=2.0072), indicating that the phenoxyl oxygen is hydrogen-bonded with a neutral benzimidazole partner.
  Chemistry 03/2012; 18(17):5416-29. · 5.93 Impact Factor
• Article: One-electron oxidized copper(II) salophen complexes: phenoxyl versus diiminobenzene radical species.

  Amélie Kochem, Olivier Jarjayes, Benoit Baptiste, Christian Philouze, Hervé Vezin, Kazuaki Tsukidate, Fumito Tani, Maylis Orio, Yuichi Shimazaki, Fabrice Thomas
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  ABSTRACT: Where is the radical? The π-system of the diiminobenzene bridge adds a putative oxidation site to pro-phenoxyl copper(II) salophen complexes. It is shown that the bridge is effectively redox active and that the radical site (phenoxyl vs. diiminobenzene bridge) in the above cations is tuned by selective methoxy substitution.
  Chemistry 12/2011; 18(4):1068-72. · 5.93 Impact Factor
• Source

  Available from: Marius Réglier

  Article: The versatile binding mode of transition-state analogue inhibitors of tyrosinase towards dicopper(II) model complexes: experimental and theoretical investigations.

  Maylis Orio, Constance Bochot, Carole Dubois, Gisèle Gellon, Renaud Hardré, Hélène Jamet, Dominique Luneau, Christian Philouze, Marius Réglier, Guy Serratrice, Catherine Belle
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  ABSTRACT: We describe 2-mercaptopyridine-N-oxide (HSPNO) as a new and efficient competitive inhibitor of mushroom tyrosinase (K(IC) =3.7 μM). Binding studies of HSPNO and 2-hydroxypyridine-N-oxide (HOPNO) on dinuclear copper(II) complexes [Cu(2)(BPMP)(μ-OH)](ClO(4))(2) (1; HBPMP=2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) and [Cu(2)(BPEP)(μ-OH)](ClO(4))(2)) (2; HBPEP=2,6-bis{bis[2-(2-pyridyl)ethyl]aminomethyl}-4-methylphenol), known to be functional models for the tyrosinase diphenolase activity, have been performed. A combination of structural data, spectroscopic studies, and DFT calculations evidenced the adaptable binding mode (bridging versus chelating) of HOPNO in relation to the geometry and chelate size of the dicopper center. For comparison, binding studies of HSPNO and kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone) on dinuclear complexes were performed. A theoretical approach has been developed and validated on HOPNO adducts to compare the binding mode on the model complexes. It has been applied for HSPNO and kojic acid. Although results for HSPNO were in line with those obtained with HOPNO, thus reflecting their chemical similarity, we showed that the bridging mode was the most preferential binding mode for kojic acid on both complexes.
  Chemistry 11/2011; 17(48):13482-94. · 5.93 Impact Factor
• Source

  Available from: Mark E. Casida

  Article: Wavelet-Based Linear-Response Time-Dependent Density-Functional Theory

  Bhaarathi Natarajan, Luigi Genovese, Mark E. Casida, Thierry Deutsch, Olga N. Burchak, Christian Philouze, Maxim Y. Balakirev
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  ABSTRACT: Linear-response time-dependent (TD) density-functional theory (DFT) has been implemented in the pseudopotential wavelet-based electronic structure program BigDFT and results are compared against those obtained with the all-electron Gaussian-type orbital program deMon2k for the calculation of electronic absorption spectra of N2 using the TD local density approximation (LDA). The two programs give comparable excitation energies and absorption spectra once suitably extensive basis sets are used. Convergence of LDA density orbitals and orbital energies to the basis-set limit is significantly faster for BigDFT than for deMon2k. However the number of virtual orbitals used in TD-DFT calculations is a parameter in BigDFT, while all virtual orbitals are included in TD-DFT calculations in deMon2k. As a reality check, we report the x-ray crystal structure and the measured and calculated absorption spectrum (excitation energies and oscillator strengths) of the small organic molecule N-cyclohexyl-2-(4-methoxyphenyl)imidazo[1,2-a]pyridin-3-amine.
  08/2011;
• Article: Radicals of Free and Zinc(II)‐Coordinated α‐Azophenols

  Amélie Kochem, Maylis Orio, Christian Philouze, Hélène Jamet, Amaury du Moulinet d'Hardemare, Fabrice Thomas
  Berichte der deutschen chemischen Gesellschaft 11/2010; 2011(1):45 - 48. · 2.94 Impact Factor
• Article: Co(II), Ni(II), Cu(II) and Zn(II) complexes of a bipyridine bis-phenol conjugate: generation and properties of coordinated radical species.

  Himanshu Arora, Christian Philouze, Olivier Jarjayes, Fabrice Thomas
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  ABSTRACT: Four bis-phenolate complexes [Zn(II)L], [Ni(II)L], [Cu(II)L] and [Co(II)L] (where [H(2)L = 2,2'-[2,2']bipyridinyl-6-yl-bis-4,6-di-tert-butylphenol] have been synthesized. The copper(II) and nickel(II) complexes have been characterized by X-ray diffraction, showing a metal ion within a square planar geometry, slightly distorted towards tetrahedral. The cyclic voltametry (CV) curve of [Zn(II)L] consists of a single bi-electronic reversible wave at 0.06 V vs. Fc/Fc(+). The electrochemically generated dication is a diradical species [Zn(II)L˙˙](2+) that exhibits the typical phenoxyl π-π* band at 395 nm. It is EPR-silent due to magnetic interactions between the phenoxyl moieties. The CV curves of [Ni(II)L] and [Cu(II)L] exhibit two distinct ligand-centred one-electron oxidation waves. The first one is observed at E(1/2)(1) = 0.38 and 0.40 V for the nickel and copper complex, respectively, and corresponds to the formation of M(II)-coordinated phenoxyl radicals. Accordingly, [Ni(II)L˙](+) exhibits a strong absorption band at 960 nm and an (S = ½) EPR signal centred at g(iso) = 2.02. [Cu(II)L˙](+) is EPR-silent, in agreement with a magnetic coupling between the metal and the radical spin. In contrast with the other complexes, [Co(II)L] was found to react with dioxygen (mostly in the presence of pyridine), giving rise to a stable (S = ½) superoxo radical complex [Co(III)L(Py)(O(2)˙)]. One-electron oxidation of [Co(II)L] at -0.01 V affords a diamagnetic cobalt(III) complex [Co(III)L](+) that is inert towards O(2) binding, whereas two-electron oxidation leads to the paramagnetic phenoxyl radical species [Co(III)L˙](+) whose EPR spectrum features an (S = ½) signal at g(iso) = 2.00.
  Dalton Transactions 11/2010; 39(42):10088-98. · 3.84 Impact Factor
• Article: Separation of geometric isomers of a dicopper complex by using a (19)F-labeled ligand: dynamics, structures, and DFT calculations.

  Stéphanie Durot, Laila H Hossain, Sylvain Hamman, Hélène Jamet, Maylis Orio, Isabelle Gautier-Luneau, Dominique Luneau, Christian Philouze, Jean-Louis Pierre, Catherine Belle
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  ABSTRACT: Introducing a fluorine group on two pyridines of the HL(CH(3)) ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) allows the separation of two geometric isomers after complexation by two copper(II) ions. Methods for isolating the isomers (1(meso) and 1(rac)) as a mu-phenoxo,mu-hydroxo dicopper(II) complex as a crystalline product have been developed. Both isomers (1(meso) and 1(rac)) have been characterized by X-ray crystallography and (19)F NMR. The isomerism is determined by the disposition of the fluorine atoms with respect to the plane containing the Cu(2)O(2) core. Density functional theory calculations using different functionals were performed to provide additional support for the existence of these two forms. Dissolution of 1(meso) in acetone or acetonitrile causes its spontaneous isomerization into the 1(rac) form at room temperature. Combined experimental studies (UV-vis, (19)F NMR) and theoretical calculations support this process. Paramagnetic (19)F NMR appears as a unique and powerful probe for distinguishing the two isomers and supplying direct evidence of this isomerization process in solution.
  Inorganic Chemistry 09/2010; 49(17):7832-40. · 4.60 Impact Factor
• Article: Separation of Geometric Isomers of a Dicopper Complex by Using a 19F-Labeled Ligand: Dynamics, Structures, and DFT Calculations

  Stéphanie Durot, Laila H. Hossain, Sylvain Hamman, Hélène Jamet, Maylis Orio, Isabelle Gautier-Luneau, Dominique Luneau, Christian Philouze, Jean-Louis Pierre, Catherine Belle
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  ABSTRACT: Introducing a fluorine group on two pyridines of the HLCH3 ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) allows the separation of two geometric isomers after complexation by two copper(II) ions. Methods for isolating the isomers (1meso and 1rac) as a μ-phenoxo,μ-hydroxo dicopper(II) complex as a crystalline product have been developed. Both isomers (1meso and 1rac) have been characterized by X-ray crystallography and 19F NMR. The isomerism is determined by the disposition of the fluorine atoms with respect to the plane containing the Cu2O2 core. Density functional theory calculations using different functionals were performed to provide additional support for the existence of these two forms. Dissolution of 1meso in acetone or acetonitrile causes its spontaneous isomerization into the 1rac form at room temperature. Combined experimental studies (UV−vis, 19F NMR) and theoretical calculations support this process. Paramagnetic 19F NMR appears as a unique and powerful probe for distinguishing the two isomers and supplying direct evidence of this isomerization process in solution.
  08/2010;
• Article: X-ray structures of copper(II) and nickel(II) radical salen complexes: the preference of galactose oxidase for copper(II).

  Maylis Orio, Olivier Jarjayes, Hussein Kanso, Christian Philouze, Frank Neese, Fabrice Thomas
  Angewandte Chemie International Edition 04/2010; 49(29):4989-92. · 13.45 Impact Factor
• Source

  Available from: Pierre Y Chavant

  Article: MiPNO, a new chiral cyclic nitrone for enantioselective amino acid synthesis: the cycloaddition approach.

  Maryse Thiverny, Christian Philouze, Pierre Yves Chavant, Véronique Blandin
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  ABSTRACT: The resolution of chiral nitrones via derivatization of hydroxylamines was applied to MiPNO, a new, stable, easily prepared chiral cyclic nitrone. The application of MiPNO in totally regio- and diastereo-selective 1,3-dipolar cycloaddition reactions provides an expeditious enantioselective access to unusual gamma-hydroxy alpha-amino acids.
  Organic & Biomolecular Chemistry 02/2010; 8(4):864-72. · 3.70 Impact Factor
• Article: Design and synthesis of a cyclitol-derived scaffold with axial pyridyl appendages and its encapsulation of the silver(I) cation.

  Pierre-Marc Léo, Christophe Morin, Christian Philouze
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  ABSTRACT: Conversion of a myo-inositol derivative into a scyllo-inositol-derived scaffold with C₃(v) symmetry bearing three axial pyridyl appendages is presented. This pre-organized hexadentate ligand allows complexation of silver(I). The crystal structure of the complex was established.
  Beilstein Journal of Organic Chemistry 01/2010; 6:1022-4. · 2.52 Impact Factor
• Article: One-electron oxidized nickel(II) complexes of bis and tetra(salicylidene) phenylenediamine Schiff bases: from monoradical to interacting Ni(III) ions.

  Olaf Rotthaus, Olivier Jarjayes, Christian Philouze, Carlos Pérez Del Valle, Fabrice Thomas
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  ABSTRACT: The nickel(II) complexes of the mono and di-nucleating Schiff base ligands H(2)L(OMe), H(2)L(NO2) and H(4)L(bis) respectively were synthesized and characterized. H(2)L(OMe) and H(2)L(NO2) differ from one another by the substituents of the phenylene spacer, electron-donating methoxy or electron-withdrawing nitro groups respectively. X-Ray crystal structure analysis shows that the nickel(II) ion(s) resides within a square planar geometry in each complex. Cyclic voltammetry curves reveal that the electrochemical communication is strongly influenced by the substituent and the solvent. The one-electron oxidized species [Ni(L(OMe))](+) in CH(2)Cl(2) is a phenoxyl radical with partial delocalization of the spin density on a metal orbital (contribution of 6.8%), whereas [Ni(L(NO2))](+) was found to disproportionate once it is generated. A shift of electronic hole is observed in the presence of pyridine: both [Ni(L(OMe))](+) and the one-electron oxidation product of [Ni(L(NO2))] are converted into mononuclear octahedral nickel(III) complexes involving two axially bound pyridines. In the dinickel(II) complex of H(4)L(bis), namely [Ni(2)(L(bis))], the phenylene spacer mediates an electronic communication between the two metallic sites. Single oxidation of [Ni(2)(L(bis))] affords the delocalized phenoxyl radical [Ni(2)(L(bis))](+), whose EPR signature is close to that of [Ni(L(OMe))](+). Double oxidation affords the bis-{Ni(II)-delocalized radical} species [Ni(2)(L(bis))](2+). Each radical is located at a distinct metallic site and a weak but appreciable magnetic interaction exists between the paramagnetic centres. In the presence of pyridine, a complex involving two ferromagnetically coupled nickel(III) ions is obtained. The magnetic coupling has been estimated to 3.7 cm(-1), while the zero field splitting parameters are |D| = 0.012 cm(-1) and E = 0. They are weak, in agreement with the large intermetallic distance (7.7 A) observed in the neutral precursor [Ni(2)(L(bis))].
  Dalton Transactions 04/2009; · 3.84 Impact Factor
• Article: Galactose oxidase models: insights from 19F NMR spectroscopy.

  Fabien Michel, Sylvain Hamman, Christian Philouze, Carlos Perez Del Valle, Eric Saint-Aman, Fabrice Thomas
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  ABSTRACT: (19)F labelled tripodal ligands that possess a N(3)O donor set (one phenol, one tertiary amine and either two pyridines or one pyridine and one quinoline) have been synthesized. The fluorine is incorporated either at the phenol O-donor (HL(F) and HL(CF3)) or at the quinoline N-donor (HLq(OMe) and HLq(NO2)). The copper(ii)-phenol complexes (2H)(2+), (1H)(2+), (3H)(2+) and (4H)(2+) as well as the corresponding copper(ii)-phenolate complexes have been characterized. X-Ray diffraction reveals an increase in the oxygen-copper bond distance of more than 0.4 A upon protonation of the phenolate moiety of (4)(+). Protonation is accompanied by an axial to equatorial isomerization of the quinoline group. DFT calculations show that stretching of the Cu-O(phenol) bond, pi-stacking interactions and rotation of the pyridine are key steps in this isomerization process. Protonation, and thus changes in the oxygen-copper bond distance induce either a decrease ((1H)(2+), (2H)(2+)) or an increase ((3H)(2+) and (4H)(2+)) in the copper-fluorine distance that could be monitored by (19)F NMR. In the former case, a broadening of the (19)F NMR signal is observed, whereas a sharpening is observed in the latter case. Temperature dependent (19)F NMR measurements on equimolar mixtures of the phenol and phenolate complexes of (3)(+) and (4)(+) reveal rate constants for proton transfer and/or isomerization of 3000 +/- 100 s(-1) and 2900 +/- 100 s(-1), respectively, at the coalescence temperature. This temperature was found to be strongly affected by the phenol para-substituent as it is 226 K and ca. 330 K for (3)(+) and (4)(+), respectively. A phenoxyl radical species ((3 )(2+)) could be generated and characterized for the first time by (19)F NMR spectroscopy.
  Dalton Transactions 03/2009; · 3.84 Impact Factor
• Article: An unusual stable mononuclear Mn(III) bis-terpyridine complex exhibiting Jahn-Teller compression: electrochemical synthesis, physical characterisation and theoretical study.

  Sophie Romain, Carole Duboc, Frank Neese, Eric Rivière, Lyall R Hanton, Allan G Blackman, Christian Philouze, Jean-Claude Leprêtre, Alain Deronzier, Marie-Noëlle Collomb
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  ABSTRACT: The mononuclear manganese bis-terpyridine complex [Mn(tolyl-terpy)(2)](X)(3) (1(X)(3); X=BF(4), ClO(4), PF(6); tolyl-terpy=4'-(4-methylphenyl)-2,2':6',2"-terpyridine), containing Mn in the unusual +III oxidation state, has been isolated and characterised. The 1(3+) ion is a rare example of a mononuclear Mn(III) complex stabilised solely by neutral N ligands. Complex 1(3+) is obtained by electrochemical oxidation of the corresponding Mn(II) compound 1(2+) in anhydrous acetonitrile. Under these conditions the cyclic voltammogram of 1(2+) exhibits not only the well-known Mn(II)/Mn(III) oxidation at E(1/2)=+0.91 V versus Ag/Ag(+) (+1.21 V vs. SCE) but also a second metal-based oxidation process corresponding to Mn(III)/Mn(IV) at E(1/2)=+1.63 V (+1.93 V vs. SCE). Single crystals of 1(PF(6))(3)2 CH(3)CN were obtained by an electrocrystallisation procedure. X-ray analysis unambiguously revealed its tetragonally compressed octahedral geometry and high-spin character. The electronic properties of 1(3+) were investigated in detail by magnetic measurements and theoretical calculations, from which a D value of +4.82 cm(-1) was precisely determined. Density functional and complete active space self consistent field ab initio calculations both correctly predict a positive sign of D, in agreement with the compressed tetragonal distortion observed in the X-ray structure of 1(PF(6))(3)2 CH(3)CN. The different contributions to D were calculated, and the results show that 1) the spin-orbit coupling part (+2.593 cm(-1)) is predominant compared to the spin-spin interaction (+1.075 cm(-1)) and 2) the excited triplet states make the dominant contribution to the total D value.
  Chemistry 01/2009; 15(4):980-8. · 5.93 Impact Factor