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In this work, a series of para-substituted α-phenyl-N-tert-butyl nitrones (PBN) were studied. Their radical-trapping properties were evaluated by electron paramagnetic resonance, with 4-CF3-PBN being the fastest derivative to trap the hydroxymethyl radical (•CH2OH). The redox properties of the nitrones were further investigated by cyclic voltammetry, and 4-CF3-PBN was the easiest to reduce and the hardest to oxidize. This is due to the presence of the electron-withdrawing CF3 group. Very good correlations between the Hammett constants (σp) of the substituents and both spin-trapping rates and redox potentials were observed. These correlations were further supported by computationally determined ionization potentials and atom charge densities. Finally, the neuroprotective effect of these derivatives was studied using two different in vitro models of cell death on primary cortical neurons injured by glutamate exposure or on glial cells exposed to t BuOOH. Trends between the protection afforded by the nitrones and their lipophilicity were observed. 4-CF3-PBN was the most potent agent against t BuOOH-induced oxidative stress on glial cells, while 4-Me2N-PBN showed potency in both models.

International audience; Cyclic voltammetry and spectroelectrochemistry (e.p.r.) were used to investigate the mechanisms implied in the electrocarboxylation of chloroacetonitrile (Cl-CH2-CN, noted RCl) mediated by [Ni(II)(terpy)2]2+. The oxidative addition of chloroacetonitrile on the electrogenerated [Ni(I)(terpy)]+ yields an alkyl-nickel R-Ni(III) complex which is reduced into an alkyl-nickel(II). E.p.r study shows that the homolytic nickel-carbon bond cleavage seems to be the more probable pathway to form the organic radical R-which is reduced to R−. Under carbon dioxide atmosphere, cyclic voltammetry studies show that CO2 was added on the alkyl-Ni(III) complex giving probably a CO2 adduct which is reduced to RCO2-Ni(II) complex allowing to release the carboxylate RCO2− and the active [Ni(I)(terpy)]+ complex. Controlled potential electrolyses showed that good carboxylated and faradic yields were obtained.

Using cyclic voltammetry, differential-pulse voltammetry, and impedance spectroscopy, the electrochemical behavior of a Nafion-1,10-phenanthroline-modified carbon paste electrode (CMCPE: Chemically Modified Carbon Paste Electrode) immersed in a supporting electrolyte 0.1 mol.L-1 acetate buffer solution (pH 4.5) containing iron(II) metal ion was investigated. The optimal analytical parameters for determining iron(II) metal ions (preconcentration potential and time, pH, electrode rotation) have been evaluated and correlated with the surface morphology of the CMCPE surface, the surface chemical composition analysis, and the impedance measurements of the CMCPE immersed in the supporting electrolyte. The experimental impedance values were fitted to an equivalent circuit model using a simple methodology based on a redox polymer-modified electrode. It was shown that among various potentials used for iron(II) accumulation in the Nafion-film, the potential of +1.3 V vs. Ag/AgCl/3 mol. L-1 KCl allowed a better differential-pulse determination of the examined iron(II) metal ion in the supporting electrolyte. With the determination of the iron(II) metal ion in groundwater samples collected in a community on the outskirts of Ouagadougou, the Capital of Burkina Faso, the research was expanded to real applications.

WOS:000489157400025; International audience; In this work, alpha-phenyl-N-tert-butylnitrone (PBN), N-benzylidene-1-diethoxyphosphoryl-1-methylethylamine N-oxide (PPN) and N-benzylidene-1-ethoxycarbonyl-1-methylethylamine N-oxide (EPPN) derivatives bearing methoxy groups (MeO-) on the phenyl ring were synthesized. Their electrochemical properties were studied by cyclic voltammetry and the results showed that the position and the number of methoxy substituents influence the redox potential of the nitronyl group. The spin-trapping ability of the derivatives was next investigated by electron paramagnetic resonance spectroscopy for the hydroxymethyl radical (CH2OH). The ortho, meta and para mono-substituted-PBN derivatives exhibited similar trapping rates to the parent PBN while surprisingly, nitrones with two MeO-substituents on the ortho-position failed to trap CH2OH. The trapping rates of the parent compounds were ranked as follows: PPN \textgreater EPPN \textgreater PBN, indicating that the presence of diethoxyphosphoryl and ethoxycarbonyl electron withdrawing groups on the N-tert-butyl group significantly enhanced the reactivity towards hydroxymethyl radicals. The effect of the substitutions on the atomic partial charges of the nitronyl-moiety and on the ionization potential was computationally rationalized and showed a strong correlation between the ionization potential and the experimentally measured oxidation potential.

International audience; A general synthetic approach to a novel range of semirigid bifunctional chelating agents (BCAs) that include an aromatic ring and a triazolyl moiety in the chelating unit has been investigated for the fac‐[M(CO)3]+ core (M = 185/187Re or 188Re). The strategy includes the facile preparation of these N2O ligands bearing various functionalized arms (carboxylate, terminal alkyne, aromatic amine). The reaction of commercial [Re(CO)5Cl] {or a freshly prepared [Re(OH2)3(CO)3]+ precursor} with our BCAs in methanol led to the formation of stable neutral tricarbonylrhenium complexes of general formula [Re(CO)3(L)] (LH = 5, 10, 11) in high yields. These compounds were characterized by IR and NMR spectroscopy, mass spectrometry, electrochemistry, and X‐ray crystallography for [Re(CO)3(5–H)] and [Re(CO)3(11–H)] as well as by DFT calculations. The analogous rhenium‐188 complexes [188Re(CO)3(5)] and [188Re(CO)3(11–H)] were also prepared, in acceptable to excellent yields, by the reaction of 5 or 11 with the fac‐[188Re(OH2)3(CO)3]+ precursor in methanol at 80 °C. The structural identities of the radioactive complexes were assessed by HPLC studies. The good affinity of these click ligands for the ReI core combined with the ease of their derivatization make this chelating system promising for the conception of target‐specific radiopharmaceuticals for therapeutic purposes.

International audience; Impedance spectroscopy has gained interest for the quantitative detection of specific cells mainly due to a label-free detection and their miniaturization capability required for integration on chip and development of point-of-care diagnostics. In this paper, we report the study of impedimetric microfluidic devices with improved sensitivity targeting the immuno-detection of cells. The sensitivity of our system was evaluated in terms of the capacity of the electrodes to trap monocytes by immune-reaction with CD14 antibody immobilized on micro-electrode surface. All measurements were performed in faradic mode using a redox probe. The sensitivity was evaluated as a function of the impedance increase recorded at 100 Hz caused by the insulating character of the cell trapped on electrodes. Analyses first confirmed that the sensing performances were significantly improved by using microfluidic. This increase could originate from an increase in the probability of cell trapping and a better organization of cells on the electrode due to the laminar flow. The great sensitivity was recorded with interdigitated electrodes for which the influence of the gap value was evaluated. The maximum sensitivity was reached with the smallest inter-electrodes gap tested (50 µm). This performance was in part attributed to the redox cycling taking place between neighboring fingers that was strongly affected when cells were trapped on the electrodes edges. Furthermore we also demonstrate that the slice of cell concentration for which the sensitivity is maximized is correlated to the area of electrodes. Moreover, the smallest area of interdigitated electrode (0.1 mm length) allowed the detection of as low as 5 cells per mL

International audience; Nitrones are known both as therapeutic antioxidants and efficient spin-traps. In this work, the redox behavior of various para-substituted α-phenyl-N-tert-butyl nitrones (PBN) was studied by cyclic voltammetry. The polar effect of the substituents was found to correlate with the electrochemical properties of the nitronyl function. Compounds bearing an electron-withdrawing group were more easily reduced than those having an electron-donating group and an opposite trend was observed for the oxidation. Ease of oxidation was also computationally rationalized using DFT approach showing increased ease of oxidation with electron donating functionalities. Since electrochemical properties of nitrones are known to correlate with biological properties, this work provides insights in the design of potent nitrone antioxidants. Using cyclic voltammetry the relative rate of superoxide trapping by nitrones was investigated and compared to the classical antioxidant BHT. The determination of the relative rate of phenyl radical trapping was also carried out but showed no clear correlation with the nature of the substituents. This indicates the absence of a polar effect in agreement with previous data and further supports the intermediate nature, that is, non- or weakly nucleophile, of phenyl radical. On the contrary kinetics of hydroxymethyl radical trapping was found to correlate with the nature of the substituents, demonstrating the nucleophilic nature of its addition onto nitrones.

International audience; Relevant for engineering a wide range of technological systems, Property Model Methodology (PMM) is applied in this paper to the development process of a helicopter function in the frame of the ARP4754A/ED79A. After a short presentation of the method, the case study is presented: "to retract and to extend airborne the landing gear system". Then, each stage of the PMM development process is illustrated by examples from the case study: (1) Modeling the top level requirements specification, (2) Validating the requirements specification by proof and simulation, (3) Modeling the architectural design, Refining the top level requirements into requirements specified to the different subsystems contributing to the function and Modeling the terminal subsystems detailed designs (4) Validating the requirements specified to the contributing subsystems by proof or simulation, (5) Verifying the design models by simulation and finally (6-8) Verifying physical implementations by test on the basis of all validation and verification scenarios accumulated throughout the development. At end, lessons learnt and industrial perspectives are summarized highlighting how PMM is a methodology adapted to the challenges facing to systems engineering by the globalization of development processes and showing how PMM can provide a powerful conceptual framework to support digital continuity within globalized Design Organizations. Modeling, simulation, proof and test generation activities are supported by the MATLAB and Simulink products. Introduction The aeronautic industry has to deliver more and more complicated systems in term of functions while maintaining high level of quality and safety/reliability. In the same time, competition is driving aircraft manufacturers to strongly improve their costs (including non-recurring costs) and development lead time. At the age of globalization, these systems are designed and produced by large, multicultural, geographically distributed teams belonging to different industrial organizations. This evolution introduces additional complexities (the complexity of a goal-oriented process refers to its propensity to fail [Suh, 2005]). To face these challenges, classical systems engineering approaches

International audience; Guanine radical detection was carried out by a new convenient and efficient method coupling electron paramagnetic resonance spectroscopy and indirect electrooxidation of guanine in different biological environments, from the free nucleotide to several types of DNA substrates. Compared to the widely used photoirradiation method, this method appeared more selective in the choice of the electrochemical mediator. Carried out in presence of a ruthenium mediator and PBN as spin trap, this method revealed two types of EPR spectra depending of the environment of the guanine radical. Both EPR spectra show the trapping of the neutral guanine radical G(−H)• obtained after fast deprotonation of the radical cation G•+. However, they differ by the atom where the trapped radical is centered. This difference highlights the structural dependency of the environment on the nature of the radical formed. This work gave the evidence of an innovative method to detect in situ the guanine radical.

Mechanisms implied in the electrocarboxylation of chloroacetonitrile (Cl–CH 2 –CN, noted RCl) mediated by [Co(II)(phen) 3 ] 2+ have been investigated by cyclic voltammetry and spectroelectrochemistry (UV–Visible and e.p.r.). The studies showed that the oxidative addition of chloroacetonitrile on the electrogenerated [Co(I)(phen) 2 ] + yields an alkyl-cobalt R-Co(III) complex. This complex can either be reduced into an alkyl-cobalt(II) or undergoes a homolytic cobalt–carbon bond cleavage to form the organic radical R and the [Co(II)(phen) 2 ] 2+ complex. Whatever the process, R − and [Co(I)(phen) 2 ] + were produced. In presence of free phenanthroline, the catalytic behaviour of the complex was strongly vanished because the formation of the active complex [Co(I)(phen) 2 ] + is restricted. Under CO 2 atmosphere, the catalytic electrocarboxylation of chloroacetonitrile was observed. Bulk electrolyses showed that the carboxylated and faradic yields depended on the applied electrolysis potential and free phenanthroline concentration.

Graphical abstract, Artemether (AM) plus azithromycin (AZ) rectal co-formulations were studied to provide pre-referral treatment for children with severe febrile illnesses in malaria-endemic areas. The target profile required that such product should be cheap, easy to administer by non-medically qualified persons, rapidly effective against both malaria and bacterial infections. Analytical and pharmacotechnical development, followed by in vitro and in vivo evaluation, were conducted for various AMAZ coformulations. Of the formulations tested, stability was highest for dry solid forms and bioavailability for hard gelatin capsules; AM release from AMAZ rectodispersible tablet was suboptimal due to a modification of its micro-crystalline structure.

International audience; Indolone-N-oxides exert high parasiticidal activity at the nanomolar level in vitro against Plasmodiumfalciparum, the parasite responsible for malaria. The bioreductive character of these molecules was investigated using cyclic voltammetry and EPR spectroelectrochemistry to examine the relationship between electrochemical behavior and antimalarial activity and to understand theirmechanisms of action. For all the compounds (37 compounds) studied, the voltammograms recorded in acetonitrile showed a well-defined and reversible redox couple followed by a second complicated electron transfer. The first reduction (−0.88 VbE1/2b−0.50 V vs. SCE) was attributed to the reduction of the N-oxide function to form a radical nitroxide anion. The second reduction (−1.65 VbE1/2b−1.14 V vs. SCE) was assigned to the reduction of the ketone function. By coupling electrochemistry with EPR spectroscopy, the EPR spectra confirmed the formation of the nitroxide anion radical.Moreover, the experiments demonstrated that a slowprotonation occurs at the carbon of the nitrone function and not at the NO function. A relationship between electrochemical behavior and indolone-N-oxide structure can be established for compounds with R1=―OCH3, R2=H, and electron-withdrawing substituents on the phenyl group at R3. The results help in the design of new molecules with more potent in vivo antimalarial activity.

The electrocarboxylation of chloroacetonitrile (NC–CH2–ClRCl) mediated by [CoIIL2]2+ (L = terpyridine) was investigated by cyclic voltammetry. Electrochemical studies under argon atmosphere showed that the monoelectronic reduction of [CoIIL2]2+ yielded a Cobalt(I) complex which after the loss of a terpyridine ligand reacted with chloroacetonitrile. The oxidative addition of chloroacetonitrile on [CoIL]+ gave an alkylCobalt(III) complex [R–CoIIIL]2+ which was reduced into an alkylCobalt(II) complex, highly unstable and decomposed into an alkyl anion and a Cobalt(II) complex. Under carbon dioxide atmosphere, Cobalt(I) complex was shown to be unreactive towards CO2 but CO2 insertion was observed in the alkylCobalt(III) complex [R–CoIIIL] 2+ giving probably a CO2 adduct [R–CoIIIL(CO2)]2+. This adduct presented a strong adsorption at the carbon electrode and was reduced at potential less cathodic than the one of alkylCobalt(III) complex. After reduction, the carboxylate RCO2− (NC–CH2–CO2−) was released and a catalytic bielectronic carboxylation of chloroacetonitrile took place. Controlled potential electrolyses confirmed the catalytic process and gave for cyanoacetic acid faradic yields up to 60% under low overpotential conditions.

This study describes the grafting of red blood cells (RBC) onto a gold electrode. The erythrocytes were immobilised using antigen/antibody crosslinking based on the bonding of anti-D with the corresponding antigen of the RBC membrane that is shared by all erythrocytes from the positive rhesus group (O + ). To optimise the reproducibility of the modified electrode and to avoid nonspecific interactions, the anti-D layer was deposited onto a protein G layer. The bridge between the protein G and the gold transducer was formed using mixed thiol-based self-assembled monolayer (SAM) (a mixture of 11-mercaptoundecanoic acid and 6-mercapto-1-hexanol in a 1/10 ratio). Each layer deposited was characterized, firstly, with a quartz crystal microbalance to obtain the deposited mass and the corresponding number of moles per square centimetres and secondly, by electrochemical impedance spectroscopy (EIS) using a redox couple Fe(CN) 6 3−/4− (1:1) as an EIS probe. Subsequent modelling with appropriate circuitry enabled the values for each component representing the interface (electrode/film/solution) to be calculated at each step of the grafting process. From these results the surface coverage has been calculated to range from 95 to 98%.

International audience; Today, the price of glycerol has dramatically dropped due to its oversupply from biodiesel production as well as oleochemical industry. Thus, it is essential to develop processes to transform bioglycerol into commercially valued products which is important to ensure sustainability in the biodiesel and oleochemical industries. One possibility is to transform it in propanediols, which have numerous applications such as food additives, raw material in pharmaceutical and cosmetic industries. In this paper, methods of conversion of glycerol into 1,3-propanediol are reviewed and discussed in detail.

The electrochemical behaviour of indoprofen (INP) and its photoproducts was investigated in acetonitrile containing tetrabutylammonium hexafluorophosphate at a Pt or Cv ultramicro-electrodes. These photosensitizers (PS) undergo irreversible oxidation yielding at first a radical cation PS + and more or less reversible reductions through monoelectronic exchange involving a radical anion PS −. By varying the potential scan speed, the stabilities of the radical anions were evaluated. The determination of the redox potential and Rehm–Weller's equation shows the high exergonicity of the oxidative photodamagings whatever is the compound PS. The difference in DNA photosensitizing properties could rather be related to a kinetic control and then to the relative stabilities of the radical anions PS −. Cyclic voltammetry was found powerful in order to get a new insight in the photosensitizing properties of drugs.

Disodium and ditetraphenylphosphonium salts of 2,4-bis(cyanamido)cyclobutane-1,3-dione, Na2(2,4-NCNsq) · 2H2O (1) and (Ph4P)2(2,4-NCNsq) · 4H2O (2) have been synthesized and used to prepare three nickel(II) complexes: [Ni(Him)4(2,4-NCNsq) · 2H2O]n (3), [Ni(Him)3(H2O)(2,4-NCNsq) · H2O]n (4) and [Ni(Him)2(H2O)2(2,4-NCNsq) · 3H2O]n (5). Compounds 1–5 have been synthesized and characterized by electronic absorption and IR spectroscopies and by electrochemical studies. The structures of the salt 2 and of the complexes 3–5 have been determined by X-ray crystallography. The dianion of 2 presents a centro-symmetric square planar structure with two NCN functions deviated from the ring plane by an angle of 20.6°. Complexes 3–5 are polynuclear nickel(II) compounds containing 2,4-NCNsq2− bridging ligands. These ligands are coordinated by the nitrile nitrogen atoms of the cyanamido functions and lie in cis (complex 4) or trans (complexes 3 and 5) positions in the coordination sphere of the nickel(II). The magnetic properties of the three complexes have been investigated in the 2–300 K temperature range (μeff = 2.79–3.34 μB for 3, 2.76–3.25 μB for 4 and 3.14–3.46 μB for 5). Their redox properties are discussed and compared to those of the free 2,4-NCNsq2− dianion.

Three palladium(II) complexes have been synthesized, using 3,4-bis(cyanamido) cyclobutane-1,2-dione dianion (3,4-bis(cyanamido)squarate or 3,4-NCNsq 2− ): [Pd(en)(3,4-NCNsq)] · 1.5H 2 O ( 1 ) (en=1,2-diaminoethane), [Pd(en)(3,4-(NC(O)NH 2 )sq)] · 0.5H 2 O ( 2 ) and K 3 Na[Pd 2 (3,4-(NCN) 2 sq) 4 ] · 5H 2 O ( 3 ). Complex 1 has been characterized by elemental analysis, IR and 13 C NMR spectroscopies. Complexes 2 and 3 have been characterized by single-crystal X-ray diffraction. In complex 2, the unusual hydration of the cyanamido ligand was observed, it proceeds in the coordination sphere of the palladium and leads to a chelating urea squarate ligand. Complex 3 is an anionic dinuclear complex containing four bridging cyanamido squarate ligands. In complexes 2 and 3 , the 3,4-NCNsq 2− ligand (hydrated or not) is, for the first time, coordinated to the metal atom by the two amido nitrogen atoms, either in a chelating mode (complex 2 ) or in a bridging mode giving a short Pd ⋯ Pd distance of 2.8866(15) A (complex 3 ). Electrochemical studies in acetonitrile and dmf solutions have been performed on complexes 1 and 3 .

Three complexes [Ni(Him)4(3,4-NCNsq)(H2O)]·H2O 1, {[Ni2(Him)2(3,4-NCNsq)2(H2O)6]·8H2O}n2 and [Ni(tren)(3,4-NCNsq)]n3, where 3,4-NCNsq2− = 3,4-bis(cyanamido)cyclobutane-1,2-dione dianion and Him = imidazole, have been synthesized and characterized by electronic absorption and IR spectroscopies. The structures of the three complexes have been determined by X-ray crystallography and, for the first time, two conformations of the ligand 3,4-NCNsq2− have been evidenced. Complex 1 consists of mononuclear entities and complexes 2 and 3 are made of infinite chains with nickel(II) atoms bridged by the bis monodentate 3,4-NCNsq2− ions. The magnetic properties of the three complexes have been investigated in the 2–300 K temperature range (μeff = 2.84 to 3.12 μB for 1, μeff = 2.32 to 3.46 μB for 2 and μeff = 2.74 to 3.13 μB for 3). Their redox properties are discussed and compared to those of the free 3,4-NCNsq2− dianion.

Cationic Re(III) complexes [ReX2(PMe3)2(biimH2)]X (where biimH2 = 2,2′-biimidazole; X = Cl, Br, I) are prepared by phosphine displacement in the corresponding PPh3 complexes in the presence of excess PMe3. The N–H protons of co-ordinated biimidazole are moderately acidic and the monodeprotonated form [ReX2(PMe3)2(biimH)] is isolated after addition of one equivalent of NaOCH3. Crystal structures determined for two compounds of each series reveal that strong hydrogen bonding takes place between the N–H groups and the halide counter-ion in the cationic complexes, whereas the neutral molecules crystallise as dimeric units tightly associated via two complementary N–H⋯N interactions. The acidities of the two N–H groups of [ReCl2(PMe3)2(biimH2)]+ in CH2Cl2 are estimated from UV-visible spectra and found to correspond approximately to those of formic acid and 3-chlorophenol, respectively. Electrochemical data on the series of PPh3 and PMe3 complexes with the three halides indicate that the redox potentials of both the metal and the counter-ion are affected by ion pairing in solution.

The crystal structures of two copper(II) complexes of croconate violet (3,5-bis(dicyanomethylene)cyclopentane-1,2,4-trionate=L2−) have been determined by X-ray methods. Complex 1 consists of mononuclear [CuL2(H2O)2]2− ions, potassium cations and two crystallisation water molecules. Complex 2 consists of mononuclear [CuL3]4− ions, (NBu4)+ cations and one half crystallisation water molecule. In these two complexes, the ligand is coordinated in a chelating mode by two adjacent oxygen atoms. The electrochemical behaviour of these complexes is discussed and compared to that of the free croconate violet.

The reaction of copper(II) ions with the 2,4-bis(dicyanomethylene)cyclobutane-1,3-dione dianion (2,4-dcmsq2−), a pseudo-oxocarbon derived from squaric acid in which two carbonyl oxygen atoms have been substituted by dicyanomethylene groups C(CN)2, leads to many complexes according to the preparative scheme. The complex [Cu(2,4-dcmsq)(H2O)4]n has been synthesized and characterized by single-crystal X-ray diffraction. The structure consists of a chain of copper atoms bridged by the ligand with short CuN bonds. Spectroscopic and structural characterizations of the product are compared with those of the previously described [Cu(2,4-dcmsq)(H2O)4·2H2O]n.

Three complexes [Cu2(PPh3)4(MeCN)2(cis-(NCN)2sq)]·MeCN 1, {[Cu2(dien)2(cis-(NCN)2sq)2]·5H2O}n2 and [Cu(tren)(cis-(NCN)2sq)] 3 where [cis-(NCN)2sq]2− = 3,4-bis(cyanamido)cyclobutane-1,2-dione dianion, have been synthesized and characterized by electronic absorption and IR spectroscopies. The structures of the three complexes have been determined by X-ray crystallography. Complex 1 is present as a dinuclear copper(I) compound. Complex 2 is made of infinite chains with copper(II) atoms bridged by the bis monodentate [cis-(NCN)2sq]2− ion. In the mononuclear complex 3 the co-ordination of the cyanamido group unusually occurs via the amido nitrogen and not by the nitrile group; this is accompanied by an important distortion of the co-ordinated cyanamido group. The co-ordination mode of the cyanamido moiety is discussed in regard to IR data and crystallographic results.

The electrocarboxylation of chloroacetonitrile mediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co–C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen). Keywords: Electrocarboxylation, Cobalt tris (phenanthroline), Electrocatalysis, Chloroacetonitrile, Cyanoacetic acid

Mechanical effects induced by ultrasonication can be very helpful for the activation of electrochemical reactions. The continuous cleaning of the electrodes by ultrasound irradiation of the electrochemical cell or the enhancement of mass transfer at the electrodes are examples of such activation. Finally, ultrasonication can play an important part for the orientation of reactions whose selectivities are very sensitive to stirring. Two very different examples have been chosen to illustrate these phenomena: the indirect electrooxidation of di-ketone-L-sorbose into the corresponding ketogulonic acid and the direct electroreduction of acetophenone into pinacol.

The electrochemical behaviour of croconate dianion and dicyanomethylene-substituted croconate dianions was investigated in dimethylformamide containing tetrabutylammonium hexafluorophosphate at a Pt electrode. By cyclic voltammetry, the oxidation of these dianions involves two successive reversible monoelectronic transfers which yield the corresponding radical-anions and neutral species. By reduction of these dianions, the radical-trianions are characterized by uv-vis and esr spectroscopies but are unstable. The redox potentials are strongly dependent on the number of dicyanomethylene groups. Electrochemical kinetics parameters have been determinated. Among the different oxidation states, only the dianions and radical-anions are stable. Due to their high absorption in the uv-visible domain, spectroelectrochemical studies have been carried out to characterize the redox states. The radical-anion/dianion redox couple is sufficiently cyclable for electromodulated colour changes and may be used in electrochromic applications.

The compound (Ph4P)2(trans-cdcb)·2H2O (trans-cdcb2- = 2,4-bis(dicyanomethylene)-cyclobutane-1,3-dione dianion) has been synthesized and characterized by X-ray crystallography. Crystal data: triclinic, space group P1, a = 10.829(2) Å, b = 11.297(2) Å, c = 11.515(2) Å, α = 79.61(1)°, β = 68.54(1)°, γ = 63.49(1)°, V = 1172.9(4) Å3, Z = 1, R = 0.036, Rw = 0.047. With the dianion as a ligand, two complexes have been obtained and characterized by X-ray crystallography, UV-visible spectroscopy, and electrochemistry. The copper(II) complex [Cu(trans-cdcb)(H2O)4·2H2O]n consists of polymeric chains with copper atoms bonded to two of the nitrile groups of the ligand. Crystal data: monoclinic, space group P21/c, a = 9.6366(6) Å, b = 7.1292(3) Å, c = 10.7018(6) Å, β = 99.603(4)°, V = 724.92(7) Å3, Z = 2, R = 0.026, Rw = 0.041. The copper(I) complex[Cu2(trans-cdcb)(CH3CN)4·2CH3CN]n consists of polymeric chains with copper atoms bonded by all the four nitrile groups of the ligand. Crystal data: monoclinic, space group P21/n, a = 10.654(2) Å, b = 8.736(1) Å, c = 14.654(3) Å, β = 109.01(2)°, V = 1291.3(9) Å3, Z = 2, R = 0.037, Rw = 0.041. In CH3CN solution, the copper complexes are dissociated. Moreover, copper(II) is reduced into copper(I) by the dianion. Electrochemistry in the solid state (polymer coated electrode) showed the redox transitions of the different compounds.Key words: pseudo-oxocarbons, X-ray diffraction, copper(II) complex, copper(I) complex, electrochemical behaviour.

International audience; The polynuclear manganese(II) complex of L-dihydroorotic acid has been synthesized and characterized by X-ray crystallography, UV-visible spectroscopy, and magnetic susceptibility measurements. Crystal data: triclinic, space group P1 bar , a = 4.7239(5) , b = 7.902(1) , c = 10.552(2) , = 105.80(1), = 98.864(7), = 104.69(1), V = 355.9(1) D 3, Z = 1, R = 0.035, Rw = 0.028. This complex consists of polymer chains of manganese atoms that are bound together via carboxylate bridges with a Mn . . .Mn distance in the chain of 4.724 D . The radical scavenging properties of the complex have been evaluated by ESR spectroscopy and cyclic voltammetry methods and compared to those of vitamin E and BHT (2,6-di-tert-butyl-4-methylphenol).Key words: orotic acid, L-dihydroorotic acid, manganese(II) complex, antioxidative properties.; Le complexe du manganèse(II) et de l'acide L-dihydroorotique a été synthétisé et caractérisé par spectroscopie UV-visible, susceptibilité magnétique et par diffraction des rayons X. Données cristallographiques : triclinique, groupe d'espace P 1 bar , a = 4.7239(5) D , b = 7.902(1) D , c = 10.552(2) D , α = 105.80(1)°, β = 98.864(7)°, γ~= 104.69(1)°, V = 355.9(1) D 3, Z = 1, R = 0.035, Rw = 0.028. Ce complexe se présente comme une chaine polymérique d'atomes de manganèse liés entre eux par des ponts carboxylate, la distance Mn . . .Mn étant de 4.724 D . Les propriétés antioxydantes de ce composé ont été évaluées par RPE et voltammétrie cyclique et comparées à celles de la vitamine E et du BHT (2,6-di-tert-butyl-4-methylphenol).Mots clés : acide orotique, acide L-dihydroorotique, complexe du manganèse(II), propriétés antioxydantes.

Reaction of copper(II) ion with 3,4-bis(dicyanomethylene)cyclobutane-1,2-dione dianion (cdcb2–) led to a copper(I) complex, [{Cu2(cdcb)(MeCN)2}n]. The crystal structure of this first complex of cdcb has been determined; it consists of layers of Cu2(cdcb)(MeCN)2 units parallel to the ab planes. The redox system of this complex, investigated by electrochemistry and ESR spectroscopy, is formed by the dianion, the radical anion, the neutral species of cdcb and the CuI–CuII system.

The crystal structures of cobalt(II) complexes of croconate [CoL1(H2O)3] 1 (L1 = C5O52–) and croconate violet K2[CoL22(H2O)2]·2H2O 2 [L2 = 3,5-bis(dicyanomethylene)cyclopentane-1,2,4-trionate] have been determined. Complex 1 consists of infinite zig-zag chains constituted by one metal atom, one croconate acting as a bridge and three water molecules. Moreover these chains, parallel to the c axis, are stacked with metal–metal distances of 7.9891(3) A inside a chain and 5.0035(6) A between chains. Complex 2 consists of dianionic and mononuclear entities in which the ligand is O-co-ordinated. The magnetic properties of 1 and 2 have been investigated in the 4–300 K temperature range (µeff = 3.65 to 5.02 µB for 1 and µeff = 4.00 to 4.90 µB for 2). Their redox properties are discussed and compared to those of the free ligands.

The novel trimethylphosphine azido ruthenium(II) complex trans -Ru(N 3 ) 2 (PMe 3 ) 4 has been obtained and characterized by elemental analysis, IR and NMR spectroscopies, and electrochemistry. Its structure has been determined by single crystal X-ray diffraction methods. The complex consists of monomeric Ru(N 3 ) 2 (PMe 3 ) 4 units, in which the coordination geometry around the Ru atom is a distorted octahedron. The two azido ligand occupy trans positions and are oriented in two nearly orthogonal planes. Conversion into the cis isomer in CH 2 Cl 2 has been followed by 31 P NMR and cyclic voltammetry.

The oxidation of diacetone-L-sorbose (DAS) into diacetone-2-keto-L-gulonic acid (DAG) is a step in the synthesis of vitamin C. This oxidation was carried out electrochemically in a stirred cell with the redox couple Ni (OH)2/β-NiOOH as an electrochemical mediator. The anode was made of a current collector (nickel foam or platinized-titanium) and of a suspension of Ni(OH)2 in KOH aqueous media. The mediated electrooxidation of DAS was achieved by the Ni(OH)2β-NiOOH couple in solution which was regenerated at the current collector. This process required a two-compartment reactor but afforded high yields of chemical conversion: we obtained 96% with a 48% faradaic yield. Previous works dealing with DAS electrooxidation to DAG on nickel anode are reviewed hereafter. L'oxydation du diacetone-L-sorbose (DAS) en acide diacetone-2-ceto-L-gulonique (DAG) est une etape importante dans la synthese de la vitamine C. Cette oxydation a ete assistee electrochimiquement par le couple redox Ni(OH)2/β-NiOOH. L'anode etait constituee par un collecteur de courant, soit en mousse de nickel soit en titane platine, et une suspension de Ni(OH)2 en milieu KOH. C'est le β-NiOOH qui assurait l'oxydation du DAS et qui etait regenere a l'anode. Ce procede a necessite un reacteur a deux compartiments mais a conduit a des taux eleves de conversion: nous avons obtenu un rendement chimique de 96% avec un rendement faradique de 48% ont ete obtenus. Nous comparons ici ces resultats avec ceux de la litterature.

International audience; Indolone-N-oxides (INODs) are bioreducible and possess remarkable anti-malarial activities in the low nanomolar range in vitro against different Plasmodium falciparum (P. falciparum) strains and in vivo. INODs have an original mechanism of action: they damage the host cell membrane without affecting non-parasitized erythrocytes. These molecules produce a redox signal which activates SYK tyrosine kinases and induces a hyperphosphorylation of AE1 (band 3, erythrocyte membrane protein). The present work aimed to understand the early stages of the biochemical interactions of these compounds with some erythrocyte components from which the redox signal could originate. The interactions were studied in a biomimetic model and compared with those of chloroquine and artemisinin. The results showed that INODs i) do not enter the coordination sphere of the metal in the heme iron complex as does chloroquine; ii) do not generate iron-dependent radicals as does artemisinin; iii) generate stable free radical adducts after reduction at one electron; iv) cannot trap free radicals after reduction. These results confirm that the bioactivity of INODs does not lie in their spin-trapping properties but rather in their pro-oxidant character. This property may be the initiator of the redox signal which activates SYK tyrosine kinases.

International audience; Effect of copper ions on the electrochemical behaviour of an alkylaminethiol monolayer has been studied by electrochemical impedance spectrosocpy. RAMAN experiment shows the effective adsorption of receptor onto the gold surfaces. The study of Nyquist plot shows that the gold/monolayer/electrolyte interface can be described by a serial combination of two R, CPE electrical circuits. In the presence of increasing amounts of copper, the Nyquist plots at low frequencies were modified showing an increase of the resistance of the second R, CPE electrical circuit. Moreover, this increase of resistance varies linearly with the amounts of copper ions added in solution from 10−8 mol*L−1 to 10−5 mol*L−1.

Croconic acid, H2C5O5, is readily oxidized. This may be attested by decolorization of the solutions and by observation of oxalic acid complexes. The oxidation products are identified by 13C NMR spectroscopy as oxalic and mesoxalic acids, and experimental conditions are specified. The oxidation process requires dioxygen and photons. In parallel, the electrochemical oxidation of croconic acid is studied in aqueous media and in acetonitrile. A potential–pH diagram is drawn. Keywords: croconic acid, oxalic acid, oxidation, electrochemistry, photochemistry.

The electrochemical reduction of μ-oxo bridged Fe III dimers (L)FeOFe(L), where L is a Schiff base, has been investigated in aprotic solvents by cyclic voltammetry and coulometry with UV-vis spectroscopy. Three complexes deriving from Schiff base ligands with N 2 O 2 environments are described. The reduction of (L)Fe III OFe III (L) occurs at a potential around −1 V/SCE and releases the monomeric Fe II (L) complex. A mechanism is proposed using high speed cyclic voltammetry. The reduction pattern is affected by dioxygen through the high reactivity of Fe II (L). These μ-oxo bridged Fe III dimers (L)FeOFe(L) can also be cleaved by Cl − addition and yield the monomeric Fe III (L) complexes. Finally, the FeO bond is not so strong because it cleaves either by electrochemical reduction or by chemical addition of Cl − .

Three complexes of palladium and 3,4-diaminothiophene (L) have been synthesized: [PdL2]Cl2·4H2O (1), PdLCl2(2) and PdLBr2(3). These complexes can be electrochemically oxidized and yield thin-film polymers. One of them, derived from 3, gives a material which can be doped with palladium particles by electroreduction. Crystal data for 1, C8H20Cl2N4O4PdS2, are as follows: M= 441.68, monoclinic, a= 6.6206(2)A, b= 9.8983(1)A, c= 13.2854(1)A, β= 94.47(2)°, V= 868(1)A3, space group P21/c(no. 14), Z= 4, R= 0.0456 and Rw= 0.0677. The ligand is bound to the metal by the amino substituents. The complexes are stacked in parallel columns with short stacking distances (3.27 A).

Graphical abstract, The aim of this study was to identify a candidate formulation for further development of a home or near-home administrable paediatric rectal form of a broad-spectrum antibiotic – specially intended for (emergency) use in tropical rural settings, in particular for children who cannot take medications orally and far from health facilities where injectable treatments can be given. Azithromycin, a broad-spectrum macrolide used orally or intravenously for the treatment of respiratory tract, skin and soft tissue infections, was selected because of its pharmacokinetic and therapeutic properties. Azithromycin in vitro solubility and stability in physiologically relevant conditions were studied. Various pharmaceutical forms, i.e. rectal suspension, two different rectal gels, polyethylene glycol (PEG) suppository and hard gelatin capsule (HGC) were assessed for in vitro dissolution and in vivo bioavailability in the rabbit. Azithromycin PEG suppository appears to be a promising candidate.

The mechanism of electrocrystallization of (cation) x [Ni(dmit)2 (cation = NHMe+ 3, NMe+ 4) conductive compounds is studied under non-stationary conditions by cyclic voltammetry using ultramicroelectrodes at high potential-scan rates. It is shown that the formation of non-integer oxidation state compounds proceeds through one-electron transfers combined with chemical reaction between [Ni(dmit)2 − and [Ni(dmit)2 0 electrogenerated species exhibiting integer charges. The non-integer oxidation state in (cation) x [Ni(dmit)2 compounds (cation = NBu+ 4, AsPh+ 4, NH2Me+ 2, NH3Me+), measured by the non-integer value of x, is determined under stationary conditions by use of the carbon paste electrode at very low potential-scan rates.

Reaction of excess CNCH2SiMe3(L) with CuX2·nH2O (X=NO3−, n=3; ClO4−, n=6) in THF gives the CuI complexes [CuL4]NO3 (1) and [CuL4]ClO4 (2). When CuCN is used as starting material, complex 3, Cu(L3)CN, C4H10O·3H2O, is obtained. Immediate reduction occurs with AgNO3 precipitating metallic Ag. Reactions with MnCl2·6H2O and Mn(NO3)2·6H2O in THF produce two new compounds which analyze as MnL4Cl2·4H2O (6) and MnL2(NO3)2·H2O (7). When excess p-tolylsulfonylmethylisocyanide (L′) is reacted with Cu(NO3)2, the mixed-valence CuICuII complex Cu2L′6(NO3)3 (5) is precipitated, while using CuCN gives the CuI dimer Cu2L′4(CN)2 (4). In analogous conditions the manganese complex MnL′2(NO3)2·C3H6O·3H2O (8) is precipitated. All these complexes have been isolated, characterized by IR, NMR for diamagnetic species, magnetic susceptibilities, EPR measurements and electrochemical analyses. Influence of the two substituents is discussed.

The electron rich cluster Ru[sub 3]([mu][sub 3]-[eta][sup 2]-P(C[sub 6]H[sub 5])(C[sub 5]H[sub 4]N))([mu]-P(C[sub 6]H[sub 5])[sub 2])[sub 3](CO)[sub 6] (9) is prepared by incorporation of diphenylphosphido groups into the ligand shell of triruthenium complexes that already contain a face-bridging phosphido-pyridyl ligand. The two precursors are (i) the known acyl complex Ru[sub 3]([mu]-C(O)(C[sub 6]H[sub 5]))([mu][sub 3]-[eta][sup 2]-P(C[sub 6]H[sub 5])(C[sub 5]H[sub 4]N))(CO)[sub 9] (1), which reacts with 3 equiv of diphenylphosphine in refluxing methylcyclohexane to produce 9 in 75% yield, and (ii) the complex Ru[sub 3]([mu][sub 3]-[eta][sup 2]-P(C[sub 6]H[sub 5])(C[sub 5]H[sub 4]N))([mu]-P(C[sub 6]H[sub 5])[sub 2])(CO)[sub 6]([mu]-CO)[sub 2] (4), which also leads to 9 via reaction with 2 equiv of diphenylphosphine (yield 75%). The structure of compound 9 has been determined by X-ray diffraction. The structure consists of a triangular array of ruthenium atoms capped by a phenylpyridylphosphido ligand as referred to the antecedent species. Each Ru-Ru edge is supported by a diphenylphosphido group occupying equatorial coordination sites. The environment of each Ru atom is completed by two terminal carbonyl ligands. Even though this trinuclear species contains 50 cluster valence electrons, the three Ru-Ru bond distances are equivalent within experimental error. An electrochemical study carried out in CH[sub 2]Cl[sub 2] reveals that the compound undergoesmore » two well-defined reversible one-electron oxidations at E[sub 1/2] = 0.16 V and E[sub 1/2] = 0.53 V, respectively (vs Ag/AgCl, KCl 0.1 M, H[sub 2]O). The unusual closed geometry of 9 is rationalized in terms of molecular orbital calculations of extended Hueckel type and compared with that of the isostructural 48-e closed complex 4 and the isoelectronic 50-e open cluster Ru[sub 2]([mu][sub 3]-[eta][sup 2]-P(C[sub 6]H[sub 5])(C[sub 5]H[sub 4])([mu]-P(C[sub 6]H[sub 5])[sub 2]))(CO)[sub 9] (5). 32 refs., 6 figs., 6 tabs.« less

The electrochemical reduction of Fe III (L)Cl, where L is a Schiff base, has been investigated in aprotic solvents by cyclic voltammetry and coulometry with UV-vis spectroscopy. Six complexes derived from Schiff base ligands with N 2 O 2 environments are described. The reduction of Fe III (L)Cl into Fe II (L)Cl occurs at a potential around −0.5 V vs S.C.E. through an EC mechanism where the following reaction concerns the decomposition of iron(II), a highly reactive complex. A high electronic delocalization of the Schiff base, such as in SALOPH, stabilizes the oxidation state II of iron and shifts the redox potential anodically. The study reveals the extreme reactivity of iron(II) towards dioxygen. Traces of dioxygen with Fe II (L)Cl yield the μ-oxo bridged Fe III dimers (L)FeOFe(L), whose reduction potentials lie around −1 V vs S.C.E. The redox couple Fe II (L)/Fe III (L) is potentially a good electrochemical mediator for redox catalysis.

International audience; The physiological changes caused by external stimuli can be employed as parameters to study pathogen infection in cells and the effect of drugs. Among analytical methods, impedance is potentially useful to give insight into cellular behavior by studying morphological changes, alterations in the physiological state, production of charged or redox species without interfering with in vitro cellular metabolism and labeling. The present work describes the use of electrochemical impedances spectroscopy to simply monitor by modeling impedance plots (Nyquist diagram) in appropriate equivalent circuit, the changes affecting murine macrophage cell line (RAW 264.7) in response to parasite infection by Leishmania amazonensis or to lipopolysaccharide (LPS) treatment. These results demonstrate the ability of electrochemical impedance spectroscopy to discriminate between two opposite cell responses associated to two different stimuli, one caused by the internalization of a parasite, and the other by activation by a bacterium component. Indeed, the study has allowed the characterization, from an electrical point of view, of the extra-cellular NO radical produced endogenously and in great quantities by the inducible form of NO-synthase in the case of LPS-stimulatedmacrophages. This production was not observed in the case of Leishmania-infectedmacrophages for which to survive and multiply, the parasite itself possesses mechanisms which may interfere with NO production. In this latest case, only the intracellular production of ROS was observed. To confirm these interpretations confocal microscopy analysis using the ROS (reactive oxygen species) fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate and electron paramagnetic resonance experiments using Fe(DETC)2 as NO radical spin trap were carried out.

International audience; In this experiment, the concentrations of copper and zinc in brass are obtained by two methods. This experiment does not require advanced instrumentation, uses inexpensive chemicals, and can be easily carried out during a 3-h upper-level undergraduate laboratory. Pedagogically, the basic concepts of analytical chemistry in solutions, such as pH, solubility, complexation, and redox reactions, are illustrated. In addition, this experiment can be used to introduce the science of alloys. Oxidation of brass pieces by concentrated nitric acid yields a solution of Cu2+ and Zn2+ cations. The first method consists in an acid−base titration of Cu2+ and Zn2+ cations by sodium hydroxide. The successive precipitations of the corresponding hydroxide complexes are observed in a pH titration curve that allows the calculation of the concentrations of Cu2+ and Zn2+ and thus the brass composition. The second method is based on complexometric titrations with and without the competition between complexing agents, steps 1 and 2, respectively. In step 1, the copper and zinc together are titrated by EDTA. In step 2, the addition of sodium thiosulfate masks the Cu2+ and the titration by EDTA leads to the determination of Zn2+ concentration. Cu2+ concentration and brass composition are readily obtained.

Squaric (H2Sq) and croconic (H2Croc) acid (H2A) react with [PtL4]2+ (L = ammonia or L2 = ethylenediamine) to yield complexes formulating as [PtL4](HA)2. The crystal structure of the complexes [Pt(en)2](HSq)2 and [Pt(en)2](HCroc)2 have been determined using X-ray diffraction techniques. Oxidation of platinum occurred in the course of the same reaction and complexes of [PtL4Cl2]A were obtained. The X-ray determination of the structure of [Pt(NH3)4Cl2]Sq is reported. Electrochemical measurements have been performed in the solid state to support the results obtained during the oxidation process.

International audience; The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research.

International audience; From the 2,4-bis(cyanamido)cyclobutane-1,3-dione dianion (2,4-NCNsq2−), two copper complexes [Cu2(PPh3)4(PhCN)2(μ-2,4-NCNsq)] · PhCN (1) and [Cu(dien)(μ-2,4-NCNsq) · H2O]n (2) have been synthesized and characterized by IR and electronic absorption spectroscopies. Their structures have been determined by X-ray crystallography. Complex 1 is a dinuclear copper(I) compound with a 2,4-NCNsq2− ligand bridging two copper atoms through the nitrile nitrogen atoms. Complex 2 appears as a 3D network constituted of copper(II) atoms bridged by 2,4-NCNsq2− dianions. This complex presents an unexpected coordination mode of the bis(cyanamido) ligands which are both coordinated via the nitrile functions and via the amido nitrogen atoms of the NCN groups.