On terminal alkynylcarbinols and derivatization thereof

The chemistry of three prototypes of secondary alkynylcarbinols (ACs), recently highlighted as challenging targets in anti-tumoral medicinal chemistry, is further documented by results on n-alkyl, alkynyl and alkenyl representatives. The N-naphthyl carbamate of an n-butyl-AC is thus characterized by X-ray crystallography. A novel dialkynylcarbinol (DAC) with synthetic potential is described, namely the highly dissymmetrical triisopropylsilyl-protected version of diethynylmethanol. The latter is shown to act as a dipolarophile in a selective Huisgen reaction with benzyl azide under CuAAC click conditions, giving an alkenyl-AC, where the alkene unsaturation is embedded in a 1,4-disubstituted 1,2,3-triazole ring, as confirmed by X-ray crystallography.Supplementary information (CIF file

Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

The neutron irradiation-induced structural changes in nuclear grade graphites PCEA and PCIB were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS). The graphite samples were irradiated at the Advanced Test Reactor at the Idaho National Laboratory. Received doses ranged from 1.5 to 6.8 displacements per atom and irradiation temperatures varied between 350 °C and 670 °C. XRD and Raman measurements provided evidence for irradiation induced crystallite fragmentation, with crystallite sizes reduced by 39–55%. Analysis of TEM images was used to quantify fringe length, tortuosity, and relative misorientation of planes, and indicated that neutron irradiation induced basal plane fragmentation and curvature. EELS was used to quantify the proportion of sp2 bonding and specimen density; a slight reduction in planar-sp2 content (due to the buckling basal planes and the introduction of non-six-membered rings) agreed with the observations from TEM

Analyse multiéchellede Carbone pyrolitiques

Pyrocarbons are polyromatic- graphenic- materials obtained by CVD / CVI and are often used as an interphase or as a matrix in C / C composites for the aerospace industry ans the production of brakes, rocket nozzles etc. . . Although not limited to this application domain, this example shows that their mechanical properties and heat resistance are qualities that it is essential to determine and predict. For this purpose, accurate material identification is needed to create a database linking the description of materials to their properties. The work of this thesis is focused on describing the structure (crystallographic point of view), nanotexture (degree of both perfection and order of grapheme layers within anisotropic domains), and texture (extension and relative arrangement of anisotropic domains) of a specific class of these materials, namely laminar pyrocarbons (wich include three kinds of them, known as 'rough', 'smooth' and 'regenerated'). It is mostly based on two major techniques wich are Raman spectroscopy and transmission electron microscopy, completed by X-ray diffraction. The section dedicated to Raman spectroscopy shows a study of the evolution of the various bands characteristic of the material (typically, the G band, generated by the lattice vibrations, and the D band, which is generated by defects) and their respective contributions (areas A or intensities I) as the ID/IG ratio which depends on both the exciting wavelength and the average crystallite size determined by neutron scattering and X-ray diffraction. This work shows that, in particular for small crystallite sizes (< 6 nm), a further contribution to the D band intensity at the same spectral position appears. In comparison to previous works, this innovative approach can account perfectly for the experimental observations recorded for various excitation wave lengths ranging from ultraviolet, to visible, and then to infrared. To complete this study, a series of pitch cokes was studied and shows, consistently with the pyrocarbons, a linear relationship between the width of the G band and the crystallite sizes the latter are less than ˜10nm. The section dedicated to the transmission electron microscopy utilizes a methodology previously developed and validated at CEMES for the quantified multi-scale characterization of another type of pyrocarbons, namely isotropic, spherulitic pyrocarbons has been used for the first time for the characterization of laminar pyrocarbons. By using several modes of the electron microscopy (electron diffraction with selected area diffraction, dark field images, lattice-fringe images), it was possible to evaluate qualitatively and/or quantitatively the structural and nano-textural respectively and to discriminate between the various pyrocarbons studied. This work has also highlighted the limitations of the methodology for its application to the peculiar type of the materials studied.Les Pyrocarbones sont des matériaux polyromatiques -graphéniques- obtenus par CVD/CVI qui sont souvent utilisés en tant qu'interfase ou en tant que matrice dans des composites C/C pour l'industrie aéronautique et la réalisation de freins, tuyères de fusées etc. Bien que non limitées à ce domaine d'application, cet exemple montre que leurs propriétés mécaniques et leur résistance aux températures extrêmes sont des qualités qu'il est primordial de déterminer. Dans ce but, une étape d'identification des matériaux est nécessaire afin de créer une base de données reliant la description des matériaux à leurs propriétés. Le travail de cette thèse s'est donc porté sur la description structurale (caractère cristallographique), nano-texturale (degré de perfection et d'ordre des graphènes au sein des domaines anisotropes) et structurale (étendues et disposition relative des domaines anisotropes) de certains de ces matériaux, les pyrocarbones laminaires (des trois types dits 'rugueux', 'lisses', et 'régénérés'). Il est articulé autour de deux techniques majeures qui sont la spectroscopie Raman et la microscopie électronique en transmission, complété par la diffraction des rayons X. Le volet spectroscopie Raman montre une étude de l'évolution des différentes bandes caractéristiques du matériau (bande G, générée par les vibrations du réseau, et bande D, générée par les défauts) et de leurs importances respectives (aires A ou intensités I), comme le rapport ID/IG, en fonction de la longueur d'onde excitatrice et en fonction de la taille moyenne des cristallites déterminées par diffusion de neutrons et diffraction des rayons X. Ce travail montre notamment que pour de petites tailles de cristallite (< 6nm), une nouvelle contribution à l'intensité de la bande D de même position spectrale apparaît. Cette approche novatrice par rapport aux travaux antérieurs permet de rendre compte parfaitement des observations expérimentales dans le domaine ultraviolet, visible et infrarouge. Afin de compléter cette étude, une série de cokes de brai a été étudiée et montre, en cohérence avec les pyrocarbones, une relation linéaire entre la largeur de la bande G et les tailles de cristallites lorsqu'elles font moins de ˜ 10nm. Dans le volet microscopie électronique en transmission, une méthodologie préalablement mise au point au laboratoire et validée pour la caractérisation multi-échelle quantifiée de pyrocarbones de type pshérulitiques isotropes a été utilisée pour la première fois pour la caractérisation de pyrocarbones laminaires. Pour le recours à plusieurs modes de la microscopie électronique (diffraction électronique à aire sélectionnée, imagerie de fond noir, imagerie de franges de réseau), elle a permis, dans une certaine mesure, d'évaluer qualitativement et/ou quantitativement les caractéristiques texturales et nanotexturales respectives et discriminantes des différents types de pyrocarbones étudiés. Le travail a aussi mis en évidence les limitations de la méthodologie à son application pour le type particulier des matériaux de l'étude

Germylene-β-sulfoxide hemilabile ligand in coordination chemistry

The use of transition-metal germylenes complexes in catalysis remains sporadic, with olny a few recent reports. In this context, we described the synthesis of a germylene-β-sulfoxide ligand and its abilities in coordination chemistry . We characterized transition metal complexes by X-ray diffraction

Two Different Compounds in One Crystal: di-μ-chlorobis[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]diplatinum(II) and chloro(N,N-dimethylformamide-κO)[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]platinum(II)

International audienceThe crystal structures of di-μ-chlorobis[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)] diplatinum(II) (1) and chloro(N,N-dimethylformamide-κO)[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]platinum(II) (2) have been determined by means of the X-ray diffraction. Both complexes cocrystallize in the monoclinic space group C2/c with a = 39.5457(18) Å, b = 7.2482(4) Å, c = 21.2269(10) Å and β = 121.460(2)°. The asymmetric unit consists of half a centrosymmetric compound (complex 1) and one full independent compound (complex 2)

Oxidative additions of alkynyl/vinyl iodides to gold and gold-catalyzed vinylation reactions triggered by the MeDalphos ligand

International audienceThe hemilabile Ad2P(o-C6H4)NMe2 ligand promotes fast, quantitative and irreversible oxidative addition of alkynyl and vinyl iodides to gold. The reaction is general. It works with a broad range of substrates of various electronic bias and steric demand, and proceeds with complete retention of stereochemistry from Z and E vinyl iodides. Both alkynyl and vinyl iodides react faster than aryl iodides. The elementary step is amenable to catalysis. Oxidative addition of vinyl iodides to gold and π-activation of alkenols (and N-alkenyl amines) at gold have been combined to achieve hetero-vinylation reactions. A number of functionalized heterocycles, i.e. tetrahydrofuranes, tetrahydropyranes, oxepanes and pyrrolidines were obtained thereby (24 examples, 87% average yield). Taking advantage of the chemoselectivity for vinyl iodides over aryl iodides, sequential transformations involving first a hetero-vinylation step and then a C–N coupling, a C–C coupling or an heteroarylation were achieved from a vinyl/aryl bis-iodide substrate

N,N′-Bis(4-bromophenyl)-N,N′-dimethylurea

The structure of the title compound, C15H14Br2N2O, at 180 K has monoclinic (P21/n) symmetry. It was obtained unexpectedly from the decomposition of the parent 4-bromo-N-tert-butoxycarbonyl-N-methyl-aniline. It exhibits an `endo' conformation with angles between the two aromatic rings slightly lower than the average values found for similar compounds on the Cambridge Structural Database. In the crystal, C—H...O hydrogen bonds and short Br...Br halogen bonds [3.444 (1) Å] are observed

Strong metal-borane interactions in low-valent cyclopentadienyl Rhodium complexes

International audienceThe first examples of half-sandwich Rh(I) complexes stabilized by borane coordination have been prepared and structurally characterized. As substantiated by NMR spectroscopy and single-crystal x-ray diffraction, the phosphine-borane ligand iPr2P-(o-C6H4)-BFxyl2 1 [Fxyl = 3,5-(F3C)2C6H3] engages in tight eta 3-BCC or eta 1-B coordination, depending on the metal environment

Solid-state and solution characterizations of [(TMPA)Cu(II)(SO3)] and [(TMPA)Cu(II)(S2O3)] complexes: Application to sulfite and thiosulfate fast detection

International audienceSulfite (SO32−) and thiosulfate (S2O32−) ions are used as food preservative and antichlor agent respectively. To detect low levels of such anions we used Cu(II) complex of the Tris-Methyl Pyridine Amine (TMPA) ligand, denoted L. Formation of [LCu(SO3)] (1) and [LCu(S2O3)] (2) in solution were monitored using UV–Vis, EPR and cyclic voltammetry, while the solid-state X-ray structures of both complexes were solved. In addition, we also evaluated the pH range in which the complexes are stable, and the anions binding affinity values for the [LCu(solvent)]2+ (3) parent complex. As a matter of illustration, we determined the sulfite content in a commercial crystal sugar

Spatial confinement model applied to phonons in disordered graphene-based carbons

cited By 1International audienceAnalyzing the various bands in Raman spectra, mostly the G (optical carbon-carbon mode) and D (defect-related double resonance process) bands, is powerful at characterizing defects in disordered graphene-based carbons. The crystallite size La could be estimated from the ID/IG (intensity) or AD/AG (area) ratio, but with large uncertainties. Using the spatial confinement model (SCM) of the phonons has fully explained the linewidth variation for the D band, but could not explain the linewidth variation for the G band over the whole La range. Indeed, if the latter for large, Bernal-stacked graphenes is due to the Kohn anomaly and can be explained considering phonon dispersion curves, turbostratically-stacked graphenes with small La generate an additional broadening of the G band not accounted by the phonon-related SCM only. The realistic SCM proposed here explains the way the G band shape is related to La. The model was also validated by successfully duplicating the evolution of the D (mostly related to the electronic band dispersion) and D′ band linewidths with decreasing La down to 5 nm. The work aims to be a guide for future computational works on Raman spectra of graphene-based carbon materials