Synthesis of a new bowl-shaped polyarene aiming

Efficient hydrogen storage is one of the major hurdles towards a potential hydrogen economy. Curved molecules are very interesting for this purpose because of their permanent electrical dipole moment, which can induce a dipole moment on H2 molecules increasing therefore the dipole-dipole interaction and so their adsorption. This work presents the synthesis of a new bowl-shaped polyarene based on curved corannulene’s motive. Since corannulene is known for its ability to adsorb hydrogen, the greater surface and curvature of our target molecule is assumed to increase the hydrogen adsorption. The plan was to start from phenanthrene-9,10-dione and 1-phenylpropan-2-one to obtain a planar polycyclic aromatic hydrocarbon (PAH) containing a five-membered ring. Then, via a crosscoupling reaction and a classical Scholl reaction under Kovacic conditions, it would have been possible to obtain the bowl-shaped molecule. Unfortunately, the synthesis of the first precursor presented obstacles and, from three proposed strategies, only one allowed the obtainment of the planar PAH in acceptable yield. Moreover, only one attempt for the coupling reaction was made and, because of the small amount and the impurity of the obtained product, no Scholl reaction was performed. Therefore, the desired bowl-shaped polyaromatic compound has not been obtained and the efficacy of the Scholl reaction for this synthesis has not been tested

Hexa-peri-hexabenzocoronenes – Controlling their Self-Assembly by Engineering the Lateral Substituents

Polycondensed aromatic hydrocarbons (PAH), which can be regarded as two-dimensional subsections of graphite, have begun to attract increasing interest in supramolecular chemistry. Substituted hexa-peri-hexabenzocoronenes (HBC), an outstanding class of PAH, are well-known to self-organize in solution into highly ordered columnar molecular stacks. The formed structures are very sensitive to any variation of the medium as well as the lateral substituents of the HBC derivatives. Various perfluoroalkylated HBC compounds have been prepared and investigated by powder XRD, DSC, fluorescence and cryo-SEM in order to gain certain control over the self-assembling behavior of this class of compounds

Reactivity of Allenes towards Iron Carbonyl Complexes

A series of monosubstituted allenes was reacted with Fe2(CO)9 to give dinuclear iron-carbonyl complexes containing organic ligands derived either from monomeric or dimerized allene. A mechanism of formation is proposed based on isolated intermediates. These intermediates point to an allene dimerization via addition of a reactive allene iron complex to free allene. Unusual chemical shifts were observed for many resonances in the 1H- and 13C-NMR spectra of the new compounds

Synthesis of perfluoroalkylated bulky triarylamines

The synthesis of two new triarylamine compounds bearing perfluoroalkylated side chains is described. Good thermal stabilities combined with a blue emission make these compounds promising candidates for materials applications

Novel iron tweezers complexes for hydrogenation and polymerization of olefins

L’utilisation des complexes organométalliques comme catalyseurs est devenu un domaine très important de la chimie des matériaux. Cependant et malgré ce développement, les catalyseurs à base de fer(II) sont peu employés dans la polymérisation d’oléfines. Un de rares catalyseur utilisé dans ce contexte est le complexe tridenté diimine pyridine développé par Gibson et Brookhart. Cependant ce modèle souffre par son manque de tolérance envers le moindre changement effectué dans son enveloppe, résultant par une diminution drastique de son activité catalytique. Le but de ce travail est de synthétiser des catalyseurs de fer(II) contenant des ligands chelates et d’étudier leur utilisation dans la polymérisation d’oléfines. Il est important de signaler que des travaux précédents dans notre groupe on montré une très bonne corrélation entre la polymérisation et l’hydrogénation d’oléfines. Ainsi nous avons aussi exploité l’habilité de nos complexes dans l’hydrogénation. Deux projets ont été menés en parallèle : il s’agit de la synthèse de complexes de fer(II) contenant d’un côté le ligand benzylétherfurane et de l’autre côté les ligands carbenes bisimidazol-2-ylidene. Le complexe de fer(II) benzyletherfurane a été employé avec succès dans l’hydrogénation d’oléfines sous des conditions très douces (1-3 bar d’hydrogène et à température ambiante), cependant son emploi comme catalyseur de polymérisation d’oléfines n’a pas donné les résultats escomptés. Compte tenu de ceci, ce projet à été mis à côté au profit des complexes de fer(II) bisimidazol-2-ylidene qui eux ont montré une bonne activité dans les deux réactions, polymérisation et hydrogénation des oléfines sous des conditions douces. Durant la préparation de ces précatalyseurs, plusieurs autres complexes de fer(II) et fer(III) ont été isolé comme étant des produits secondaires de la réaction. Dans le but de caractériser les produits obtenus, nous avons aussi préparé plusieurs dérivés en introduisant des ligands supplémentaires dans la sphère de coordination; c’est ainsi que des dérivés formiate, carboxylate, triflate et cyclopentadiényle ont été synthétisés. Plusieurs voies ont été exploitées pour synthétiser les complexes fer(II) bisimidazol-2-ylidene, une d’elles, la transmetallation, nous a conduit à préparer des nouveaux complexes d’argent; ces complexes ont été caractérisés entre autre par diffraction de rayons – X. Enfin dans une démarche purement comparative, deux complexes nickel bisimidazol-2-ylidene ont été préparés et leur activité catalytique dans la polymérisation d’éthylène a été sommairement étudiée, donnant de très bons résultats.The use of organometallic complexes as catalysts became a very significant topic in the field of material chemistry. However, despite of this development, only few of them contain iron(II), except the tridentate complex diimine pyridine developed by Gibson and Brookhart and employed in the olefin polymerization. Unfortunately, this model suffers by its lack of tolerance towards the minor changes carried out in its envelope, resulting by a drastic reduction from its catalytic activity. The goal of this work is to synthesize iron(II) complexes containing pincer ligands and to study their use as catalyst for polymerization of olefins. It has to be noted that previous work in our group showed a very good correlation between the polymerization and the hydrogenation of olefin. Thus, we have also exploited the ability of our news complexes in hydrogenation. Two projects were carried out in parallel: one was the synthesis of iron(II) complexes containing benzyletherfuran ligand and the second one was the preparation of iron(II) bisimidazol-2-ylidene complexes. First project : The prepared iron(II) benzyletherfuran complex was successfully tested in the hydrogenation of olefin under very mild conditions (1-3 bar of hydrogen at room temperature); however, its employment as catalyst for olefin polymerization did not give the expected results. Thus, this project was left aside with the profit of the second one. Second project : The prepared iron(II) bisimidazol-2-ylidene complexes showed a good activity in both reactions, polymerization and hydrogenation of olefins under mild conditions. During the preparation of these complexes, several other complexes of iron(II) and iron(III) were isolated as secondary products from the reaction. With the purpose of characterizing the obtained products, we also prepared several derivatives by introducing additional ligands into the coordination sphere of iron(II) bisimidazol-2- ylidene complexes. Thus, formiate, carboxylate, triflate and cyclopentadienyl derivatives were synthesized. Several ways were exploited to synthesize the iron(II) bisimidazol-2-ylidenes complexes, one of them was the transmetallation which led us to prepare new silver complexes. These complexes were characterized amongst other analytical tools by X-ray diffraction. Finally, in a purely comparative approach, two nickel bisimidazol-2-ylidene complexes were prepared and their catalytic activity in the ethylene polymerization was studied, giving very good results

Chemical nucleation of diamond films

With the large differences in surface energy between film and substrate in combination with the low sticking coefficient of hydrocarbon radicals, nanocrystalline diamond growth on foreign substrates typically results in poor nucleation densities. A seeding technique is therefore required to realize pinhole-free and thin coalesced films. In this work, a chemical nucleation method for growth of diamond on nondiamond substrates based on 2,2-divinyladamantane is shown. After treating with the carbon-containing DVA, the chemically treated wafers were exposed to low-power-density plasma, known as the incubation phase, to facilitate the formation of diamond nucleation sites followed by a high-power-density growth regime to produce coalesced films. The resulting films demonstrate high crystallinity, whereas the Raman spectra suggest high-quality diamond with low sp² content

Chemical nucleation of diamond films

With the large differences in surface energy between film and substrate in combination with the low sticking coefficient of hydrocarbon radicals, nanocrystalline diamond growth on foreign substrates typically results in poor nucleation densities. A seeding technique is therefore required to realize pinhole-free and thin coalesced films. In this work, a chemical nucleation method for growth of diamond on nondiamond substrates based on 2,2-divinyladamantane is shown. After treating with the carbon-containing DVA, the chemically treated wafers were exposed to low-power-density plasma, known as the incubation phase, to facilitate the formation of diamond nucleation sites followed by a high-power-density growth regime to produce coalesced films. The resulting films demonstrate high crystallinity, whereas the Raman spectra suggest high-quality diamond with low sp2 content

Tribenzopentaphene derivatives with lateral aromatic groups: the effect of the nature and position of substituents on emission properties

Nine new derivatives of the trapezoidal tribenzopentaphene (TBP) polycyclic aromatic hydrocarbon (PAH) were synthesized via the Suzuki–Miyaura palladium catalyzed cross-coupling reaction. The novel TBP derivatives, which bear various rigid and flexible aromatic groups either at their more accessible (R1) or congested (R2) bases, were fully characterized using high resolution mass spectrometry (HR-MS), nuclear magnetic resonance (NMR), UV-Vis absorption and emission spectroscopy. Our investigation reveals that extended conjugation between TBP and the aromatic side groups is possible when the latter are carefully selected and attached at the TBP wide base (R1), which causes an emission red-shift of the resulting target compounds. On the other hand, emission properties and density functional calculations suggest that attaching side groups at the sterically demanding base position (R2) induces a pronounced distortion from the planarity of the TBP central core structure