Jia H.-P.,CNRS Institute of Chemistry |
Quadrelli E.A.,CNRS Institute of Chemistry
Chemical Society Reviews | Year: 2014
Dinitrogen cleavage and hydrogenation by transition-metal centers to produce ammonia is central in industry and in Nature. After an introductory section on the thermodynamic and kinetic challenges linked to N2 splitting, this tutorial review discusses three major classes of transition-metal systems (homogeneous, heterogeneous and biological) capable of achieving dissociation and hydrogenation of dinitrogen. Molecular complexes, solid-state Haber-Bosch catalytic systems, silica-supported tantalum hydrides and nitrogenase will be discussed. Emphasis is focused on the reaction mechanisms operating in the process of dissociation and hydrogenation of dinitrogen, and in particular on the key role played by metal hydride bonds and by dihydrogen in such reactions. © The Royal Society of Chemistry.
Fromager E.,CNRS Institute of Chemistry
Molecular Physics | Year: 2015
The exact formulation of multi-configuration density-functional theory is discussed in this work. As an alternative to range-separated methods, where electron correlation effects are split in the coordinate space, the combination of configuration interaction methods with orbital occupation functionals is explored at the formal level through the separation of correlation effects in the orbital space. When applied to model Hamiltonians, this approach leads to an exact site-occupation embedding theory (SOET). An adiabatic connection expression is derived for the complementary bath functional and a comparison with density matrix embedding theory is made. Illustrative results are given for the simple two-site Hubbard model. SOET is then applied to a quantum chemical Hamiltonian, thus leading to an exact complete active space site-occupation functional theory (CASSOFT) where active electrons are correlated explicitly within the CAS and the remaining contributions to the correlation energy are described with an orbital occupation functional. The computational implementation of SOET and CASSOFT as well as the development of approximate functionals are left for future work. © 2015 © 2015 Taylor & Francis.
Hiebel M.-A.,CNRS Institute of Chemistry |
Berteina-Raboin S.,CNRS Institute of Chemistry
Green Chemistry | Year: 2015
An iodine-catalyzed sulfenylation of imidazo[1,2-a]-pyridines, -pyrimidines, and [1,2-b]pyridazines is herein described with various thiophenols using hydrogen peroxide as an oxidizing agent in PEG400. The method enabled the formation of 3-arylthioimidazoheterocycles in moderate to excellent yields under metal-free conditions. Several functional groups were well tolerated under our optimized conditions. This journal is © The Royal Society of Chemistry 2015.
Nicolas M.,CNRS Institute of Chemistry
Journal of Colloid and Interface Science | Year: 2010
Over the past few years, electropolymerization of semifluorinated monomers like thiophene or pyrrole has been used as a gentle and effective method to generate, in one step, stable superhydrophobic surfaces. The synthetic route mostly involves the coupling reaction between a carboxylic acid and an alcohol, using a carboxy group-activated reagent and a catalyst. As a consequence, the electroformed surfaces present high liquid repellency due to the concomitant effect of roughness and low surface energy. Nevertheless, the ester connector can be cleaved under acidic and basic conditions, preventing its use under a range of environmental conditions. To overcome this drawback, a new perfluoroalkyl alkyl pyrrole has been synthesized, the fluorinated segment being connected to the electropolymerizable part via an alkyl chain, and electropolymerized, leading to surfaces that exhibit a static contact angle with water superior to 150° and no sliding angle, over a wide pH range and with a long lifetime. This represents the first example of a pure conducting polymer surface with sticky superhydrophobicity not only in pure water but also in corrosive solutions such as acids and bases, giving rise to new prospects in practical applications. © 2009 Elsevier Inc. All rights reserved.
Baddour-Hadjean R.,CNRS East Paris Institute of Chemistry and Materials Science |
Pereira-Ramos J.-P.,CNRS East Paris Institute of Chemistry and Materials Science |
Pereira-Ramos J.-P.,CNRS Institute of Chemistry
Chemical Reviews | Year: 2010
Raman spectroscopy can be used for better understanding of the relationship between the structure and electrochemistry of electrode materials for lithium batteries. Most of the electrode materials, including carbonaceous compounds, transition metal oxides, and phospho-olivines, are Raman active compounds. Raman spectroscopy constitutes a very pertinent local tool to enrich the knowledge of the structure of Li intercalation compounds at the scale of interatomic bonds by providing information regarding local disorder, changes in bond lengths, bond angles, coordination, Li dynamics, metal oxidation state, and cation ordering. New and pertinent data allowing the identification of the local processes that contribute to the mechanism of Li- battery degradation on cycling or aging have been obtained from the great possibilities offered by the confocal Raman imaging technique. The ultimate step for a significantly improved and wider application of Raman microspectrometry will consist in systematically combining a rigorous experimental approach with appropriate lattice dynamics simulations.
Coperet C.,CNRS Institute of Chemistry
Chemical Reviews | Year: 2010
A study was conducted to investigate C-H bond activation and organometallic intermediates on isolated metal centers on oxide surfaces. It was demonstrated that C-H bond activation was a ubiquitous process in heterogeneous catalysis that involved various types of mechanisms and intermediates. The study focused on investigating processes that involved C-H bond activation of alkenes and aromatics on isolated metal centers of surface oxide materials leading to organometallic species and intermediates. One potential pathway in alkene dehydrogenation involved the formation of a metal-alkyl intermediate that underwent β-H elimination and generated an alkene. It was demonstrated that cofeeding CO2 increased the activity and the stability of these nonoxidative dehydrogenation catalysts, as CO2 played the role of a mild oxidant and prevented coke formation.
Alam M.M.,CNRS Institute of Chemistry
Physical Chemistry Chemical Physics | Year: 2014
In the present work, we address the question-"which among the electron donors and the electron acceptors contribute more to the two-photon (TP) activity of a donor-π-acceptor type of molecule?" For this purpose we have performed ab initio calculations to calculate the TP transition probability (δTP) of a recently synthesized (Benedetti et al., J. Am. Chem. Soc., 2012, 134(30), 12418-12421) cyclopenta[b]naphthalene based chemo-sensor and its derivatives containing different electron donor and acceptor groups. Our study revealed that both under vacuum and in solvent phases, an increase in electron donor strength (-OMe, -NH2, -NMe2) increases the δTP value up to five times, whereas, an increase in the acceptor group strength (-COCH3, -NO2, -CN) increases it by a factor of two only. The highest δTP value is obtained for the molecule having the strongest donor-acceptor pair (-CN, -NMe2) considered in this work. We have also noted that, the removal of the cyclopentane ring from the original system increases the δTP value by ∼20% and the replacement of the naphthyl group by the benzene ring decreases it by ∼70%. All these results are explained by inspecting different TP tensor elements and different transition moment vectors involved in a two-state model approach. A close scrutiny of different parameters in 2SM clearly reveals that upon increasing the strength of either the donor or the acceptor group the parameters change in favour of increasing the overall δTP values but in the case of donors this effect is much larger. This journal is © the Owner Societies.
Boutinaud P.,National Graduate School of Chemistry of Clermont Ferrand |
Boutinaud P.,CNRS Institute of Chemistry
Inorganic Chemistry | Year: 2013
A model is introduced to predict the energy of metal-to-metal charge-transfer transitions in oxide compounds containing Bi3+ ions and d0 or d10 metals (Mn+). The model takes into account the structural characteristics of the host lattices, the anion relaxation resulting from Bi3+ doping, and the electronegativities and coordination numbers of the Bi3+ and Mn+ ions in the compounds. It is shown, through a critical review of the archival literature, that this model provides new insights on the assignment of the luminescence spectra and the related interpretation of the spectroscopic behaviors. © 2013 American Chemical Society.
Conley M.P.,ETH Zurich |
Coperet C.,ETH Zurich |
Thieuleux C.,CNRS Institute of Chemistry
ACS Catalysis | Year: 2014
Engineering heterogeneous catalysts with molecular precision is an ongoing challenge to access materials with predictable properties that can be optimized using quantitative structure-activity relationships. One approach is grafting organometallic complexes on dehydroxylated oxide supports using surface organometallic chemistry (SOMC). Although fruitful, this technique is limited to complexes containing a σ-bound surface oxygen in the first coordination sphere of the metal. In this perspective, we describe our recent efforts to incorporate molecular diversity onto surfaces to obtain molecularly defined heterogeneous catalysts containing N-heterocyclic carbene ligands for C-H activation, olefin metathesis, CO2 hydrogenation, and the Z-selective semihydrogenation of alkynes. © 2014 American Chemical Society.
Bechinger B.,CNRS Institute of Chemistry
Journal of Peptide Science | Year: 2011
In order to better understand the mechanisms of action of linear cationic host defense peptides, biophysical and structural investigations of their interactions with membranes and with other biomacromolecules are reviewed. In particular, an extensive overview will be given of the topological studies of magainins in a number of different lipid environments. Furthermore, amphipathic helices have been designed in such a manner to allow the easy control of their membrane alignment. These peptides not only exhibit potent antimicrobial and transfection activities, but their investigation has also provided important insights into mechanistic aspects of their biological functions. © 2011 European Peptide Society and John Wiley and Sons, Ltd.