Jérôme Durand

Theoretical and Experimental Studies on the Carbon‐Nanotube Surface Oxidation by Nitric Acid: Interplay between Functionalization and Vacancy Enlargement

The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or carboxylic groups. At room temperature, this reaction takes place on the most reactive carbon atoms. At higher temperatures a different mechanism would operate, as evidenced by the difference in activation energies. Experimental data can be partially related to first-principles calculations, showing a multistep functionalization mechanism. The theoretical aspects of the present article have led us to propose the most efficient pathway leading to carboxylic acid functional groups on the surface. Starting from mono-vacancies, it ends up with the synergistic formation of dangling -COOH groups and the enlargement of the vacancies.

Palladium catalyzed Suzuki C–C couplings in an ionic liquid: nanoparticles responsible for the catalytic activity

A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system.

Ethylene Polymerization Catalyzed by Pyrene‐Tagged Iron Complexes: The Positive Effect of π‐Conjugation and Immobilization on Multiwalled Carbon Nanotubes

2‐[1‐(2,6‐Diisopropylphenylimino)ethyl]‐6‐[1‐(pyren‐1‐ylimino)ethyl]pyridine (L1) and 2,6‐bis[1‐(pyren‐1‐ylimino)ethyl]pyridine (L2) were synthesized and used to prepare the corresponding Fe complexes Fe1 and Fe2 from FeCl2. All new compounds were characterized, and single‐crystal XRD analysis of Fe1 was performed. The π‐conjugated pyrenyl substituent enhanced the catalytic activity of the Fe complexes, which display high activity in ethylene polymerization up to 107 gPE molFe−1 h−1 (PE=polyethylene). These Fe complexes were easily immobilized on multiwalled carbon nanotubes (MWCNTs) through noncovalent π–π interactions. The supported precatalysts showed better ethylene polymerization activity than their homogeneous counterparts to produce well‐dispersed MWCNT/PE composite materials.

Heterobimetallic intermediates in alkene insertion reactions into a Pd–acetyl bond

The reactivity of diphosphine-bridged heterobimetallic Fe–Pd alkyl complexes was evaluated for the insertion of CO, isonitriles, ethylene, methyl acrylate and norbornadienes and the crystal structures of the precursor alkyl complex, the iminoacyl derivative and the five-membered ring complex resulting from ethylene insertion into the palladium–acyl bond are reported.

Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes

The confinement of air-protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer-precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface-modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT-confined iron nanoparticles coated with a polyisoprene air barrier. This approach constitutes a proof of concept for the development of smart materials for use in medicine or composites.