Thierry Renouard

Recovery of Enlarged Olefin Metathesis Catalysts by Nanofiltration in an Eco-Friendly Solvent

This study was aimed at integrating a green separation process without phase change, namely nanofiltration, with olefin metathesis to recover the homogeneous catalyst. As the commercially available Hoveyda II catalyst was not sufficiently retained by the membrane, a set of homogeneous ruthenium-based catalysts were prepared to enhance the recovery of the catalyst by solvent-resistant commercial membranes made of polyimide (Starmem 228). The molecular weights of the catalysts were gradually increased from 627 to 2195 g mol(-1), and recovery was found to increase from around 70 % to 90 % both in toluene and dimethyl carbonate. The most retained catalyst was then engaged in a series of model ring-closing metathesis reactions associated to a final nanofiltration step to recover and recycle the catalyst. Up to five cycles could be performed before a deterioration in the performance of the process was observed.

New bipyridyl ligands bearing azo- and imino-linked chromophores. Synthesis and nonlinear optical studies of related dipolar zinc complexes†

The synthesis and optical properties of 4,4′-bis(dialkylaminophenylazo)-2,2′-bipyridine and 4,4′-bis(dialkylaminophenylimino)-2,2′-bipyridine ligands are described; the corresponding dipolar bipyridyl zinc dichloride complexes have been prepared and their second order nonlinear optical properties determined by electric field-induced second harmonic generation (EFISH) at 1.34 µm.

Tetrahedral bipyridyl copper(I) complexes: a new class of non-dipolar chromophore for nonlinear optics

The synthesis of 4,4′-bis(dialkylaminostyryl)-6,6′-dimethyl-2,2′-bipyridine ligands is described; the corresponding tetrahedral bis(bipyridyl) copper(I) complexes have been prepared, and their second-order nonlinear optical properties determined by harmonic light scattering (HLS) at 1.34 µm; these new octupolar complexes exhibit large molecular hyperpolarisabilities β.

Pyrolyzed Hexakis(p-bromophenyl)benzene as Anode Material for Li Batteries Structural and Electrochemical Aspects

A low-temperature pyrolytic stepwise method is proposed to produce substantial amount of a carbonaceous material, characterized by a graphenic structure. The pyrolyzed material has been submitted to ballmilling steps of different times, and the samples obtained were studied from their structural and electrochemical points of view. The crystallographic data have evidenced crystallites with a crystal domain size less than one nanometer and the grinding influence is discussed. Electrochemical experiments have been carried out in order to study the mechanism of the Li insertion/deinsertion process in the host material. Interesting values of Li specific capacity have been calculated from cycle experiments in Li coin cells at constant current and a test in a Li-ion laboratory-type cell is proposed.

Electronic structure of Li-intercalated oligopyridines: A comparative study by photoelectron spectroscopy

The role of nitrogen in the charge transfer and storage capacity of lithium-intercalated heterocyclic oligophenylenes was investigated using photoelectron spectroscopy. The development of new occupied states at low binding energies in the valence band region, as well as core level chemical shifts at both carbon and nitrogen sites, demonstrates partial charge transfer from lithium atoms to the organic component during formation of the intercalated compound. In small compounds, i.e., biphenyl and bipyridine derivatives, the position of the nitrogen heteroatom significantly affects the spacing between gap states in the Li-intercalated film; yet it has minimal effects on the charge storage capacity. In larger, branched systems, the presence of nitrogen in the aromatic system significantly enhances the charge storage capacity while the Li-N bond strength at high intercalation levels is significantly weakened relative to the nitrogen-free derivative. These observations have strong implications towards improved deintercalation processes in organic electrodes in lithium-ion batteries.