Time filter

Source Type

Garcia Y.,Catholic University of Louvain | Ksenofontov V.,Johannes Gutenberg University Mainz | Lapouyade R.,National Graduate School of Chemistry and Physics, Bordeaux | Naik A.D.,Catholic University of Louvain | And 2 more authors.
Optical Materials | Year: 2011

The coordination compound Fe(BM-4-PTP)2(NCS)22MeOH (1) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl- 5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5-293 K) and pressure range (1 bar-12 kbar) by magnetic susceptibility measurements and variable temperature 57Fe Mössbauer spectroscopy. The photo-induced colour change is accompanied by a distinct magnetic variation at room temperature. Potentialities of this functional optical material for display and data recording are introduced. © 2010 Elsevier B.V. All rights reserved.

Dufresne S.,University of Montreal | Roche I.U.,University of Montreal | Roche I.U.,National Graduate School of Chemistry and Physics, Bordeaux | Skalski T.,University of Montreal | And 2 more authors.
Journal of Physical Chemistry C | Year: 2010

A series of oligofluorenes containing arylketylimines in the 9-position ranging between 1 and 3 fluorene segments was prepared. The conjugated ketylimines were prepared using dehydration and Lewis acid protocols from the corresponding oligofluorenones. These heteroconjugated oligomers were prepared for examining the effect of the ketylimine moiety on the photophysical properties relative to their ketone counterparts. Both the ketylimine and fluorenone containing oligofluorenes exhibited reduced fluorescence relative to their corresponding all-fluorene analogues. Temperature-dependent emission measurements and steady-state fluorescence quenching confirmed that fluorescence deactivation of the ketylimines occurred predominately by intramolecular photoinduced electron transfer (PET). This is in contrast to their oligofluorenone counterparts that dissipated their singlet excited state energy via both intersystem crossing and nonradiative internal conversion. The measured diffusion controlled fluorescence quenching rate constants (3 × 10 10 M-1 s-1) combined with the calculated exergonic energetics ranging from -10 to -116 kJ/mol derived from the Rehm-Weller equation for the oligofluorenyl ketylimines corroborate that the ketylimines' fluorescence deactivation occurs by intramolecular PET. © 2010 American Chemical Society.

Delbosc N.,National Graduate School of Chemistry, Montpellier | Reynes M.,National Graduate School of Chemistry, Montpellier | Dautel O.J.,National Graduate School of Chemistry, Montpellier | Wantz G.,National Graduate School of Chemistry and Physics, Bordeaux | And 2 more authors.
Chemistry of Materials | Year: 2010

A new approach toward the tuning of the supramolecular organization of π-conjugated substructures containing imide functional groups has been investigated using the concept of supramolecular chemistry. This approach, which allows enhanced emission properties of the active material, was evaluated in the fabrication of optoelectronic devices. A linear ditopic chromophore H-ImPV was synthesized. This N-H imide constitutes a recognizing unit with an acceptor-donor-acceptor (ADA) hydrogen bond motif. End-capping of this new chromophore with a monotopic structuring unit allowed control of the supramolecular aggregation of the π-conjugated chromophore. The studies of the absorption and emission properties of the H-ImPV, in solution or in the solid state (thin films, powders), clearly revealed different aggregation behaviors, depending on the presence of the monotopic structuring unit: hindered unit (Cy-DAT) led to the formation of J-aggregates. In all cases, evidence for the heteromolecular association H-ImPV⋯Cy-DAT was obtained from an infrared absorption band located at 2715 cm -1, which was typical of the hydrogen bonding present in the ADA⋯DAD triplet. This has been illustrated by the fabrication of light-emitting devices based on films of H-ImPV and [H-ImPV.(Cy-DAT) 2]. H-ImPV presents a poor ability to emit light, because of its aggregation, which induces quenching of luminescence. The high efficiencies exhibited by the devices based on a single layer of [H-ImPV.(Cy-DAT) 2] are the result of the J-aggregation of chromophores, because of the bulky cyclohexyl fragments of the Cy-DAT. Tuning of the supramolecular organization of the H-ImPV by the addition of two equivalents of Cy-DAT in the active layer allowed recovery of the performances exhibited by the organic light-emitting devices (OLEDs) of the isolated chromophore. Therefore, the use of Cy-DAT is an interesting alternative to avoid aggregation and to significantly increase luminance. As a consequence, the luminous efficiencies of the devices are much better for the coassembled active layer. © 2010 American Chemical Society.

Bodennec M.,National Graduate School of Chemistry and Physics, Bordeaux | Guo Q.,Ryerson University | Rousseau D.,Ryerson University
RSC Advances | Year: 2016

The molecular and microstructural organization of lecithin/canola oil oleogels as a function of water content, lecithin concentration and temperature were explored using rheology, polarized light microscopy, confocal microscopy and X-ray diffraction. Using a partial phase diagram, a large gel region consisting of 10-30 wt% of lecithin was formed. The range of wo values (molar ratio of [H2O]/[lecithin]) leading to gel formation at high lecithin concentration (30 wt%) was broader (wo = 0.28-2.78) than at low concentration (10 wt%) (wo = 1.25-1.67). Rheology results showed that the gels (wo = 1.40) transitioned to liquids at 50-55 °C regardless of lecithin concentration (10, 20 and 30 wt%). Small-angle X-ray diffraction at 25 °C revealed a reverse hexagonal (HII) lattice structure with a d-spacing of 52 Å and liquid crystallites ∼1200 Å in length that rearranged with temperature evolving towards a less-ordered isotropic fluid unable to gel. At the microscale, gels showed a 3D network composed of microfibres with an average diameter of ∼1 μm. The proposed self-assembly mechanism is based on the packing of reverse hexagonal tubules parallel to the axis of fibres. The gel network forms due to branching and overlapping of these bundles at junction zones along the reverse micellar chains. In conclusion, lecithin and water content underpinned the structure and morphology of these oleogels. © The Royal Society of Chemistry 2016.

Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: NMP-2007-2.4-2 | Award Amount: 3.72M | Year: 2008

The aim of the project is the development of electrochemical reactors for the manufacture of fine chemicals with dehydrogenases as a process with almost zero waste emission. The production of enantio pure compounds with high EEs can be achieved by using dehydrogenases as biocatalysts, because they express high enantio selectivity in ketone reduction, combined with broad substrate spectra by some of these enzymes. These proteins will be engineered for improved catalytic performance using the tools of molecular evolution, modelling, structure prediction, and crystallography. As these dehydrogenases typically require cosubstrate regeneration by aid of a second enzymatic reaction, we are looking for the alternative solution of an electrochemical approach for the regeneration of reduced cofactors. If all active compounds can be functionally immobilized on the electrode surface the constructed reactor would convert the educt in the input flow to the product in the output flow avoiding any contaminations. All necessary components like the mediator, the cofactor and the dehydrogenase will be bound to nano or meso structured electrodes (for increased active surface area) resulting in biofunctionalised surfaces with tailored properties at the nanoscale. Optimization of the electrode materials and surfaces, of the mediators and the required spacers as well as the surface bound dehydrogenase activities will result in electrochemical reactor moduls which can deliver enantio pure synthons for desired compounds in pharmaceutical or agrochemical applications. The obtained data will increase our knowledge on nanostructured catalysts and inorganic-organic hybrid systems. Cheap cofactor regeneration, easy product purification, high selectivity and avoidance of organic solvents will be the advantages of such processes to satisfy the demands of green chemistry in respect of environmentally friendly, flexible and energy efficient productions.

Discover hidden collaborations