Effects of structural factors on the pi-dimerization and/or disproportionation of the cation radical of extended TTF containing thiophene-based pi-conjugated spacers.

The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5·BF4(CH2Cl2) and 4·ClO4(THF)1/2 are presented. The effects of structural factors on the π-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH3CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH3CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))2+ is due mainly to π–π interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S–S and π–π interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4+· to dimerize with the occurrence of dimer and monomer in solution, while for 5+· only the monomer is detected in DCM. On the other hand, by dissolution of 5·BF4(CH2Cl2) in CH3CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

EPR AND ELECTROCHEMICAL STUDIES OF THE SYSTEM Li+(C2 H5NH2)x.Na-

Very concentrated solutions of lithium and sodium can be obtained in ethylamine when these alkali metals are put in contact together in this solvent. The major species in presence are solvated lithium cations and sodium anions. The stoechiometry of the solution can be written as Li+(C2H5NH2)x.Na-. The liquid corresponding to x = 4 is highly viscous and has a bronze metallic luster. Impedance measurements indicate that for x > 10, the behavior of the solution is similar to that of ordinary sodides in the same solvent. When x becomes close to 4, highly conducting systems are obtained. EPR spectroscopy measurements show only a single line having a g-value close to that of the free electron whose width increases as the temperature is decreased. A discontinuity is observed at about the freezing temperature of the solvent, but a paramagnetic signal is still present in the solid state. Band shape analysis indicates complex systems of several gaussian lines. "Dysonian" lines, characteristic of the onset of a metallic state, were never observed

PHOTOLYSIS OF SOLID Na+C222.Na- BY AN EXCIMER LASER PULSE AT 308 nm

Illumination of thin dry films of Na+C222.Na- by short pulses of UV light at 308 nm produces modifications of the optical absorption spectrum similar to those obtained by visible light irradiation. These effects are interpreted in terms of transfer and recombination from the conduction band of the sodide. The quasi reversibility observed in the case of UV irradiation indicates that the process does not involve the 3s3p excited state. Deconvolution of the optical spectrum observed before and after the flash provides informations on the number of absorbing species. Preliminary results obtained with a variety of other sodides are shortly discussed

First evidence of the oxidation and regeneration of polysulfides at a GaAs electrode, under anodic conditions. A study by in situ UV - visible spectroelectrochemistry

We report on the oxidation and regeneration, at a GaAs electrode, of polysulfides present in (NH4)2Sn aqueous solutions. The concentration of the polysulfide ions can be monitored by optical absorption spectroscopy. Thus, the variation of their concentration at a "GaAs/(NH4)2Sn solution" interface, under anodic potential, was followed by in situ UV-visible spectroelectrochemistry performed in thin layer conditions and in galvanostatic mode. Under these conditions, the variation of the solution absorption at the interface allowed us, on one hand, to confirm that the polysulfides are oxidized at a GaAs electrode, leading to the release of S, and, on the other hand, to underscore that S reacts with HS- ions to restore polysulfides. Moreover, it was shown that the main polysulfide species present in a 1% (NH4)2Sn aqueous solution is the pentasulfide ion, S52-. Finally, this work shows that under definite conditions of anodic current and electrolyte composition, the surface of the GaAs anode is neither oxidized nor passivated

Le potentiel aromatique de la Syrah : influence de l'environnement de la vigne

National audienc

Biogenesis of C13-norisoprenoids in grape: biotransformation of C13-norisoprenoids by a cell suspension culture of cv. Gamay

National audienc

Importance des propriétés optiques de la surface du sol sur le microclimat de la vigne, répercussions de l'usage d'un revêtement de sol réfléchissant sur la composition des mouts et sur la qualité du vin.

National audienc

Reinforcement of the radiative and thermic stresses of the grapevine in field conditions using a reflective soil cover. Repercussions on the must composition and on the wine quality.

International audienc

Stress thermohydrique et qualité du vin

National audienc