Michel Jubault

Novel narrow bandgap polymers from sp3 carbon-bridged bithienyls: poly(4,4-ethylenedioxy-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)

A hydrophilic conjugated polymer with a bandgap of 1.2 eV has been obtained by electropolymerization of 4,4-ethylenedioxy-4H-cyclopenta[2,1-b;3,4-b′]dithiophene.

Acetylenic analogs of tetrathiafulvalene: alkynes-hexacarbonyldicobalt complexes mediated synthesis and Π-donor properties

Abstract The title compounds are prepared through Wittig or Wittig-Horner reactions between the dicobalthexacarbonyl complexes of acetylenedicarbaldehyde C1 or its acetal C2 and the phosphoranes W or the phosphonates anions P bearing the 1,3-dithiole-2-ylidene moiety, the final decomplexation being achieved with trimethylamine oxide ; their π-donor properties are also presented.

Electro-oxidation of substituted conjugated sexithienyls

Abstract A new series of conjugated α-sexithienyls derivatized by alkyl and oxyalkyl groups has been synthesized. Although of comparable electronic inductive effects, these substituents produce important differences in the electrochemical behavior of the π-conjugated system. Long alkyl or oxyalkyl chains lead to an enhancement of electrochemical reversibility and a stabilization of the cation radical state. The electrodeposition of these oligomers has been achieved by means of recurrent potential scans. Analysis of the electrodeposition process and of the electrochemical behavior of the resulting materials suggests that, whereas in polar solvents radical coupling occurs and leads to extensively conjugated polymers, in methylene chloride electrodeposition seems to proceed via the di-cation state and to produce essentially the corresponding di-cation salt.

Synthesis and liquid crystal behaviour of tetrathiafulvalenes containing cyanobiphenylyloxy groups

The synthesis and characterization of a series of tetrathiafulvalenes (1–3) bearing a different number of 4′-cyanobiphenyl-4-yloxy side groups is reported. Compound 3 exhibits a nematic and a smectic A mesophase. In the smectic A phase a peculiar local biaxial order due to the unconventional molecular structure is proposed. A charge-transfer salt derived from 3, namely 3·I5 , also shows mesogenic behaviour.

Small bandgap molecular semiconductors based on rigidified tetrathiafulvalene–bithiophene hybrid conjugated systems

Rigidified tetrathiafulvalene–bithiophene hybrid systems with multi-step oxidation and reduction stages and bandgaps <1.5 eV have been synthesized.

Synthese asymetrique par voie electrochimique—III. stereochimie de la reduction du phenylglyoxylate de (−)menthyle☆

Electrochemical reduction, at a mercury cathode, of (-)menthyl phenylglyoxylate, leads to a mixture of the two epimers of (-)menthyl mandelate, the respective proportions of which depend on numerous factors. The R(-) mandelate is nearly always preferentially obtained and the experimental data are in good agreement with the following hypothesis: in very acidic media, protonization of the intermediate carbanion occurs principally at the side of the molecule near by the electrode surface, before inversion of the initial configuration of the carbanion; in neutral or basic media, protonization takes place essentially in the solution. The way of presentation of the substrate at the electrode, the working potential and the components of the electrical double layer, act also as determining factors.

Effect of heteroaromatic spacers on the structure and electrical properties of cation radical salts of tetrathiafulvalene analogs

The X-ray crystal structure of single crystals of electrocrystallized cation radical salts of 2,5-bis(1,3-dithiol-2-ylidenemethyl)-thiophene and -furan1and2 have been analysed. Both cation radicals adopt asyn conformation stabilized by strong intramolecular interactions. Bond length analysis reveals that the positive charge is delocalized over the whole molecule with enhanced delocalization for 2+ containing the less aromatic furan cycle. Whereas 2+ cation radicals are uniformly stacked along the c axis with interstack interactions, 1+ forms weakly interacting dimers stacked along the b axis. In agreement with an enhanced charge delocalization and increased dimensionality, 2BF4 shows a conductivity ca. three orders of magnitude higher than 1ClO4 .

Synthese asymetrique par voie electrochimique—IV. Mise en evidence et etude polarographique des interactions substrat-inducteur adsorbe

Different derivaties of the type C6H5C(Z)CO2R, where ZO or NOH and R  H or CH3, have been studied. Their polarographic behaviour has been compared, both in the absence and in the presence of adsorbed cations (strychninium or N-methylstrychninium) which may act as asymmetric inductors. In acidic media, the reduction waves of these compounds are frequently mixed surface-volume waves, characteristic of a preliminary protonation, before the charge transfer. A surface active proton donor increases the limiting-current of a kinetic wave. Moreover, the adsorbed cations modify the surface of the electrode and its immediate vicinity; therefore, considerable changes are observed as for the pH dependence of the half-wave potentials. These phenomena are very dependent upon the nature of the reducible function. We suggest that these results could have an important, but not determining significance in the complex problem of the asymmetric induction.

Regioselective electroreduction of 6H-1,3-thiazines, comparison with chemical reductions. I: Investigation of 2-phenyl-6H-1,3-thiazines

The electrochemical reduction of 2-phenyl-6H-1,3-thiazines carried out at a mercury cathode in acetate buffer + ethanol (1:1) has been studied : - In the case of compounds monoactivated at carbon 5 (R5 = CHO or COCH3) either hydrodimers (resulting from coupling at C-2), 3,6-dihydro-2H-1,3-thiazines (reduction of the imine bond) or tetrahydrothiazines can be obtained. - Diactivated 6H-1,3- thiazines (R4 = CO2Et, R5 = CHO or COCH3) successively lead to 5,6-dihydro-4H-1,3-thiazines (reduction of the ethylenic bond) and tetrahydrothiazines. - The reduction of a 6H-1,3-thiazine bearing only one withdrawing group at carbon 4 gives rise to a ring opening. At the same time, the action of various chemical reducing agents has been examined : the reduction of the imine bond is performed using NaBH3CN while NaBH4 or LiAlH4 leads to the reduction of the substituents on the heterocyole.

Tetraformyltetraselenafulvalene (TFTSeF): synthesis and some uses as a precursor of polyfunctionalized tetraselenafulvalenes

A short synthesis of tetraformyltetraselenafulvalene (TFTSeF) is presented, and a few preliminary results emphasize its use as an efficient precursor of tetrasubstituted TSeFs such as a tetravinylic derivative, via a Wittig reaction, and tetrakis(hydroxymethyl)–TSeF by a simple NaBH4 reduction.