E. Raoult

Anodic polymerization of N-(9-fluorenylmethoxycarbonyl)amino acids towards chiral conducting polymers

The anodic oxidation of several fluorenylmethoxycarbonyl-amino acids is described. Insoluble electroactive polymers with conservation of the methoxycarbonyl-amino acid unit on the polyfluorene backbone are obtained. The chiral discrimination of these materials towards pure enantiomers is presented.

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.

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.

Synthesis and electrochemistry of a novel polyfluorenylidene containing ferrocene units

A novel fluorenylidene containing a ferrocene unit has been electropolymerized. In this polymer, the ferrocene unit is grafted to the main polyfluorenylidene chain as a pendant group. The polymer is electroactive in non-aqueous and aqueous media.

New electrochemically synthesized mixed polymers with very high electrochemical stability

The electrosynthesis of new mixed polymers is described, starting with the anodic oxidation of a mixture of 3,4-ethylenedioxythiophene: EDOT and dicyanomethylenefluorene: DiCNFl. The resulting mixed polymer possesses a very high electrochemical stability and good electrochromic properties. Copyright

Synthese asymetrique par voie electrochimique—VI. Etudes en double induction

The electrochemical reduction of (−) menthyl phenylglyoxylate is performed at a mercury cathode in the presence of various additional compounds. These compounds may be more or less adsorbed, chiral or not and more or less efficient as proton donating species. This study shows that optical yield depends on the working potential and the proton donating ability of the solution. Experimental results are in good agreement with the hypothesis of a kinetic competition between the electric field effects (inversion of the intermediate carbanion and its repulsion towards the solution) and protonation of this carbanion either in the near vicinity of the electrode or in the bulk of the solution.

Electrochemical access to functionalized dihydrothiopyran derivatives-Part 2. Electroreduction of triactivated 4H-thiopyrans

Electrochemical behaviour of triactivated thiopyrans has been investigated in protic medium. Electroreduction of 4-dimethylamino-2,3,5-trimethoxycarbonyl-4H-thiopyran I first led to 2,3, 5-trimethoxy-carbonyl-2H-thiopyran IV, with elimination of dimethylamine; further reduction at more negative potential gives equimolar mixture of 2,3,6-trimethoxycarbonyl-3,6-dihydro-2H-thiopyran V and 2,3, 6-trimethoxycarbonyl-5,6-dihydro-2H-thiopyran VI. The same mixture is obtained by reduction of either 4-dimethylamino-3,5,6-trimethoxycarbonyl-3,4-dihydro-2H-thiopyran II or 3,5,6-trimethoxycarbonyl-2H-thiopyran III. Intermediate formation of a delocalised carbanion is postulated in order to explain these results.

Synthesis and electrochemistry of new mixed polyfluorenylidenes with low gap between their oxidation and reduction potentials

An electrochemical oxidation of a mixture of two fluorenylidenes bearing respectively a donor and an acceptor unit is described. The electrochemical study of the new materials shows that they possess a low gap between their oxidation and reduction potentials.

Anodic behaviour of methylidene-cyclopentadiaryl derivatives: cyclic voltammetry and theoretical study

Electrochemical behaviour of a functionalized fluorenylidene 1 is studied in comparison with a cyclopentadithiophene analogue 2. The influence of the main aromatic group on the electropolymerization ability is reported. We demonstrated that the lack of sulfur atoms in the monomer structure leads to an absence of polymerization due to the spin density located on the methylidene bridge in the radical cation. From modelling considerations, we have evaluated the participation of the methylidene bridge in the p-doping process. The good correlation between the p-doping level and the partial atomic charge carried by the methylidene bridge for poly(2) and poly(3) indicates that an extension of the conjugated area improves the p-doping level when the side chain is electronically connected to the main chain of polymer.