Optimal strategy based on radiation chemistry for facile and direct synthesis of poly(3-thiophene acetic acid) polymers in water and dichloromethane

In this work, synthesis of nanostructured conducting poly(3-thiophene acetic acid) (PTAA) polymers was developed by means of γ-induced oxidative polymerization of TAA monomers dissolved either in water or in dichloromethane. This synthesis was shown to be facile and directly feasible without any prior esterification of TAA and in the absence of oxidizing agents. Radiolytic yields of TAA oxidation as well as irradiation doses required for quantitative PTAA preparation were determined for each solvent. UV-Vis and ATR-FTIR spectroscopies demonstrated the successful formation of two PTAA polymers, so-called "PTAAH2O"and "PTAACH2Cl2". Size exclusion chromatography (SEC) highlighted convergent molecular weight values corresponding to approximately 13 monomer units. A similar behavior for both radio-synthesized PTAAs was monitored by thermogravimetric analysis (TGA). The morphological structures of PTAAH2O and PTAACH2Cl2 were analyzed in solution by Cryo-TEM and after deposition by SEM and AFM. Microscopic observations revealed the presence of two distinguishable nanostructures: nano-spherules of several hundreds of nanometers made of PTAAH2O and nano-granules of several tens of nanometers made of PTAACH2Cl2. Cyclic voltammetry analysis and the Tauc plot method were employed to calculate the electrical and optical band gaps. Both polymers possess similar electrical band gaps. However, PTAACH2Cl2 affords a lower optical band gap than PTAAH2O. Four-point probe measurements showed that the radio-synthesized PTAA polymers are characterized by interesting electrical properties: a higher electrical conductivity was nevertheless recorded for PTAACH2Cl2. This study highlights the powerful ability of the radiation chemistry-based methodology to lead, as a simple, versatile and reliable method, to nanostructured PTAA conducting polymers either in aqueous or organic solutions

Trapping the δ isomer of the polyoxometalate-based Keggin cluster with a tripodal ligand

We report the synthesis, structural, and electronic characterization of the theoretically predicted, but experimentally elusive δ-isomer of the Keggin polyanion. A family of δ-Keggin polyoxoanions of the general formula, (TEA)HpNaq [H2M12(XO4)O33(TEA)].rH2O where p, q, r = [2,3,8] for 1 and [4,1,4] for 2 were isolated by the reaction of tungstate(VI) and vanadium(V) with triethanolammonium ions (TEAH), acting as a tripodal ligand grafted to the surface of the cluster leading to the entrapment and stabilization of the elusive polyanhionic δ Keggin archetype. The δ-Keggin species were characterized by single-crystal X-ray diffraction, FT-IR, UV-vis, NMR and ESI-MS spectrometry. Electronic structure and structure-stability correlations were evaluated by means of DFT calculations. The compounds exhibited multi-electron transfer and reversible photochromic properties by undergoing single-crystal-to-single-crystal (SC-SC) transformations accompanied with colour changes under ligh

Synthèse, caractérisation, électrochimie et études des propriétés catalytiques de nouveaux hétéropolyanions

Dans ce travail nous avons développé des synthèses ciblées qui nous ont permis d'obtenir des composés aux propriétés électrochimiques nouvelles. Il s'agit d'hétéropolyanions dissymétriques de la série de Dawson du type [H4XW18O62]^7- (X = P ou As) et de leurs dérivés substitués. Tous ces composés nouveaux ont été caractérisés par diverses méthodes d'analyses physico-chimiques (analyse élémentaire, IR, RMN 31P et 183W, voltammétrie cyclique) qui ont démontré, sans ambages, qu'il s'agit d'échantillons d'isomères purs. Des études électrochimiques particulières concernent le comportement des composés monosubstitués, le comportement des centres métalliques électroactifs comme CU II ou le transfert d'électrons entre centres FeIII appartenant à la même molécule Dawson de type Sandwich. La diffraction des rayons X sur monocristaux a permis la détermination de structures nouvelles, telles que la structure de type "BANANE", ou des structures non encore résolues, pour ce qui est du cas de plusieurs composés Dawson de type Sandwich. Des études d'aimantation ont été menées sur ces composés qui comportent plusieurs centres métalliques. Les composés étudiés se sont avérés très efficaces dans la catalyse de la réduction des oxydes d'azote, du dioxygène ou du peroxyde d'hydrogène et dans la catalyse de l'oxydation de la coenzyme NADPH et de l'oxydation des alcènes. Ce travail se place dans le cadre du développement de nouvelles structures, voire de nouvelles propriétés, dans la chimie et l'électrochimie des hétéropolyanions. Les perspectives restent énormes et diversifiées.This work is devoted to the synthesis, characterization and electrochemistry of new dissymmetrical Dawson type heteropolyanions with the general formula [H4XW18O62]^7- (X = P or As) and their substituted derivatives. All these new compounds were characterized by various methods of physicochemical analysis (elemental analysis, IR, 31P and 183W NMR, cyclic voltammetry) which showed that pure isomer samples were obtained. Detailed electrochemical studies on the behaviour of monosubstituted species, the behaviour of the electroactive metal centres like CUII or the transfer of electrons between FeIII centres within the same sandwich Dawson molecule were carried out. X-ray diffraction on monocrystals allowed the determination of new structures, such as the "BANANA" type structure, or of not yet solved structures, of several Dawson Sandwich compounds. Magnetization studies were undertaken on these compounds which comprise several metal centres. Studied compounds proved very efficient in the catalysis of the reduction of nitrogen oxides, dioxygen or hydrogen peroxide, the catalysis of the coenzyme NADPH oxidation and the oxidation of olefin hydrocarbons. This work is part of the development program of new structures, or even of new properties in the chemistry and the electrochemistry of heteropolyanions. The prospects remain enormous and diversified.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF