3-methylthiophene/ perchlorate

Fig. 13. ATR-FTIR spectra recorded during the oxidation of a 3-methylthiophene polymer in contact with an electrolyte solution containing tetrabutylammonium perchlorate. The spectrum numbers correspond to the numbers in Fig. 15. The spectra are smoothed but not baseline corrected. The spectrum of the electrolyte solution was subtracted.

Synthesis from Pyrylium and Nitrllium Salts. Russian workers31,59 have found that acetonylthiophenes yield pyrylium salts when allowed to react with anhydrides in the presence of 70% perchloric acid, and that these salts are converted into thienopyridines by treatment with ethanolic ammonia. For example 4-acetonyl-2-methylthiophene and acetic anhydride gave 2,5,7-trimethylthieno[2,3-c)pyrylium perchlorate (33), from which 2,5,7-trimethylthieno[2,3-c]pyridine (34) was obtained. 

Fig.3. Complex-plane photoimpedance spectrum of poly-3-methylthiophene in acetonitrile (0.1 M tetrabutylammonium perchlorate). Absorbance response is recorded at 510 nm and 0.800 V with 0.1 V excitation amplitude. 

P. A. Christensen, A. Hamnett and S. J. Higgins, In situ FTIR study of charge conduction in a poly(3-methylthiophene)-poly( 1 -[2-(3-thienyl)ethyl]-l, 4,8,11 -tetraazacyclotetradecane nickel(II) perchlorate) copolymer film, J. Chem. Soc., Faraday Trans., 92, 773-781 (1996). 

A number of approaches have been proven effective, in some cases, a judicious choice of electrolyte or current density is sufficient For example, within a limited current density window, it is possible to electropolymmze aniline in neutral aqueous solution. (3). Poly-3-methylthiophene can be deposited from highly acidic aqueous solution if a stable suspension is achieved before electropolymerization (4), or as d cribed in chapto 3 of this volume, from sodium dodecyl sulfrte micelles in a less harsh medium. Micelles have also proven useful where addition of non-ionic sur ctants to the monomer solution have been employed in the preparation of poly(3,4-ethylene dioxythiophene) (PEDOT) from aqueous perchlorate solutions (5). 

FIGURE 4 In situ conductivity of electrodepositated (a) PP in CH,CN + O.l M tetraethyl-ammonium tosylate and (b) poly(3-methylthiophene) in CH CN + 0.1 M tetrabutylammo-nium perchlorate. Cyclic voltammograms are shown for comparison. 

Neither copper perchlorate nor ferric perchlorate reacts with thiophene to yield a conducting polymer. However, electrically conductive polymers are synthesized by the reaction of 3-methylthiophene or bithiophene with ferric perchlorate. With copper perchlorate, only bithiophene undergoes a simultaneous polymerization and oxidation reaction. X-ray photoelectron spectroscopy of the PT derivatives with perchlorate as counter ion indicates that a significant amount of the chlorine may be covalently bonded to the polymer [288, 574], The electrical conductivity of polymerized bithiophene reaches values as high as 4.5 S cm [574]. 3-Dodecyl-2,2 -bithiophene, 3-(3-phenylpropyl)thiopheneand 3,4-dibutoxythiophene can be polymerized oxidatively using either copper perchlorate, copper tetrafluoroborate, or ferric perchlorate [575]. 

Py pyrrole, MPy 1-methylpyrrole, PPy polypyrrole, PMPy poly(l-methylpyrrole), EDOT 3,4-ethylenedioxytiophene, PEDOT poly(3,4-ethylenedioxytiophene), MT 3-methylthiophene, PMT poly(3-methylthiopliene), NaPSS sodium polystyrene sulfonate, NaDBS sodium dodecylbenzenesulfonate, NaPTS sodium para-toluene sulfonate, BSA benzenesulfonic acid, SSA 2-hydroxy-5-sulfobenzoic acid, MES 2-(Af-morpholino) ethanesulfonic acid, MOPS 3-(Al-morpholino) propanesulfonic acid, PIPES piperazine-l,4-bis(2-ethanesulfonic) acid, MeCN acetonitrile, DCE 1,2-dichloroetane, BU4NPF6 tetrabutylammonium hexafluor-ophosphate, BTPPA-CIO4 bis(triphenylphosphoranylidene)ammonium perchlorate, BTPPA-TFPB bis(triphenylphosphoranylidene)ammonium tetrakis[3,5-bis (trifluoromethyl)phenyl]borate, TPenA tetraphenylammonium... 

These studies have indicated that (i) polyacetylene can act as a catalytic electrode in an aqueous electrolyte for the reduction of gaseous oxygen, hydrogen peroxide or perchloric acid and (ii) poly-3-methylthiophene can act as the catalytic electrode for the reduction of SO in Li(S02)2AlCl and permit the cathode discharge product to become rapidly oxidized without resorting to use of chlorine as an intermediate. 

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