Syntheses and electropolymerization behavior of ethylenedioxythiophene-substituted silanes M’hamed Chahma and Robin G. Hicks Abstract: Silicon-bridged thiophene oligomers have been prepared via the reactions of lithiated (3,4-ethylenedioxy)thio- phene (EDOT) (1) or 2,2′-bis-(3,4-ethylenedioxy)thiophene (biEDOT) (2) with dichlorodimethylsilane to afford bis-(2,3- dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-dimethylsilane (3) and dimethyl-bis-(2,3,2′ ,3′ -tetrahydro-[5,5′ ]bi[thieno[3,4-b] [1,4]dioxinyl]-7-yl)silane (4). Products 3 and 4 were characterized and show good stability in organic solvent and in air. The electropolymerization of these monomers affords stable and highly conducting polymers. The conductivity was found to be 25 and 60 S/cm for Poly3 and Poly4, respectively. Characterization data for the polymers suggested that the resulting materials have a backbone identical to p(EDOT), which formed through cleavage of the silicon–carbon (Si—C) bonds during electropolymerization. Key words: polythiophenes, EDOT, silicon, electropolymerization, Si—C bond cleavage, conductivity. Résumé : Faisant appel à des réactions de (3,4-éthylènedioxy)thiophène (EDOT) (1) ou de 2,2′-bis-(3,4-éthylène- dioxy)thiophène (biEDOT) avec du dichlorodiméthylsilane, on a préparé des oligomères de thiophène avec pont de silicium, les bis-(2,3-dihydro-thiéno[3,4-b][1,4]dioxin-5-yl)diméthylsilane (3) et diméthyl-bis-(2,3,2′ ,3′ -tétrahydro- [5,5′ ]bi[thiéno[3,4-b][1,4]dioxinyl]-7-yl)silane (4). Les produits 3 et 4 ont été caractérisés et présentent une bonne sta- bilité dans les solvants organiques et dans l’air. L’électropolymérisation de ces monomères conduit à des polymères sta- bles et très bons conducteurs. On a trouvé que les conductivités respectives des Poly3 et Poly4 sont de 25 et 60 S/cm. Les données de caractérisation des polymères suggèrent que les produits obtenus possèdent un squelette identique à ce- lui du p(EDOT) qui se forme par clivage des liaisons silicium–carbone (Si—C) au cours de l’électropolymérisation. Mots clés : polythiophènes, EDOT, silicium, électropolymérisation, clivage de la liaison Si—C, conductivité. [Traduit par la Rédaction] Chahma and Hicks 1633 Introduction Polythiophene and its derivatives are widely used in tran- sistors (1–3), light emitting diodes (4), electroluminescent devices (5, 6), photovoltaic cells (7), and bioelectrochemical sensors (8, 9). Despite the existence of a wide variety of thiophene monomers, the preparation of novel thiophene motifs remains a quest for many scientists as part of the search for new materials with properties such as low band gaps, electrochromism ranges, etc. One derivative of thio- phene that has become immensely popular is 3,4-ethylen- edioxy)thiophene (EDOT) (1) (10). The corresponding polymer, p(EDOT), is exceptionally stable in its doped state and highly conducting. It also exhibits a low oxidation po- tential with respect to classical polythiophene derivatives (11). Recently, Wudl and co-workers reported that p(EDOT) have promising applications in the field of “plastic electron- ics” (12, 13). Different strategies have been used to synthesize new polymers incorporating EDOT. For example, the incorpora- tion of alkyl chains in the ethylene moiety increases the sol- ubility and conductivity of the corresponding polymers (14). Another approach involves polymers consisting of alternat- ing EDOT with aryl groups (e.g., benzene, furan, carbazole) to provide a large range of redox and optical properties (15– 17). Hybrid conjugated organic EDOT – metal-containing polymers have also been explored (18, 19). Another recent approach has been the incorporation of main group ele- ments. We recently synthesized a monomer bis(3,4- ethylenedioxy-2-thienyl)sulfide in which two EDOT moi- eties are connected to a divalent sulfur atom; its correspond- ing polymer exhibits high electrochemical stability in its oxidized and reduced states and good conductivity for a nonconjugated polymer (20). Other main group elements have been introduced into conducting polymer systems, including silicon. Ferraris and co-workers (21) prepared bridged bithiophenes linked by Can. J. Chem. 82: 1629–1633 (2004) doi: 10.1139/V04-139 © 2004 NRC Canada 1629 Received 30 April 2004. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 21 December 2004. M. Chahma and R.G. Hicks. 1 Department of Chemistry, University of Victoria, PO Box 3065, STN CSC, Victoria, BC V8W 3V6, Canada. 1 Corresponding author (e-mail: rhicks@uvic.ca).