Syntheses Of3,4-Ethylenedioxythiophene-Tetrathiafulvalene Assemblies And Polymers

3,4-ethylenedioxythiophene (EDOT) as an important building block to design functional organic materials and polymers has received tremendous interest in recent years. The combination of an especially low oxidation potential and a relatively low band gap gives EDOT some unique electrochemical and spectroscopic properties. On the other hand, tetrathiafulvalene (TTF) derivatives are well known as strong electron donors and they can be oxidized and reduced reversibly. With this unique feature, TTF derivatives have been widely employed in numerous fields. The present theme focuses on the assembly of the two functional molecules as well as research of the spectral and electrochemical properties of EDOT-TTF based polymers.3,4-hydroxymethyl-ethylenedioxythiophene (EDTM) was synthesized from dimethyl3,4-dioxylthiophene-2,5-dicarboxylate in an improved "Five Step Synthesis" process as two isomers which are very difficult to separate in normal way, one was a six-member ring isomer bearing a hydroxymethyl group while the other was a seven-membered ring isomer bearing a secondary hydroxyl group. Both hydroxyl groups were reactive, so lauric acid and benzoic acid were reacted with EDTM by Steglich esterification to afford two EDOT derivatives, i.e., EDOT-1and EDOT-2, respectively, each was a mixture corresponding to EDTM. However, when the tetrathiafulvalene (TTF) carried carboxylic acid underwent the same reaction, only the isomer bearing hydroxymethyl group could react with it, thus we got a single product, i.e., EDOT-TTF assembly (TTF-4).Multi-steep electropolymerization was carried on on for TTF-4, EDOT-1and EDOT-2.. The results differed owing to the pendant groups. For TTF-4the deposition and desorbtion on the anode could reach equilibrium, the monomer with long alkyl as pedants (EDOT-1) could not form stable films but afford an oligomer solution, while EDOT-2could form stable films on the electrode. The conductivity of P1, P3could reach6S·cm-1,11S·cm-1by galvanostatic electropolymerization, and2.0×10-3S·cm-1,3.5×10-3S·cm-1by potentiostatic electropolymerization. The enhanced conductivity by chemical doping indicated a new way to obtain conducting polymers by increasing the conductive dimensions of the structure. Five π-conjugated poly(EDOT-ethynylene-arylene)s5-P1-5-P5were synthesized by Sonogashira reaction. The polymers with alkyl pendant (5-P4) and TTF pendant (5-P5) were soluble in commen organic solvents. The TGA results exhibited their good thermal stability. The electrochemical and spectroscopic properties were investigated by CV, UV-Vis and FL. The results indicated that there were intramolecular interaction between TTF group and polymer backbone as well as intramolecular interaction between the EDOT and fluorene moieties The fluorescence intensity of5-P5could be recovered by adding increasing amount of Fe(GlO4)3as oxidant, which implied that5-P5, as a TTF-carried polymer, performanced as fluorescence molecular switches.The conductivities of5-P4and5-P5could reach1.4x10-2S·cm-1and3.5×10-2S·cm-1after doping with I2, indicating a new way to enhance the conductivities of polymers with neutral EDOT cores.5-P5(doped with TCNQ) could form stable CT-complex with a conductivity of1.3×10-3S·cm-1,10magnitude higher than the undoped one(1.8×10-6S·cm-1). Such results indicated that the polymers with TTF pendants could afford improved conductivities after doping TTF with TCNQ as a result of.the increased conductive dimensions of the polymer backbone.