Strategies towards functionalised electronically conducting organic copolymers

Here we describe the synthesis and electrochemical polymerisation of 2,5-di(2-thienyl)-3-(3-cyanopropyl)pyrrole, 2,5-di(2-thienyl)-3-(3-cyanopropyl)furan, and 3'-(3-cyanopropyl)-2,2':5',2 "-terthiophene. We report a synthetic methodology to these important conducting polymer precursor compounds that is facile, convenient and flexible. The key precursor to this study is the functionalised diketone 1,4-bis(2-thienyl)-2-(3-cyanopropyl)butane-1,4-dione. This molecule undergoes convenient ring closure to the terthiophene and dithienylpyrrole and dithienylfuran derivatives, all of which are, to our knowledge, new compounds. Importantly, this approach provides a flexible route to a range of heterocyclic polymer precursors because the cyanoalkyl functionality is grafted to the diketone before ring closure. Subsequently the nitrile group provides synthetic utility either by reduction to the amine, or hydrolysis to the carboxylic acid. The new compounds described here undergo electrochemical polymerisation leading to fixed ratio copolymers of functionalised pyrrole, thiophene and furan with thiophene itself. We describe the characterisation of these polymers using FT-IR and X-ray photoelectron spectroscopies.