Abstract:
Electrochemical syntheses of conducting polythiophenes and polypyrroles
received considerable attention. Unlike pyrrole based polymers, some
3-substituted polythiophene derivatives dissolve in common organic
solvents. There are reports on preparation of 3-substituted polythiophene
films and their applications such as field-effect transistors, chemical and
biochemical sensors. 3-Substituted polythiophenes with long pendent redox
groups in the polymer backbone act as electron transfer mediators.
Electrodes modified with poly (pyrrole-anthraquinone) films catalyze the
reduction of dioxygen. Therefore, it is of interest to examine the behaviour
of its polythiophene analogue. In this communication, we report the
synthesis of the monomer (5) and electrochemical behaviour of (5) and the
resulting polymer, poly(5).
Perkin reaction of thiophene-3-carboxaldehyde with malonic acid gave 3-
(3-thienyl) acrylic acid (1). Reduction of (1) with Na/Hg yielded 3-(3-
thienyl) propionic acid (2). Further reduction of (2) with LiAlH4 afforded
the alcohol (3) as colourless oil. The acid chloride (4) was prepared by
reacting 9,10-anthraquinone-2-carboxylic acid with thionyl chloride. The
monomer (5) was obtained in good yield by reacting (3) with (4). Cyclic
voltammetry of (5) showed two reversible peaks at Eo = –0.80 and –1.36 V.
The electrochemical behaviour of poly(5) has been examined. These films
were quite stable to repetitive scanning between 0 and –1.35 V. The neutral,
hydrophobic poly(5) films show some resistance to swelling in acetonitrile
media.
