We report electrochemical studies on the influence of a small concentration of chloride ions on the electroactivity of the polymer matrix of polypyrrole (PPy), poly(
N-methylpyrrole) [p(N-MePy)] and a poly(titanocene-propyl-pyrrole) derivative, p(Tc3Py) [Tc(CH
2)
3NC
4H
4; Tc=CpCpTiCl
2; Cp=C
5H
5; Cp=C
5H
4] in acetonitrile (AN), tetrahydrofuran (THF) and
N,
N-dimethylformamide (DMF). The polymer films were obtained on Pt disc electrodes from AN solutions of the monomers containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF
6) as the supporting electrolyte and then transferred to the corresponding monomer-free solution. Studies in Cl
–-containing solutions have shown that the p(Tc3Py) matrix is very sensitive to the presence of Cl
– ions in all the above solvents, namely that it was subjected to electrochemical degradation at potentials above 0.1 V vs. a Ag/0.01 M Ag
+ in AN reference electrode. Degradation of the p(Tc3Py) matrix was also observed in chloride-free DMF+TBAPF
6 solutions. Addition of chloride ions to the AN solution containing pyrrole,
N-methylpyrrole or Tc3Py inhibits the deposition of the polymer films. On the other hand, we have found that PPy and p(N-MePy) matrices after their deposition in chloride-free AN solutions show much more stable redox responses in contact with chloride and/or DMF solutions. Possible mechanisms of these effects are discussed.Abbreviations AN
acetonitrile
- Cp
cyclopentadienyl
- DMF
N,
N-dimethylformamide
- N-MePy
N-methylpyrrole
- p(N-MePy)
poly(
N-methylpyrrole)
- PPy
polypyrrole
- p(Tc3Py)
poly[Tc(CH
2)
3NC
4H
4]
- Py
pyrrole
- Tc
titanocene=bis(cyclopentadienyl)titanium dichloride, Cp
2TiCl
2, or its radical CpCpTiCl
2 (Cp=C
5H
4)
- Tc3Py
titanocene-propyl-pyrrole, Tc(CH
2)
3NC
4H
4
- THF
tetrahydrofuran
Contribution to the 3rd Baltic Conference on Electrochemistry, Gdansk-Sobieszewo, Poland, 23–26 April 2003Dedicated to the memory of Harry B. Mark, Jr. (28 February 1934–3 March 2003)
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