Redox reactions in a linear polyviologen derivative studied by in situ ESR/UV-vis-NIR spectroelectrochemistry
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It is well-known that reductive electropolymerization of cyanopyridinium moieties yields to viologenic materials. In this work, a monomer with two electropolymerizable cyanopyridinium groups separated by a six carbon spacer (CNP) has been synthesized. Its electropolymerization in aqueous electrolyte results in a linear polyviologen (PV) derivative, a purple-colored film deposited on the electrode surface. Cyclic voltammetry (CV) of PV films displays two well-resolved one-electron redox processes at c.a. −0.5 and −1.0 V vs. Ag/AgCl. Fourier transform infrared (FTIR) spectral analysis shows successful polymerization of PV from the CNP monomer. In situ electron spin resonance (ESR)/UV-vis-NIR spectroelectrochemistry was used in order to simultaneously determine the polycation radical as well as the magnetic and optical response of the redox PV system. The single-line ESR spectrum observed at the first reduction peak of PV film was assigned to the formation of stable viologen cation radical species within the polymer matrix, exhibiting the characteristic UV-vis-NIR viologen cation radical absorption bands. The electrosynthesized linear PV system represents a promising stable redox active n-type material for organic rechargeable devices.
KeywordsCyanopyridine Polyviologen derivative Reductive electropolymerization In situ ESR/UV-vis-NIR spectroelectrochemistry n-type materials
We gratefully acknowledge the financial support from Academy of Finland. BG would like to thank the Center of Spectroelectrochemistry, IFW Dresden for providing research facilities. BG also would like to thank Frank Ziegs for the technical support and fruitful discussions.
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