Kinetics of radical dimerization. Simple evaluation of rate constant from convolution voltammetry and faradaic phase angle data

Year: 2019

Authors: Pospíšil L., Hromadová M., Sokolová R., Lanza C.

Autors Affiliation: Czech Acad Sci, J Heyrovsky Inst Phys Chem, Dolejskova 3, Prague 8, Czech Republic; Czech Acad Sci, Inst Organ Chem & Biochem, Flemingovo Nam 2, Prague 6, Czech Republic; CNR Pisa, Natl Inst Opt, Via Moruzzi 1, Pisa, Italy.

Abstract: Search for possible ways of the binary information storage evoked an interest in the mechanism of the electrochemical monomer/dimer switching. Thus, determination of the rate of radical-to-dimer conversion became an issue. Mathematical formulation describing the electrochemical generation of a radical followed by a bimolecular chemical reaction contains a quadratic term, in which case the inverse Laplace transformation does not exist. Until now, kinetic data were obtained by using finite difference simulations. We report an alternative and simpler evaluation method, which uses the frequency dependence of the faradaic impedance. Determination of the required surface concentration uses convoluted voltammogram recorded at the same bulk concentration as the impedance data. Functional dependence of the faradaic phase angle on frequency (cot phi vs. omega(1/2)) shows a maximum at lower frequencies containing information on the dimerization kinetics and a linear asymptote at the highest frequency range yields the electron transfer rate. This new procedure was applied to four different known redox systems, all involving radical dimerization process.

Journal/Review: ELECTROCHIMICA ACTA

Volume: 300      Pages from: 284  to: 289

More Information: This research was supported by The Czech Academy of Sciences (RVO: 61388963 , 61388955 ) and the Czech Science Foundation ( 18-04682S ). We acknowledge the preparation of compounds by M. J. Fuchter (Department of Chemistry, Imperial College London), by J. Plutnar and F. Teplý (Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague). Authors are indebted to Dr. N. Fanelli of CNR Pisa for his valuable help in the development of the software code. Appendix A
KeyWords: Eis, Convolution voltammetry, Rate constants, Dimerization, Fitting
DOI: 10.1016/j.electacta.2019.01.119

Citations: 3
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