Electrochemical quartz crystal microbalance study of magnesium porphine electropolymerization process

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ORIGINAL PAPER

Electrochemical quartz crystal microbalance study of magnesium porphine electropolymerization process O. I. Istakova 1 & D. V. Konev 1 & O. A. Goncharova 2 & A. E. Antipov 1,3 & C. H. Devillers 4 & M. A. Vorotyntsev 1,2,4,5 Received: 10 May 2020 / Revised: 5 August 2020 / Accepted: 6 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract Material and charge balances in the course of the electropolymerization process of the non-substituted Mg(II) porphine (MgP) at a low oxidation potential from its acetonitrile solutions of various concentrations have been studied via the in situ electrochemical quartz crystal microbalance method (EQCM). Thus, registered electrode mass increase due to the MgP oxidation at its surface has been used, in combination with in situ spectroelectrochemical data, for determination of the key parameters of the polymerization process and of the magnesium polyporphine films deposited on the electrode surface: current efficiency of the film deposition process, average charge spent for transformation of a monomer molecule into monomer unit inside the film, number of monomer units inside the deposited film, average number of valence bonds per one monomer unit inside the film. Besides, the EQCM method applied to the discharge process of the electropolymerized film has allowed us to estimate the average charging (oxidation) degree of the monomer unit inside the film at the polymerization potential and the degree of the solvent participation in the course of the polymer’s redox transitions. It has been established that the number of bonds between porphine units is within the range of 2.2 to 2.4, with its slight increase for films deposited at higher monomer concentrations. Conclusions on the structure of polyporphine chains have been made. Keywords Electropolymerization . Redox-equivalent . Magnesium porphine . Conducting polymer . Polymer-modified electrodes

Introduction Electroactive polymeric materials and modifying coatings on their basis represent an object of numerous studies in view of their applications for sensors, electrocatalysis, power sources,

photoelectric transformation, OLED, etc. Important information on such electroactive polymers and polymer-containing composites is provided by the technique of electrochemical quartz crystal microbalance (EQCM) which may be applied under in situ electrochemical conditions. This method has

Dedicated to our esteemed friend and colleague, Prof. Dr. Fritz Scholtz, at the occasion of his 65th birthday. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04800-1) contains supplementary material, which is available to authorized users. * D. V. Konev [email protected]

2

Lomonosov Moscow State University, Moscow, Russia

3

Mendeleev University of Chemical Technology of Russia, Moscow, Russia

4

ICMUB, UMR 6302 CNRS-Université de Bourgogne-Franche-Comté, Dijon, France

5

Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy o