Influence of Mixed 6-Thioguanine-Nonionic Surfactant Adsorption Layers on Kinetics and Mechanism of Bi(III) Ion Electroreduction

Abstract

The presence of mixed 6-thioguanine-nonionic surfactant adsorption layers affects the mechanism and kinetics of the irreversible Bi(III) ion electroreduction process in chlorates(VII). Tween 80 and Triton X-100 change the dynamics of the catalytic effects of 6-thioguanine on Bi(III) ion electroreduction with the tendency of inhibition. The mechanism of catalytic activity of 6thioguanine is associated with formation of complexes under specific conditions which exist on the electrode surface. The effects of both 6TG and suitable surfactant mixture on the first electron transfer are much greater than those on the transition of other electrons. The Bi-6TG type complex plays the main role in the Bi-6-thioguanine-Tween 80 or Bi-6-thioguanine-Triton X-100 systems, as 6-thioguanine dominates in the formation of adsorption equilibria of the studied mixtures.

Temperature influence on the electrode process in the presence of 6-thioguanine and surfactants

“…The surfactants presence changes evidently the properties of the studied solution. Moreover, the previous studies proved that Triton X-100 and Tween 80 change the dynamics of the catalytic activity of thiopurine drugs on Bi(III) ions electroreduction with the tendency of inhibition (Kaliszczak and Nosal-Wiercińska, 2018;Kaliszczak and Nosal-Wiercińska, 2019;Kaliszczak and Nosal-Wiercińska, 2020). Table 1.…”

Electroreduction of Bi(III) Ions in the Aspect of Expanding the ”Cap – Pair” Effect

“…The introduction of thiopurine derivatives (6-mercaptopurine, 6-thioguanine, azathioprine) to solutions of Bi(III) ions in 2 mol·dm -3 chlorates(VII) indicates an increase in the reversibility of Bi(III) electroreduction [31] (an increase in the SWV peak current for Bi(III) ion electroreduction as well as a simultaneous reduction in the width of SWV peaks at half their height [42][43][44]). The effect of the studied surfactants (Tween 80 and Triton X -100) on the figure of the SWV peaks Bi(III) ions electroreduction in 2 moldm -3 chlorates(VII) at a constant concentration of accelerating substance (1•10 -3 mol•dm -3 6TG, 6MP, AZA) depends on a change in the electrode process reversibility towards inhibition [42][43][44].…”

“…The addition of surfactants to such a system affects ∆Ea-c increase. There is a change in the dynamics of the catalytic action of thiopurine derivatives [42][43][44].…”

“…However, changes in the mechanism of the Bi(III) ion electroreduction process in the presence of a mixture of thiopurine derivatives and surfactants in the base electrolyte solution were associated with the blocking of the electrode's surface by surfactants, which pushes the previously formed active complexes of Bi -thiopurine from the adsorption layer. The main role of Bi -thiopurine complexes has been indicated [42][43][44].…”

“…The kinetic parameter ks determined by using of electrochemical techniques indicating the catalytic effect of thiopurine derivatives and changes in its magnitude in connection with the presence of 6TG -TritonX-100 and 6TG -Tween 80, 6MP -TritonX-100 and 6MP -Tween 80 or AZA -TritonX-100 and AZA -Tween 80 mixtures (Figures 3a, b) [42][43][44]. a…”