Role of Active Complexes of Selected Thiopurine Derivatives …
533
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
E vs. (Ag/AgCl) /V
-10
0
10
20
I
p /µA
Bi
Ea-c = 0.102 V
Bi + 6TG
Ea-c = 0.028 V
Bi + 6MP Ea-c = 0.034 V
Bi + AZA Ea-c = 0.097 V
Fig. 5 The cyclic voltammograms of 1 : 10 −3 mol : dm −3 Bi(III) ( ) electroreduction in 2 mol : dm −3
chlorates(VII) and with 1 · 10 −3 mol : dm −3 6-mercaptopurine ( ), 1 · 10 −3 mol : dm −3 6-thioguanine
( ) 1 · 10 −3 mol : dm −3 azathioprine ( )
The increase in the value of transition coefficients, after introducing 6-thioguanine,
6-mercaptopurine, and azathioprine into the basic electrolyte solution, indicates a
significant increase in the reversibility of the Bi(III) ion electroreduction process
[38, 39]. The values of standard constant rates k s confirm the catalytic activity of
6MP, 6TG, and AZA [10, 38, 39]. Probably the size of the effect is related to the
equilibrium of the formation of the active complexes before passing more electrons
[10]. On the other hand, the addition of surfactants to the tested system indicates
the downward trend of α. This also contributes to a decrease in the value of rate