52
3 Technetium Coordinated by Inorganic Ligands in Aqueous …
Fig. 3.10 Cyclic
voltammograms resulting
from reduction of TcO 4
− .
Conditions: 25 °C; [OH − ] =
0.12 M;
TcO
−
4
= 1 ÷
7·10 −3 M; nitrogen saturated
solution; hanging mercury
drop electrode, surface area
= 9.4 × 10 −3 cm 2 . Curves
(A), (B), and (C) result from
scan rates of 1, 20, and
100 V·s −1 , respectively
(reprinted with permission
from Deutsch et al. (1978)
Copyright 1978 American
Chemical Society)
Astheimer et al. and Schwochau et al. (Astheimer and Schwochau 1976;
Schwochau et al. 1974) pointed out that TcO
2−
4 ions are extremely sensitive to the
presence of oxygen and atmospheric moisture. Under such conditions, the Tc(VI))
undergoes oxidation and disproportionation reactions. These researchers investigated
the process of TcO
−
4 ion reduction in acetonitrile with (CH 3 ) 4 NClO 4 as a supporting
electrolyte. The half-wave potential for a one-electrode Tc(VII)/Tc(VI) redox couple
was found to be equal to E 1/2 = −1.74 V versus SCE.