| Abstract
| - The amavadine complex and its model[VL2]2- (L =-ON[CH(CH3)COO-]2(HIDPA3-) or-ON(CH2COO-)2(HIDA3-), respectively) undergo, in aqueousmedium and at a Pt electrode, a fully electrochemical andchemicalreversible Viv/v oxidation and act as electron-transfermediators in the electrocatalytic oxidation of some thiols(HSR)such as HS(CH2)nCOOH(n = 1 or 2, i.e, mercaptoacetic ormercaptopropionic acid, respectively) andHSCH2CH(NH2)COOH (cysteine) to the corresponding disulfides(RS-SR) which were isolated upon bulk preparativeelectrolyses.As shown by digital simulation of cyclic voltammetry, this redoxcatalysis process occurs through an unprecedentedmechanism involving Michaelis−Menten type kinetics with formation(k1 = 1.2 × 103M-1 s-1) of anintermediatespecies (with half-life time of ca. 0.3 s) derived fromthe interaction of the oxidized vanadium complex (theactiveform of the mediator) with the substrate. A possible biologicalrole for amavadine is suggested by theseresults.
|
