A. E. Carvalho, G. B. Alcantara, Sebastião M. Oliveira
Mar 1, 2009
Citations
0
Influential Citations
13
Citations
Journal
Electrochimica Acta
Abstract
Abstract This paper reports the first study on the electrochemical reduction of lichexanthone ( 1H ) (1-hydroxy-3,6-dimethoxy-8-methylxanthen-9-one) on glassy carbon (GC) electrodes in DMSO, using cyclic voltammetry, rotating disc and ring electrodes, and long-term controlled-potential electrolysis. Parameters involving data from cyclic voltammetry and rotating disc electrodes, such as current functions, E pc1 vs. log ν , E pc2 vs. log ν , E pc/2,1 − E pc1 , − I pc1ox / I pc1red , I pc2 / I pc1 , E 1/2 vs. log ω , and collection efficiency (rotating disc and ring electrode data), were used to elucidate the reduction mechanism of 1H that involves two one-electron transfers (two reduction peaks in the voltammograms), the first of which, with reversible characteristics, involves electroreduction of 1H , producing a radical anion 1H − , whereas the second, with irreversible characteristics, involves electroreduction of 1H − , producing a dianion 1H 2− . Both transfers appear to involve an E r C slow -type mechanism with a chemical step consisting of breakage of a bond followed by protonation of residual water, or parent compound, or solvent, etc., to yield 2-hydroxy-4-methoxy-6-methylphenyl 2-hydroxy-4-methoxyphenyl ketone ( 1H 3 ), directly, in the case of 1H 2− involved. Compound 1H 3 was elucidated by 1D- and 2D-NMR methods. D 0 = 2.66 × 10 −6 cm 2 s −1 was found for the electrochemical reduction of 1H .