Electrochemical reduction of 1,4-benzoquinone.: Interaction with alkylated thymine and adenine nucleobases

The electrochemical reduction of 1,4-benzoquinone (Q) in the presence of 1-octylthymine and 9-octyladenine has been performed in dimethylsulfoxide on glassy carbon electrodes. The electrochemical behaviour shows that the semiquinone (Q(.-)) and the quinone dianion (Q(2-)) interact with 1-octylthymine (TH) following a mechanism which involves association and protonation reactions. It is demonstrated by cyclic voltammetry and NMR experiments, that the protonated dianion (QH(-)) is stabilised by an excess of TH, alternatively it disproportionates into an association complex of dianion-hydroquinone [Q,QH(2)](2-). The 1-octylthymine anion (T-) produced in the proton transfer reactions activates a homogeneous chain mechanism allowing the consumption of benzoquinone. For the experiments carried out in the presence of 9-octyladenine (AH), it was observed that only a strong hydrogen bonding association takes place between the nucleobase and Q(2-). (C) 2003 Elsevier Science B.V. All rights reserved.