Electrosynthesis, spectral and structural studies of a semi-conducting oligomer deriving from a methoxy-substituted chalcone

The anodic oxidation of a substituted chalcone namely the (E)-1-(4-methoxyphenyI)-3-(3,4,5-trimethoxyphenyl) prop-2-enone (TMC) was investigated by different electrochemical techniques using a platinum working electrode in acetonitrile. On the cyclic voltammetry time scale, the TMC exhibited a single irreversible anodic peak around 1.4 V vs. Ag/AgC1 and the coupling of the radical cations, issued from the first electron transfer, was the governing reaction near the electrode. Electrolysis at a constant potential revealed that an oligo o-phenylenevinylene was the main product of the anodic oxidation of TMC. The chemical structure of the isolated oligomer was elucidated by H-1, C-13 NMR, and IR spectros-copy. Gel permeation chromatography indicated that the average chain length was about 5 units. In addition, the obtained oligomer was thermally stable up to 220 degrees C and exhibited a light emission in the indigo-blue region. Finally, a mechanism for the TMC electro-oligomerization was proposed on the basis of the electrochemical data and the theoretical calculation of the spin densities distribution for the TMC radical cation. (C) 2016 Elsevier B.V. All rights reserved.