Electrochemical synthesis and characterization of 2-amino-3-cyano-4-phenylthiophene dimer and oligomers

The electrochemical dimerization of 2-amino-3-cyano-4-phenylthiophene (ACPT) has been studied in acetonitrile solutions by using Pt electrodes. The resulting dimer obtained after a preparative electrolysis was characterized by using FAB mass, C-13 and H-1 nuclear magnetic resonance (C-13-NMR and H-1-NMR) and fourier transform infrared spectroscopic techniques. Voltammetric measurements showed that the dimer formed by the coupling of two cation radicals (CR-CR) is stable and has a reversible electrochemical behavior. The fast scan voltammetric experiments using microelectrodes revealed that the dimer formed by the coupling of a cation radical with a parent molecule (CR-PM) has a quasi-reversible electrochemistry and undergoes to further couplings resulting in oligomers. On the basis of voltammetric and spectroscopic data, it was found that dimerization of ACPT occurs mainly by the coupling of a neutral ACPT molecule with the cation radicals, which is very important in the formation of regioregular oligomers and polymers. (C) 2002 Elsevier Science Ltd. All rights reserved.