ELECTROPOLYMERIZATION OF BIS(2-CYANO-2-ALPHA-THIENYLETHENYL)ARYLENES

The synthesis and the electrochemical studies of 1,3-bis(2-cyano-2-alp ha-thienylethenyl)benzene (1), 1,4-bis(2-cyano-2-alpha-thienylethenyl) benzene (2), and 2,7-bis(2-cyano-2-alpha-thienylethenyl)biphenylene (3 ) are reported herein. While compound 2 could be reversibly reduced to form the corresponding dianion, compounds I and 3 show irreversible o r quasireversible reductions in their cyclic voltammetric studies. We tentatively attribute the high reactivity of the dianions of 1 and 3 t o their diradicaloid behavior. This explanation is further supported b y PM3/RHF-PM3/UHF calculations. Compounds 1-3 could be irreversibly ox idized at the potential more positive than +1.3 V. Among these compoun ds, 3 shows the highest reactivity toward oxidative electropolymerizat ion. The resulting polymer film is relatively stable and electroactive . Although polymeric films of compounds 1 and 2 could be formed at hig her monomer concentrations, the films are unstable toward electrochemi cal oxidation. UV-vis analyses of the polymeric films reveal that elec tropolymerization of 2 is quenched at the early stage of the polymeriz ation, resulting in significant amounts of oligomers in the matrix. Ho wever, biphenylene containing monomer 3 could be smoothly converted to highly conjugated polymers under electrochemical oxidation.