End-capped oligothiophenes: a solid-state vibrational-spectroscopic study

Summary form only given. The experimental study of oligothiophenes offers the possibility to investigate model compounds for polythiophene with a defined chain length. Oligorners are free of mislinkages and defects which are introduced into polythiophene by the chemical or electrochemical polymerization process. Upon oxidation of unsubstituted oligothiophenes - especially short ones - there always remains the possibility, of polymerization at the terminal thiophene units. To prevent further polymerization during oxidation, several research groups investigated oligothiophenes substituted at the terminal thiophene units: methyl-substitutents at the terminal /spl alpha/-positions as well as cyclohexene units condensed to the terminal thiophene rings. We studied thiophene oligomers with cyclohexene units at the terminal thiophene units (end-capped oligothiophenes) in their neutral state with FTIR- and FT-Raman spectroscopy. Furthermore we present results on the oxidation of end-capped oligothiophenes with iodine vapor studied with in situ FTIR-spectroscopy using the ATR technique.