Determination of the Electronic Structure of Oligo(2-thienyl ketones) and Extrapolation to Poly(thienylene ketone)

Gas-phase ionization and attachment energy (IE and AE) values of the first few oligomers of 2-thienyl ketone have been determined experimentally. The assignments of the ultraviolet photoelectron spectra agree with the results of theoretical HF/6-31G** calculations. The constant value of the HOMO energy allows extrapolation to the corresponding polymer. A combined analysis of the AE values, the electrochemical reduction data, and the results of ab initio 6-31G** and semiempirical calculations allows one to obtain the LUMO energy for the oligomers and for an ideal gas-phase poly(thienylene ketone). The narrow valence band and the high IE value of the polymer are not propitious to p-doping. On the other hand, the high electron affinity of the oligomers and the polymer, the reversibility of the oligomer electrochemical reduction, and the large conduction band of the polymer indicate that the oligomers, and likely the polymer, could give rise to n-doped materials having high electrical conductivity.