Theoretical conformational study of poly(trans-1, 2-di(2-thienyl) ethylene):: Effects on the electronic structure and optical properties

In the present study, we investigate the monomer ethylene-bridged-bithiophene (TET) and the dimer ethylene-bridged-bithiophene (TET), to find the more probable conformations of the oligomer and their electronic properties. Geometrical optimizations were carried out at semiempirical level using the Austin method one (AM1) and parametric method 3 (PM3). The electronic transition energies and their associated oscillator strength values are calculated for neutral oligomers. The calculations are conducted using the intermediate neglect of differential overlap Hamiltonian (INDO) in combination with a single configuration-interaction technique in order to include correlation effects. We also employ the negative factor counting (NFC) technique to obtain the electronic density of states (DOS). (C) 2006 Wiley Periodicals, Inc.