Theoretical characterization of the electronic properties of extended thienylenevinylene oligomers

We present semiempirical tight binding calculations on thienylenevinylene o ligomers up to the hexadecamer stage (n=16) and ab initio calculations base d on the local density approximation up to n=8. The results correctly descr ibe the experimental variations of the gap versus size, the optical spectra , and the electrochemical redox potentials. We propose a simple model to de duce from the band structure of the polymer chain the electronic states of the oligomers close to the gap. We analyze the evolution of the gap as a fu nction of the torsion angle between consecutive cells: the modifications ar e found to be small up to a similar to 30 degrees angle. We show that these oligomers possess extensive pi-electron delocalization along the molecular backbone which makes them interesting for future electronic applications s uch as molecular wires. (C) 1999 American Institute of Physics. [S0021-9606 (99)31937-1].