Theoretical characterization of the electronic properties of extended thienylenevinylene oligomers

TL;DR

This paper combines semiempirical and ab initio calculations to analyze the electronic properties of thienylenevinylene oligomers, revealing their potential for electronic applications due to extensive pi-electron delocalization.

Contribution

It introduces a simple model linking the band structure of polymers to oligomer electronic states, validated by calculations and experiments.

Findings

The gap varies with oligomer size and matches experimental data.

Torsion angles up to 30° have minimal impact on electronic properties.

Oligomers exhibit extensive pi-electron delocalization along the backbone.

Abstract

We present semiempirical tight binding calculations on thienylenevinylene oligomers up to the hexadecamer stage (n=16) and ab initio calculations based on the local density approximation up to n=8. The results correctly describe the experimental variations of the gap versus size, the optical spectra, and the electrochemical redox potentials. We propose a simple model to deduce 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 function of the torsion angle between consecutive cells: the modifications are found to be small up to a ~30^{\circ}; angle. We show that these oligomers possess extensive pi-electron delocalization along the molecular backbone which makes them interesting for future electronic applications such as molecular wires.