Model compound studies of small bandgap conjugated poly(heteroarylene methines)

Abstract

Quinoid thiophene oligomers 6, 7, and 8 were prepared and characterized as model compounds of small bandgap polymers and were shown to have solid state bandgaps in the range of 1.31-2.15 eV and a lowest energy solution optical absorption maximum (λ max ) of 480-676 nm. It was found that the bandgap and ionization potential decrease and electron affinity increases with increasing size of the quinoid oligomer. These results of the model compound studies are in agreement with theoretical predictions for the electronic properties of polythiophene with quinoid geometry and suggest that small bandgap polymers can be achieved by direct incorporation of quinoid structure in the polymer backbone.