Abstract:
|
Quantum chemical methods have been applied on model oligomers of poly(thiaheterohelicene)s to investigate
the structural and electronic properties of these systems. Specifically, the properties of the helical structures
found for poly(heterohelicene) and poly(methyl-sulfonium), which were calculated using density functional
theory calculations, are in good agreement with available experimental data. The geometrical parameters
obtained for poly(methyl-sulfonium) reflect the enlargement of the inner carbon-carbon bond lengths at the
thiophene rings, which are those closer to the helical screw axes, and lead to reduce their aromaticity of such
heterocycles. On this basis, a relationship between the aromaticity and the lowest π-π* transition energy has
been established. Finally, the lowest π-π* transitions have been extrapolated for infinite polymer chains of poly(heterohelicene) and poly(methyl-sulfonium) using different theoretical approaches. |