Electronic structures of polysilanes having pyrrole and thiophene groups

The electronic structures of polysilanes (PSi) having Pyrrole (Pyr) side-chains and Thiophene (Thi) side-chains have been theoretically investigated. Two kinds of the characteristic σ–π mixing occur between Siʹs delocalized σ electrons and Pyr (Thi) localized π electrons. In the valence band states, Nʹs (Sʹs) non-bonding (n) π electrons localizing at Pyr and Thi groups splits the PSiʹs pσ band (σ–n mixing). In the band gap, two π states localized at Pyr (Thi) groups are produced (σ–π mixing). The rotation of Pyr and Thi groups varies the degree of the σ–π mixing and cause the energy dispersion toward the Si skeleton axis. This energy dispersion has a potential to change the PSi system, being a semimetallic electronic structure from a semiconducting one in the limited form.