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 Si's delocalized σ electrons and Pyr (Thi) localized π electrons. In the valence band states, N's (S's) non-bonding (n) π electrons localizing at Pyr and Thi groups splits the PSi's 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.