Electronic structure of π-conjugated arylene ethynylene polymers

We investigate theoretically the geometric and electronic structure of π-conjugated poly(arylene ethynylene) polymers: (C≡C-Ar-C≡CAr′-)_n, where Ar and Ar′ correspond to a pyridinylene or a phenylene and a thienylene moiety, respectively. It was recently observed that these polymers present a large third-harmonic-generation response as well as strong photoluminescence; the latter feature indicates that they are potentially good candidates as active materials in electroluminescent devices. Geometry optimizations are carried out at the AM1 level, whereas the electronic properties are derived from valence-effective Hamiltonian calculations. We also simulate the whole UV-Vis optical absorption spectra of the oligomers on the basis of an INDO configuration interaction approach.