Theoretical investigation of nitrogen-containing polyisothianaphthene derivatives

Summary form only given. We use a quantum chemical approach to investigate the geometric and electronic structure of aza and diaza derivatives of polyisothianaphthene (PITN). The substitution of one or two carbon atoms of the benzene ring with nitrogen atoms is intended to decrease the aromaticity of the ring, in order to affect the relative stabilities of the aromatic and quinoid forms and further reduce the polymer bandgap. Semiempirical Austin Model 1 (AM1) calculations are performed on a series of oligomers of increasing chain length, capped by various end groups which lead to either aromatic or quinoid geometric structures. The relative stabilities of these two forms are estimated on the basis of the energy per repeat unit (Epru), and the electronic properties of the aromatic and quinoid polymers are evaluated with the Valence Effective Hamiltonian (VEH) method. The synthesis of the most promising compounds, i.e., those with calculated bandgaps below 1 eV, will be presented.