CONFORMATIONALLY INDUCED LOCALIZATION IN THE ELECTRONIC-STRUCTURE OF POLYSILANES

Ab initio electron propagator calculations with a double zeta effective core potential basis on the vertical electron binding energies of oligomeric models of polysilane chains reveal the effects of gauche conformational defects on electronic structure. When a gauche defect lies between two all-trans segments of unequal lengths, most of the probability density for the Feynman-Dyson amplitudes corresponding to the lowest ionization energy or the largest electron affinity resides on the longer segment. The energy gap between cationic and anionic states increases when a gauche defect is introduced, but the effect is larger when the defect is in the middle of the chain. These trends are explained in terms of simple bond function models suggested by examination of the Feynman-Dyson amplitudes.