Influence of substituents and length of silanylene units on the electronic structure of pi-conjugated polymeric organosilicon systems

The electronic structure of several silicon- and germanium-containing pi-conjugated linear chain polymers was studied using extended Huckel tight-binding calculations. Emphasis has been put on the effects of the electronic structure of model compounds -[(ER2)x-CHR] (n)- varying: (1) the pi system CHR (chromophore); (2) substituents on silicon and germanium atoms; (3) the inorganic atom E (Si and Gel; (4) the number x of silanylene units. The results indicate in all cases a sigma HOCO because of the delocalized interaction along the polymer skeleton and a pi* LUCO caused by an antibonding interaction localized on the chromophore.