Optical properties of pyrrolyl-substituted polysilanes

Pyrrolyl-substituted polysilanes were synthesized in the present study. The pyrrolyl rings directly attached to the Si conjugated main chains with Si- N bonds. Poly(alkylpyrrolylsilane) and poly(phenylpyrrolylsilane) showed a chromophore which is attributed to sigma-sigma* transition in the conjugate d system associated with near-UV fluorescence. However, a strong photolumin escence band was observed at 450-500 mn other than the near-UV photolumines cence for the polysilanes. The luminescence is due to the energy relaxation from sigma* to an inter-band level produced by sigma-pi mixing between mai n chain sigma-conjugated system and pyrrolyl groups as suggested by theoret ical calculations. Transient spectroscopy of the polysilanes was also carri ed out showing a new chromophore at the vis-IR region (800 nm) other than n ear-UV (300-400 nm) and IR (similar to 2000 nm) absorption bands typically observed for alkyl- and phenyl-substituted polysilanes. It also supports th e presence of the mid-gap level in the pyrrolyl-substituted polysilanes. (C ) 2000 Elsevier Science S.A. All rights reserved.