Photofragmentation of oligosilanes and polysilanes

Alkylated and arylated oligosilanes and polysilanes, the silicon analogues of alkanes and of polyethylene, have recently attracted considerable attention (Miller and Michl, 1989). Unlike saturated hydrocarbons, these materials absorb in the near UV region. The reasons for this are related to the electropositive nature of silicon and can be understood in simple terms (Michl, 

Their excited states bear considerable similarities to those of polyenes, but also exhibit significant differences (Balaji and Michl, 1991). Upon irradiation, oligosilanes (Ishikawa and Kumada, 1986) and particularly polysilanes (Trefonas et al., 1985), readily fragment to lower-molecular-weight species, and polysilanes show promise as photoresists. 

The two silylene-generating processes are believed to occur in the singlet excited state in pericyclic fashion, while the radical-pair-forming homolytic cleavage process is believed to occur in the triplet state (Michl and Balaji, 

According to the definition given in the beginning of this section, the singlet 1,1-elimination (reductive elimination) processes qualify as fragmenta- 

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