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Conformational study of silicon backbone of poly(methylphenylsilane) functionalized with pendant azobenzene groups has been carried out. The conformation of the silicon backbone depends on the molar ratio of the Si units with and without the pendant azobenzene group, and the inflection point for the conformational change from the slowly winding helix to random coil has been found to be ca. 0.5 of the molar ratio. The conformational change has been induced by the photoisomerization of pendant azobenzene groups in the film state.

The synthesis of poly(methylphenylsilane) functionalized with pendant p-nitroazobenzene groups (PMPS-azo) has been carried out, and their photophysical and photochemical processes have been studied. The fluorescence quantum yields of PMPS-azo decrease with an increase of the amounts of the pendant p-nitroazobenzene groups. The picosecond fluorescence decay kinetics of PMPS-azo was interpreted in terms of not only the energy transfer, but also the electron transfer from the Si–Si main chain to the pendant p-nitroazobenzene group. The evidence for intramolecular electron transfer was provided by the formation of the radical anion of the pendant trans-p-nitroazobenzene group upon steady-state photolysis of PMPS-azo at 77 K.

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Steady-state photolyses of 4-methoxy-4′-cyanoazobenzene and 4-methoxy-4′-nitroazobenzene have been studied in rigid matrices. The radical anions of these azobenzenes have been observed for the first time by the 266 nm and 355 nm light irradiation in 2-methyltetrahydrofuran at 77 K.