| Budget Amount *help |
¥7,100,000 (Direct Cost: ¥7,100,000)
Fiscal Year 1989: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1988: ¥6,200,000 (Direct Cost: ¥6,200,000)
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| Research Abstract |
Photolysis of cyclopolysilanes has been carried out by laser flash photolysis in methylcyclohexane (MCH) at 293K and steady-state photolysis in methylcyclohexane-isopentane (MP; 3:1, v/v) glass at 77K. The photolysis patterns are remarkably dependent on the molecular structures of cyclotetrasilanes. The planar persilylcyclotetrasilanes give rise to the corresponding disilanes with absorption peaks at 410 nm at 293K and at 415 nm at 77K. For the peralkylcyclotetrasilanes having bent structures, photolysis occurs to give the corresponding silylene and cyclotrisilane at 293K, but not in MP glass at 77K. For cyclohexasilane, photolysis occurs to give dimethylsilylene even in MP glass at 77K. These photolyses originate from the excited singlet state (S_1), judging from a rapid build-up of the transient absorption after pulsing. Transient peaks for diisopropylsilylene, t-butylmethylsilylene and dimethylsilylene are observed at 530, 515, and 470 nm with lifetimes of 38, 50, and 380 ns in MCH at 293K, respectively. The fluorescence of cyclotetrasilanes with an extremely large Stokes shift (up to 13700 cm^<-1>) has been observed in rigid glass at 77K. The photochemical and photophysical properties of cyclopolysilanes have been discussed from the viewpoints of their molecular structures.
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