Synthesis and Characterization of Some Three Dimensional Cyclic Organosilanes

点击翻译按钮获取中文摘要

The emission from the porous silicon has not fully explained yet. Here, in order to take one of possible chemical approaches to clarify the essential structure of the emission of this kind, we have planned to synthesize and characterize some caged solid organosilanes having both silicon-silicon and silicon-oxygen-silicon bonds. Tow types of tetrameric caged polysiloxanes containing silicon-silicon bonds have been prepared by condensation of 1,2- dimethyl-1,1,2,2-tetraethoxy disilane under acidic conditions. They show UV absorption maxima at 235 and 229 nm, respectively. At the same time, they emit as expected at 360 and 351 nm with quantum yields of 0.13 and O.11 respectively. These emissive properties are comp ared with those of two-dimensional analogues and this indicates that such a rigid three-dimensional structure having both silicon-silicon and silicon-oxy gen-silicon bonds should be essential for the efficient emission observed. Then, to examine the substituent effect on the emission, we have prepared the same types of caged polysiloxane with isopropyl groups instead of methyl groups by condensation of 1,2-diisopropyl-1,1,2,2- tetraethoxy disilane under similar acidic conditions. They show UV absorptions at longer wavelength, 256 and 242 nm, respectively, and give the emission maxima at 361 and 350 nm, respectively, with poor quantum efficiency, namely, 0.067 and 0.034, respectively. Phenyl derivatives have been also prepared starting from hydrolysis of 1,2-diphenyl-1,1,2,2- tetrachlorodisilane in aqueous acetone.