Study of Excited-State Dynamics of Organosilicon Compounds by means of Two-Step Two-Color Laser Photolysis

有机硅化合物和聚合物因其光致发光和电致发光的特性和光导电性而受到广泛关注。在本研究中，为了明确有机硅化合物的激发态性质，我们采用纳秒激光闪光光解和荧光测量的方法研究了它们在溶液中的光物理和初级光化学过程。2)为了阐明聚硅烷的结构和功能之间的关系，我们采用光照射的方法研究了聚硅烷分子在其薄膜中的取向和主链构象的控制。得到了以下结果：【结果】1)测定了9,10-二氢-9-硅菲和9-硅芴衍生物等10余种有机硅化合物的光物理参数。2)在芳香化合物中引入硅基作为取代基后，由于Si-C键的σ-电子与芳香环的π-电子的相互作用，荧光量子产率显著提高。而在硅烷取代的化合物如9,10-二氢-9-硅菲蒽和9-硅芴衍生物中，观察到荧光量子产率下降。这一观察结果可以用硅烷取代化合物的系统间交叉增强来解释。3)通过两步双色纳秒光解，9-硅芴衍生物的自由基阳离子以三态形成。自由基阳离子的去质子化形成它们的氟基自由基。4)通过9,10-二氢-9-硅菲衍生物的稳态光解反应首次合成了9-硅菲，并与菲的电子结构进行了比较。5)在拉伸聚乙烯醇薄膜上制备的聚二正二己基硅烷分子在薄膜中的分子取向存在热滞后现象。从分子相互作用的角度解释了聚二正二己基硅烷分子的取向机理。6)含对硝基偶氮苯或对氰偶氮苯悬垂基团的聚甲基苯基硅烷在光照作用下，主链的构象由螺旋变为无序螺旋。这种变化是由悬垂的偶氮苯基的光异构化引起的。【结论】利用激光闪光光解可以澄清有机硅化合物的激发态动力学，并通过光照射实现对主链信息的控制。少

Organosilicon compounds and polymers have attracted much attention because of their photo- and electro-luminescent properties and photo-conductivity. In this research, 1) in order to clarify the excited-state property of the organosilicon compounds we studied their photophysical and primary photochemical processes in solution by means of nanosecond laser flash photolysis and fluorescence measurements, and 2) to clarify the relation between the structure and function of polysilanes we studied the orientation of the polysilane molecules in their thin films, and also the control of the main chain conformation by means of photo-irradiation. The following results were obtained.【Results】1) Photophysical parameters were determined for more than ten organoslicon compounds such as 9,10-dihydro-9-silaphenanthrene and 9-silafluorene derivatives.2) Upon a silyl-group introduction to aromatic compounds as substituent(s), the fluorescence quantum yield markedly increased by the interaction between t … More he σ-electrons of a Si-C bond and π-electrons of aromatic ring. Whereas in the sila-substituted compounds such as 9,10-dihydro-9-silaphenanthrene and 9-silafluorene derivatives, the decrease in the fluorescence quantum yield was observed. This observation was explained by the enhancement of the intersystem crossing in the sila-substituted compound.3) By two-step two-color nanosecond photolysis of 9-silafluorene derivatives their radical cations were formed via the triplet state. The de-protonation of the radical cations takes place to form their fluorenyl radicals.4) The 9-silaphenanthrenes were prepared for the first time by the steady-state photolysis of 9,10-dihydro-9-silaphenanthrene derivatives and their electronic structure was clarified in comparison with that of phenanthrene.5) Thermal hysterisis was observed for the molecular orientation of poly(di-n-dihexylsilane) molecules in their film prepared on the stretched poly(vinyl alcohol) film. The orientation mechanism of poly(di-n-dihexylsilane) molecules were explained on the basis of molecular interaction.6) The conformational change from the helix to random coil of the main chain of the polymethylphenylsilanes with pendant groups of p-nitroazobenzene or p-cyanoazobenzene takes place upon photo-irradiation. This change was induced by the photoisomerization of the pendant azobenzene groups.【Conclusion】Excited-state dynamics of organosilicon compounds were clarified by means of laser flash photolysis and the control of the main chain Information was achieved by photo-irradiation. Less