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

有机硅化合物和有机硅聚合物由于其光致发光、电致发光和光电导性能而引起人们的广泛关注。在本研究中，1）为了阐明有机硅化合物的激发态性质，我们利用纳秒激光闪光光解和荧光测量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与功能之间的关系，我们研究了聚硅烷分子在其薄膜中的取向，以及通过光照射控制主链构象。获得了以下结果。[结果]1）测定了9，10-二氢-9-硅菲蒽和9-硅芴衍生物等10余种有机硅化合物的光物理参数; 2）在芳香族化合物中引入硅基取代基后，由于取代基与荧光量子产率之间的相互作用，荧光量子产率显著提高; 3）在有机硅化合物中引入硅基取代基后，荧光量子产率显著降低，荧光量子产率显著降低; 4）在有机硅化合物中引入硅基取代基后，荧光量子产率显著提高，荧光量子产率显著降低; 5）在有机硅化合物中引入硅基取代基取代基后，荧光量子产率显著降低。 关于我们 Si-C键的σ-电子和芳环的π-电子。而在硅取代的化合物如9，10-二氢-9-硅杂菲和9-硅芴衍生物中，观察到荧光量子产率的降低。这一现象可以用硅取代化合物中的系间交叉增强来解释。3）9-硅芴衍生物通过两步双色纳秒光解，通过三重态形成自由基阳离子。自由基阳离子发生去质子化形成芴基自由基。4）首次通过9-硅菲的稳态光解制备了9-硅菲，10-二氢-9-硅杂菲衍生物的结构与菲的结构进行了比较，并阐明了它们的电子结构（二-正-二己基硅烷）分子在它们的膜中在拉伸的聚（乙烯醇）膜上制备。从分子间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基偶氮苯侧基的聚甲基苯基硅烷在光照射下发生主链由螺旋构象向无规卷曲构象的转变。这种变化是由侧链偶氮苯基团的光异构化引起的。【结论】利用激光闪光光解技术研究了有机硅化合物的激发态动力学，实现了对主链信息的调控。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