Photoreactions of pi-Electron-System-Substituted Disilanes and their Application to Photoactive Polymers

合成了由二硅基团和pi电子体系组成的交替聚合物聚[二硅烯]、聚[二硅烯-1，4-二烯]和聚[二硅烯]乙炔，并研究了它们的光化学性质。在空气中紫外光照射后，薄膜中的Si-Si键发生断裂，形成Si-O键。还研究了聚合物在溶液中的光解反应。因此，当这些聚合物在苯中存在或不存在捕捉剂的情况下被光解时，可以通过假设硅基自由基由硅-硅键的均质裂解形成的产物得到最好的解释。由此形成的硅基在所使用的条件下经历两个不同的反应。一个涉及歧化反应，导致硅烯和氢硅烷的形成，而另一个涉及跨pi-电子体系的交联加成反应。在这些光反应中，发现在聚合物主链的硅原子上引入烷基有利于交联反应，而芳基取代烷基有利于歧化反应。为了更好地了解这些聚合物的光化学性质，我们制备了二硅苯齐聚物作为模型化合物，并研究了它们的光化学行为。

Alternating polymers composed of a disilanylene group and pi-electron system, poly[(disilanylene)phenylenes], poly[(disilanylene)naphthylenes], poly[(disilanylene)thienylenes], poly[(disilanylene)dithienylenes], poly[(disilanylene)butenyne-1, 4-diyls], and poly[(disilanylene)ethynylenes] were synthesized and their photochemical properties were investigated.These polymers are soluble in common organic solvents and can be casted to thin solid films by spin-coating. UV-irradiation of the films in air caused the cleavage of the Si-Si bonds leading to the formation of Si-O bonds. Photolysis of the polymers in solution was also investigated. Thus, when these polymers were photolyzed in the presence or absence of a trapping agent in benzene, products which can be best explained by assuming the silyl radicals formed by the homolytic scission of an Si-Si bond were obtained. The silyl radicals thus formed undergo two different reactions under the conditions used. One involves the disproportionation reaction leading to the formation of a silene and hydrosilane, while the other comprises a cross-linking addition reaction across the pi-electron system. In these photoreactions, it was found that introduction of an alkyl group on the silicon atom in the polymer, main chain is favorable for the cross-linking reaction, while replacement of the alkyl group by an aryl group facilitates the disproportionation reaction. It was also found that the extension of the pi-electron system in the polymer chain results in the decrease of the photoactivities of the present polymers.In order to learn more about the photochemical properties of these polymers, we prepared disilanylene-phenylene oligomers as model compounds and investigated their photochemical behavior.