摘要
合成了 1 ,n-双 [4 -[2 -[2 -( 5-甲基苯并唑基 ) ]乙烯基 ]苯氧基 ]烷烃 ( a:n=3 ; b:n=4 ; c:n=6)和 2 ,2 -双 [4 -[2 -[2 -( 5-甲基苯并唑基 ) ]乙烯基 ]苯氧基 ]乙醚 ( d) 4个新化合物 .用元素分析、红外、紫外、核磁共振谱和质谱表征了其结构 .用紫外吸收光谱跟踪研究了 a_ d在紫外灯照射下的变化 ,发现上述化合物在高压汞灯照射下可同时发生反顺异构化和 [2 +2 ]分子内光二聚两种反应 ,反顺异构化反应迅速可逆 ,而光二聚反应进行缓慢且不可逆 .增加链长有助于提高分子内光二聚反应的速率 .分子内光二聚反应不受空气中氧的影响的事实表明其是经激发单线态历程进行的 .还发现分子内光二聚体在短波紫外光照射下容易进行逆 [2 +2 ]光解开环反应 .上述化合物分子内光二聚和光解开环反应可以反复进行多次 。
n Bis[trans 4 [2 [2 (5 methylbenzoxazolyl)]ethenyl]phenoxy]alkanes[n=3(Ⅰa), 4(Ⅰb), 6(Ⅰc)] and 2,2 bis[trans 4 [2 [2 (5 methylbenzoxazolyl)]ethenyl]phenoxy]ethyl ether(Ⅰd) were synthesized. Their structures were identified by elemental analysis, IR, UV, 1H NMR, 13 C NMR and MS. The UV spectra were used to illustrate the change of compounds Ⅰa_Ⅰd under the irradiation of high pressure mercury lamp. It was found that these compounds undergo two kinds of reactions, the trans cis isomerization and intramolecular photodimerization. The former is fast and reversible, and the latter is slow and irreversible. The speed of intramolecular photodimerization will increase with increasing the length of the carbon chain between the two 2 [2 (5 methylbenzoxazolyl)]ethenyl]phenyl group. The fact that the photodimerization is not affected by oxygen shows that the reaction proceeds through an excited singlet state. It is also revealed that compounds Ⅰa_Ⅰd undergo [2+2] photolysis easily when irradiated under short UV light. That the intramolecular photodimerization and photolysis of these compounds can repeat many times indicate that these compounds have a high photostability.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2000年第8期1211-1215,共5页
Chemical Journal of Chinese Universities
基金
国家自然科学基金! (批准号 :2 960 2 0 0 6)
关键词
双杂芳基乙烯
分子内光二聚
合成
光解
光化学
Bisheteroarylethene
Intramolecular photodimerization
trans cis Isomerization
Photolysis
