Abstract: 1,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, ¹³C NMRand MS. The UVspectra 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 UVlight. That the intramolecular photodimerization and photolysis of these compounds can repeat many times indicate that these compounds have a high photostability.

Key words: Bisheteroarylethene, Intramolecular photodimerization, trans-cis Isomerization, Photolysis