| Summary: | 碩士 === 臺灣大學 === 化學研究所 === 95 === This thesis is mainly a study on aminostilbene-based fluoroionophores with character of twisted intramolecular charge transfer（TICT）. Our previous research has shown that trans-(N-(4-methoxylphenyl)amino)stilbene（1OM）forms a TICT state upon electronic excitation by twisting the C-N bond and thus possesses low fluorescence quantum yields. We have taken the advantage of this TICT behavior for the design of new fluoroionophores and synthesized a series of trans-4-(N-arylamino)stilbenes containing a hydrazone substituent, namely 1Hz、2Hz and 3Hz. According to literatures, the hydrazone and methoxyl groups can selectively interact with Cu2+ ion. We except that the electron donating ability of the methoxy group will decrease upon binding with Cu2+, which would inhibit the formation of TICT and result in an enhancement of fluorescence intensity and an off-on fluoroionophoric behavior. The results indeed show that the fluorescence of 1Hz、2Hz and 3Hz only respond to the present of Cu2+ in acetonitrile solution, and the magnitude of fluorescence response is 2Hz > 1Hz > 3Hz. However, similar fluoroionophoric behavior is also observed for compounds without the hydrazone group, revealing that the amino nitrogen atom rather than the hydrazone group is responsible for interactions with Cu2+. Thus, the interpretation of fluoroionophoric behavior in the literature needs to be reexamined.
We have also investigated the effect of π-conjugated length on the TICT behavior of aminostilbenes by adding a phenyl group to different positions of 1OM（i.e. 3OM and 4OM）. The results show that both 3OM and 4OM posses higher fluorescence quantum yield than 1OM, indicating that the TICT character is largely suppressed. In particular, compound 3OM has a fluorescence quantum yield as large as 0.95 in dichloromethane, which indicate that the TICT formation is unimportant for 3OM in dichloromethane.
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