| Summary: | 碩士 === 國立交通大學 === 應用化學系碩博士班 === 99 === We report here the design and synthesis of a series of highly selective fluorescent chemodosimeters 45－49 for Fe3+, where 1,2,4-oxadiazoles were introduced to the lower-rim of calix[4]arene by using 1,3-dipolar cycloaddtion of aryl nitrile oxides with nitrile groups. Control compound 50 and isoxazole 51 were also synthesized for comparison. Structures of anthryl-1,2,4-oxadiazolyl cailx[4]arenes 45 and 50 were confirmed by X-ray diffraction analysis.
Anthryl-1,2,4-oxadiazole substituted calix[4]arenes 45－49 all showed a high selectivity and strong fluorescence quenching toward Fe3+ among 17 other metal perchlorate salts in CH3CN. Moreover, in the presence of Cu2+, the metal based oxidant, phenolic-OH of calix[4]arenes 45－47 were oxidized and their fluorescence was turned off.
Results from the 1H NMR titration of 46, 50 and 51 showed that all proton signals were significantly shifted and the anthryl-H10 signal disappeared. Because Fe2+ could be easily detected by ferrozine, the irreversible chemical reaction between anthryl-1,2,4-oxadiazole group and Fe3+ was confirmed to be a redox reaction.
The oxidation of the control compounds 50 led to the formation of products X1, where the anthryl-C10 was found to be oxidized into a carbonyl group. Based on X1 molecular ion from Mass we propose the possible structures of the unknown X1. Two other by-products 63 and 64, resulting from the oxidation of the control compound 50, were confirmed by single crystal X-ray analysis.
Upon addition of different amounts of Fe3+, the oxidation of lower- rim bis-anthryl-1,2,4-oxadiazoly calix[4]arene 46 led to the formation of products X2－X4. From 1H, 13C NMR, and IR spectra of X3－X4, we found that the anthryl-C10 was oxidized into carbonyl group (C=O). Moreover, the lower rim phenol of calix[4]arene was oxidized into carbonyl group (C=O) which formed the oxidation product X2.
|
|---|
