含蒽基噁二唑之芳杯衍生物作為對鐵 (III) 離子具高選擇性之螢光化學劑量器

Abstract

本論文成功利用1,3-偶極環化加成方法，在芳杯下緣引入1,2,4-噁二唑蒽基團，成功的合成出針對Fe3+具有高選擇性之螢光化學劑量器45－49。此外，也合成控制化合物50與異咢唑51化合物作為對照組。藉由45與控制化合物50的X-ray單晶繞射可以確認1,2,4-噁二唑蒽基化合物之構造。 由紫外可見光譜與螢光光譜初步篩選實驗可得知，在乙腈溶劑系統下，1,2,4-噁二唑蒽基芳杯化合物45－49、控制化合物50與異咢唑51皆對Fe3+有高度選擇性，具很強的螢光淬熄效果。此外，當加入金屬氧化劑Cu2+，化合物45－47芳杯下緣之羥基亦會被氧化而產生螢光淬熄現象；而化合物48－49、控制化合物50及異咢唑51則僅針對Fe3+有專一性之螢光淬熄現象，且其吸收光譜波形明顯改變。 氫核磁共振滴定光譜實驗數據顯示，化合物46、49與50－51隨著Fe3+的當量逐漸增加，其氫訊號明顯改變，且蒽官能基上的H10訊號消失；藉由Fe2+指示劑我們可以得知含有蒽基噁二唑與異咢唑取代之衍生物與Fe3+在乙腈溶劑下會進行氧化還原反應，而得到Fe2+與其氧化產物。即是當45－51加入Fe3+後，其化學劑量感測模式是藉由Fe3+之氧化力誘使1,2,4-噁二唑蒽基、異咢唑蒽基與芳杯下緣羥基發生氧化反應。 我們藉由合成方式將控制化合物50加入10當量的Fe3+進行氧化還原反應，可單離出氧化產物X1，經由紅外線光譜與碳核磁共振光譜實驗可證實，氧化產物X1其蒽基之C10位置被氧化成羰基，並利用EI-MASS實驗光譜推測可能結構。此外，控制化合物50與Fe3+進行氧化還原反應而得到之副產物63與64也經由X-ray單晶繞射分析鍵定其結構。 將芳杯46加入不同當量的Fe3+進行氧化還原反應，而得到並單離出氧化產物X1與X2－X4，經由紅外線光譜與碳核磁共振光譜實驗可知，氧化產物X3與X4其蒽基之C10位置被氧化成羰基；推測X2為芳杯下緣羥基與Fe3+進行氧化還原反應，所得芳杯上下緣皆被氧化成羰基 (亦即形成對苯醌)，而下緣兩個1,2,4-噁二唑蒽基團仍存在之對稱芳杯結構之產物。

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.