(I) 對Fe3+具有高螢光選擇性之芳香環1,2,4-噁二唑衍生物之再研究 (II) 合成上緣為冠醚5 與下緣為甲基芘基三唑鎓衍生物之離子對感測 研究

Abstract

第一部分, 我們成功利用1,3-偶極環化加成反應合成1,2,4-噁二唑衍生物24、30a、30b 以及 30c。化合物24 在乙腈中對18 種金屬離子進行螢光篩選，發現其對Fe3+有高度選擇性與強烈的螢光淬熄現象。化合物24 與Fe3+發生不可逆的氧化還原反應，得到主產物X1 與副產物25 和26，這些產物的構造最終都經由有機光譜分析以及X-ray 單晶繞射確認。利用NMR、紫外-可見光光譜與螢光光譜分析後，我們發現含有苯與萘基的 3-芳基-1,2,4-噁二唑衍生物30a-30c 在乙腈中並不會與Fe3+發生氧化還原反應，只有含蒽基的化合物24 為Fe3+之化學劑量器。另外，我們發現蒽在乙腈中可被Fe3+氧化成為oxanthrone，確認它是24 作為Fe3+的化學劑量器的關鍵成分。 第二部份，我們成功的利用即合化學將三唑芘基引入芳杯下緣，再利用碳酸銫將冠醚引入芳杯上緣，形成1,3-交錯構形之56，然後再以Meerwein's reagent將三唑N3位置甲基化得到三唑鎓目標物57。經由紫外-可見光光譜與螢光光譜初步篩選得知，化合物57於17種金屬中只對K+有明顯的淬熄，而在13種陰離子中只有對於I-有些許的淬熄。當57先與K+形成錯化物後，可提升對I-的錯合能力約2倍。利用1H NMR滴定，可以推論化合物57同時錯合K+與I-，也就是離子對之錯合。另外，我們在量測不同濃度的化合物57之NMR光譜時意外發現它有自組裝之現象，經由不同濃度下的57之DOSY光譜得到不同的氫譜擴散係數可證實。

In part 1, we successfully synthesized 1,2,4-oxadiazloe derivatives 24, 30a, 30b and 30c using 1,3-dipolar cycloaddtion reaction of anthryl nitrile oxide with a nitrile group. Compound 24 was found to show a high selectivity toward Fe3+ (among 18 different metal ions) in CH3CN with a strong fluorescence quenching. Compound 24 underwent a Fe3+-induced irreversible oxidation to afford compound X1 as the major product and compounds 25 and 26 as minor products. Compounds X1, 25 and 26 were isolated and characterized by organic spectroscopic data; furthermore, they were also confirmed by single crystal X-ray crystallography analysis.Three other analogues of 3-aryl-1,2,4-oxadiazoles 30a-30c were synthesized, however, they did not undergo Fe3+-induced irreversible oxidation in CH3CN as analyzed by NMR and UV-vis spectroscopy. Among the 3-aryl-1,2,4-oxadiazoles derivatives, we found that only compound 24 with anthracene as a fluorophore is a chemodosimeter for Fe3+. We also found that anthracene alone was oxidized by Fe3+ to afford oxanthrone, which proves that anthracene moiety is the key component of 24 as a Fe3+ selective chemodosimeter.

In part 2, we report the synthesis of 1,3-alternate calix[4]arene derivative 57 using click reaction to get methyl triazoliumpyrene at the lower rim, and crown[5] ether at the upper rim. Compound 57 was found to show a high selectivity toward K+ (among 17 different metal ions) and I- (among 13 different anions) in CHCl3/MeOH (1/3, v/v) with fluorescence quenching. The pre-complex 57．K+ improved its binding ability toward I- by roughly 2 fold as compared to 57 alone. It exhibits a positive heteroditropic sensing effect toward KI. Interestingly, compound 57 was found to exhibit self-assembly behaviour in 1H NMR and DOSY spectra under various concentrations (0.2 to 30 mM in CHCl3).