雜環取代之新型香豆素衍生物的合成與金屬離子感應性質研究

Abstract

本論文的設計構想是選用7-甲氧基香豆素為螢光基團，以1,4-三唑與二甲基-2-吡啶(DPA)這兩種雜環取代基為金屬離子的辨識元件，再分別透過亞甲基、乙醯基和醯胺基進行連結，即可組合成一系列以香豆素為主體結構的新型螢光金屬離子感應分子13、14、15及17。 利用光譜儀來測量這些化合物在乙腈溶液中的光物理性質及離子感應能力後發現，四種化合物的螢光訊號變化和離子選擇性皆不相同。其中，15和17對特定金屬離子有明顯的偵測能力，混合後螢光強度會大幅增強，但13及14與金屬離子混合後，螢光訊號的改變幅度不如15及17的顯著，因此我們只對15和17進行詳細的1H-NMR、UV-vis及螢光光譜的滴定。 實驗結果顯示，具亞甲基架橋的15傾向與鈣、鎂、鋅、鎘離子形成1:1的錯合物，而具有醯胺架橋的17則可能與多當量數的鋅、鎘離子進行螯合。利用Hill plot分析17與這兩種離子的錯合比例可能是1:2，然而Job plot卻推測17與兩種離子生成2:3的錯合物。由於兩種實驗結果並不一致，我們還需要找尋其他的分析方法來得知實際的錯合比例和錯合模式。

Based on our design, 7-methoxycoumarin was chosen as the fluorophore, and heterocyclic building blocks, such as 1,4-triazole and di-2-picolylamino (DPA) groups, were ultilized as the ionophores for metal ions. These two units were jointed with methylene, acetyl, and amide bridges respectively to afford a series of novel coumarin-based fluoroionophores 13, 14, 15, and 17. The photophysical and metal ion-sensing properties of these products were examined in acetonitrile. The changes in fluorescence and ion selectivity of each product were found to be different from one another. 15 and 17 were capable of detecting specific metal ions by showing dramatic enhancement of fluorescence. In contrast with 15 and 17, the fluorescence signals of 13 and 14 were inefficiently altered by metal ions. Hence, 15 and 17 were further investigated with detailed 1H-NMR, UV-vis, and fluorescence titrations. In our research, methylene-bridged 15 is prone to form 1:1 complexes with Ca2+, Cd2+, Mg2+, and Zn2+, and amide-bridged 17 is probably chelated with multiple equivalences of Cd2+ and Zn2+. The complexation stoichiometries of 17 with Cd2+ and Zn2+ were calculated to be 1:2 with Hill plots, but Job plots indicated 2:3 complexes were formed between 17 and those metal ions. Because of the inconsistent results, other analytical methods will be required to obtain the actual binding ratios and complexation models.