偶氮冠醚橋聯雙芳杯之合成及其對胺與金屬離子之顏色感測

Abstract

修飾上偶氮基團的冠醚芳杯，當它與客體錯合時，會引起電荷密度改變，因而誘發偶氮基團變色，所以可用肉眼觀測辨識結果。 本論文中合成了對位-對位與對位-鄰位之冠醚橋聯雙芳杯43a,b與44a,b。並且找出合成具有位向選擇性的反應條件：在叔丁醇鉀與二甲基甲醯胺中，可得到化合物43a,b，產率是35□50%；在氫化鈉與二甲基甲醯胺中，則可得到44a,b，產率是20□25%。緊接著我們在43a,b上修飾單或雙偶氮基團得到51a,b與52a,b，然後針對胺與金屬陽離子進行辨識。在氯仿中51a,b與52a,b對胺均無辨識效果。然而52a與52b在乙腈與氯仿 (v/v = 99:1) 中對Ca2+與Pb2+離子具有選擇性，在紫外-可見光光譜上分別由394 nm紅位移到520與510 nm。利用紫外-可見光光譜滴定實驗計算出化合物52a與Pb2+的logKa為5.06，52a對Ca2+為3.41、52b對Pb2+及Ca2+的錯合常數各為4.03和3.78。 透過52b對Pb2+在CD3CN與CDCl3 (v/v = 97:3) 中的1H NMR滴定實驗中訊號不對稱的分裂與位移，我們判斷應是由於Pb2+在彎曲的冠醚雙芳杯的凹面與冠醚孔洞錯合後導致雙芳杯形成不對稱之結構。同時導致偶氮苯下緣的羥基電子密度改變而導致光譜紅位移。

Diazo-chromophores bearing calixcrowns were reported to give color change upon specific metal ion complexation. Here we synthesized a series of biscalix[4]crown 43a,b and 44a,b, and further functionalized with diazo chromophores to give 51a,b and 52a,b in 40 ~ 50%, respectively. The complexation ability of compounds 51a,b and 52a,b toward ammonium ions and metal cations were studied. The results showed that 51a,b and 52a,b have low complexation ability toward ammonium ions in CHCl3, since the recognition site of crown cavity is blocked by the propyl groups. Compounds 52a,b showed high selectivity toward Pb2+and Ca2+ cations in CH3CN/CHCl3 (v/v = 99:1) with bathochromic shift of their absorbtion spectra. The association constant (logKa) of 52a⋅Pb2+、52a⋅Ca2+、52b⋅Pb2+ and 52b⋅Ca2+ are 5.06、3.41、4.03 and 3.78。 Through the asymmetric shift and splitting of 1H NMR titration spectra of 52b with Pb2+ cation, we propose the Pb2+ cation form an unsymmetric complex with the banded 52b at the concave side of the crown cavity.