高感度金屬陽離子感測器之設計與合成及其應用

本研究主要目的在設計及合成高感度的陽離子螢光感測器。以激發態分子內質子轉移(excited-state intramolecular proton transfer)的發光機制為訊號讀出單元再結合冠醚分子(63)為金屬離子的辯識單元，藉由改良式的曼尼希反應，在發光團上引入冠醚分子。利用這樣的分子探討鈉離子和鈣離子及其他不同的陽離子對整個分子的發光現象有什麼不同。由實驗結果得知，鈉離子會鍵結在冠醚上而使得螢光感測分子67 的無法進行激發態質子轉移的發光機制，導致其螢光強度減低，而且放光波長產生藍位移的現象。而跟鈣離子作用時，由於鈣離子的鹼性較高會使的感測器上的羥基上的質子脫附，造成整個分子的共振變長產生更強的螢光，放光波長也產生紅位移。另外也利用不同的發光團合成出不同的衍生物，化合物62具有兩個可以產生分子內氫鍵(intramolecular hydrogen bonding)的位置[O–H----NR2 (conformer A) and O–H----O=C (conformer B)]，研究構型A和構型B發光時的差別和重要性及其競爭性激發態分子內質子轉移的現象。應用這樣的發光機制和冠醚分子做結合，化合物64和65能夠成功的辨識鈉離子和鈣離子且都有很高的結合常數。因此我們的研究結果顯示利用激發態分子內質子轉移成功的發展出一個新型的陽離子感測器。

關鍵字

激發態分子內質子轉移；螢光感測器；金屬陽離子

並列摘要

A new metal ion probe 8-(1,4,7,10-tetraoxa-13-azacyclopentadec- 13-ylmethyl)quinolin-7-ol (67) was synthesized via a modified Mannich reaction, in which the mechanism of recognition incorporates excited-state proton transfer reactions. The remarkable differentiation in spectral properties upon metal complexation makes 67 a highly sensitive fluorescence probe. 1-[(Diethylamino)-methyl]-2-hydroxy-3-naphthaldehyde 62 (DMHN) possessing dual hydrogen bonding (HB) sites (O–H----NR2 (conformer A) and O–H----O=C (conformer B)) has been synthesized to study the competitive excited-state intramolecular proton transfer (ESIPT) reaction. Despite near degeneracy between conformers A and B, the associated chromophores are significantly different and can be rationalized by different degrees of hydrogen bond-induced  electrons delocalization. ESIPT takes place in both conformers A and B in cyclohexane, resulting in a zwitterion (max ~485 nm) and an extremely weak keto-tautomer max ~730 nm) emission, respectively. The response-limited rise dynamics for both A and B conformers (<150 fs) leads us to conclude that both ESIPT processes are essentially barrierless and the interconversion between two HB conformers is prohibited in the excited state. We reported the design and synthesis of a new type of metal-cation probes, 3-hydroxy-4-(1,4,7,10-tetraoxa-13-azacyclopentadec-13-ylmeth -yl)naphthalene-2-carbaldehyde (64) and its single hydrogen-bond analogue 1-(1,4,7,10-tetraoxa-13-azacylopentadec-13-ylmethyl)-2- naphthol (65), in which 1-aza-15-crown-5 ether (63) in combination with the naphthol oxygen acts as a receptor, while the mechanism of excited-state intramolecular proton transfer (ESIPT) is exploited as a signal transducer. The association constant of 25000 M-1, 38000 M-1, (5500 M-1 and (12000 M-1 for the formation of 64/Na+, 64/Ca2+, 65/Na+ and 65/Ca2+ complexes, respectively, in CH3CN plus drastic fluorescence changes due to the fine-tuning of ESIPT reaction upon complexation, lead 64 and 65 to be highly sensitive fluorescent sensors. The results add a new class into the category of metal-cation probes, with the perspective of designing ESIPT systems capable of sensing bio-analytes.

並列關鍵字

metal cation probe ； ESIPT ； hydrogen bonding ； crown

參考文獻

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高感度金屬陽離子感測器之設計與合成及其應用

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