Design, Synthesis and Application of Highly Sensitive Metal Cation Sensors
Date Issued
2005
Date
2005
Author(s)
Wu, Kun-Chan
DOI
zh-TW
Abstract
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.
Subjects
激發態分子內質子轉移
螢光感測器
金屬陽離子
metal cation probe
ESIPT
hydrogen bonding
crown
Type
thesis
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