作者:Larry A. Cabell、Michael D. Best、John J. Lavigne、Stephen E. Schneider、Denise M. Perreault、Mary-Katherine Monahan、Eric V. Anslyn
DOI:10.1039/b008694k
日期:——
A metal containing fluorescent chemosensor was designed, synthesized, and studied for the quantification of citrate in common beverages. The sensor consists of Cu(II) bound by a 1,10-phenanthroline ligand which is attached to a bis(aminoimidazolium) receptor (5). Receptor 5 was designed such that binding of the metal creates an additional binding site for citrate. This additional binding interaction was found to increase the metal and citrate binding constants in a cooperative manner, yielding a minimum 2.0 fold increase in the citrate binding constant and a minimum 2.0 fold increase in the Cu(II) binding constant. Further, 5 was designed so that binding of Cu(II) quenches a photo-excited state of the 1,10-phenanthroline fluorophore. Thus, addition of citrate to 5–Cu(II) resulted in an increase of the fluorescence of the system. The nature of the fluorescence modulation upon citrate binding was probed using a model compound (6–Cu(II)). The data support an increase of electron density on the metal due to the donating ability of a carboxylate anion of citrate. In a sensing assay, the receptor is effective for measuring citrate concentrations in the micromolar range in highly competitive media. We believe this is the first demonstration of anion sensing in which the fluorescence emission is modulated due to a perturbation in the metal quenching effect upon analyte binding.
设计、合成并研究了一种含荧光化学传感器的金属络合物,用于检测常见饮料中的柠檬酸盐含量。该传感器由与1,10-菲罗啉配体结合的Cu(II)构成,该配体连接到一个双(氨基咪唑鎓)受体(5)上。受体5的设计使得金属结合后形成额外的柠檬酸盐结合位点。研究发现,这种额外的结合相互作用以协同方式增加了金属和柠檬酸盐的结合常数,使柠檬酸盐结合常数至少增加2.0倍,Cu(II)结合常数至少增加2.0倍。此外,设计5使得Cu(II)结合会淬灭1,10-菲罗啉荧光团的激发态。因此,向5-Cu(II)中添加柠檬酸盐会提高系统的荧光强度。通过使用模型化合物(6-Cu(II))探测了柠檬酸盐结合后荧光调制的特性。数据支持由于柠檬酸盐羧酸根离子的供电子能力,金属上的电子密度增加。在传感测定中,该受体有效地测量了在高度竞争性介质中微摩尔级的柠檬酸盐浓度。我们相信这是首次证明阴离子传感,其中由于分析物结合时金属淬灭效应的扰动,荧光发射发生了调制。