Fluorescent anion sensing by bisquinolinium pyridine-2,6-dicarboxamide receptors in water
作者:Alejandro Dorazco-González、Marcos Flores Alamo、Carolina Godoy-Alcántar、Herbert Höpfl、Anatoly K. Yatsimirsky
DOI:10.1039/c3ra44363a
日期:——
Dicationic N-methylated at quinolyl moieties derivatives of three isomers of N,N′-bis(quinolyl)pyridine-2,6-dicarboxamide, and respective N-methyl quinolinium benzamides as reference compounds, have been prepared and characterized by crystal structures, spectral and acid–base properties in water. First pKa values of dicarboxamides between 8.1 and 9.3 determined spectrophotometrically are unusually low for amides. Dicarboxamide derivatives of 3- (1) and 6-aminoquinoline (2) undergo efficient fluorescence quenching by halide, acetate, pyrophosphate and nucleotide anions but the derivative of 5-aminoquinoline (3) shows very small quenching effects. The shape of Stern–Volmer plots for dicarboxamides indicates the existence of ground state complexation with anions, which is absent for related benzamides. Association constants, KA, with anions were calculated from analysis of concentration profiles of the quenching effects on the fluorescence of 1 and 2. Quenching by nucleoside triphosphates is much more efficient than by inorganic anions. Efficient binding of even simple inorganic anions by neutral amide N–H donors in water is attributed to high acidity of amides and preorganized rigid structure of the receptors.
我们制备了 N,N′-双(喹啉基)吡啶-2,6-二甲酰胺的三种异构体的 N-甲基喹啉基二icationic 衍生物,并以各自的 N-甲基喹啉鎓苯甲酰胺作为参照化合物,通过晶体结构、光谱和水中的酸碱特性对其进行了表征。用分光光度法测定的二羧酰胺的第一个 pKa 值介于 8.1 和 9.3 之间,对于酰胺类化合物来说是异常低的。3- (1) 和 6- 氨基喹啉 (2) 的二羧酰胺衍生物会受到卤化物、醋酸盐、焦磷酸盐和核苷酸阴离子的有效荧光淬灭,但 5- 氨基喹啉 (3) 衍生物的淬灭效果很小。二羧酰胺的 Stern-Volmer 图的形状表明存在与阴离子的基态络合,而相关的苯甲酰胺则不存在这种络合。通过分析 1 和 2 荧光淬灭效应的浓度曲线,计算出了与阴离子的关联常数 KA。核苷三磷酸酯的淬灭作用比无机阴离子的淬灭作用有效得多。即使是简单的无机阴离子也能与水中的中性酰胺 N-H 给体有效结合,这归因于酰胺的高酸度和受体的预组织刚性结构。