Abstract

A series of fluorescent and non-fluorescent multipodands, substituted with donor S, N, and O heteroatoms, bridged to mesitylene and benzene core at 1, 3-, 1, 3, 5-, and 1, 2, 4, 5-positions have been synthesized and characterized. The liquid–liquid extraction experiment showed that non-fluorescent podands such as mono-, di-, tri-, and tetrapod exhibited excellent complexation abilities towards Ag⁺ ions. The tetrapodand (O, N) shows highest extraction of Ag⁺ (73%) and tetrapodand (S, N) shows the highest Ag⁺/Pb²⁺ selectivity (135). However, for fluorescent dipodands very weak complexation ability towards metal ions were observed likely due to steric crowding. Significantly, these fluorescent dipodands undergoes protonation at very low pH (ca. < 1.0), reminiscent of acid stability—a structural feature of blue copper proteins. The NMR analysis of fluorescent podands showed that amine-appended anthracene moiety(ies) almost fills the podand cavity as lid, shifting most of the protons upfield (~ 0.5 ppm), thus causing acid stability.

Graphic abstract

中文翻译：

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荧光但被“窒息”的多足分子：Ag（I）络合和NMR研究

摘要

一系列被施主S，N和O杂原子取代的荧光和非荧光多足体，在1，-3、1、3、5、5和1、2、4、5位上桥接至均三甲苯和苯核已经合成和表征。液-液萃取实验表明，单-，二-，三-和四足等非荧光荚膜对Ag ⁺离子具有优异的络合能力。四足体（O，N）显示出最高的Ag ⁺提取率（73％），四足体（S，N）显示出最高的Ag ⁺ / Pb ²⁺选择性（135）。但是，对于荧光二足体，由于空间拥挤，观察到对金属离子的络合能力很弱。值得注意的是，这些荧光二足体在非常低的pH值（约<1.0）下会发生质子化，让人联想到酸稳定性（蓝色铜蛋白的一种结构特征）。荧光Podands的NMR分析表明，胺附加的蒽部分几乎充满了Podand腔的盖子，使大部分质子向高场移动（〜0.5 ppm），从而引起酸稳定性。

图形摘要