Abstract
In contrast to monotopic receptor 3, the anthracene functionalized squaramide dual-host receptor 1 is capable of selectively extracting sulfate salts, as was evidenced unambiguously by DOSY, mass spectrometry, fluorescent and ion chromatography measurements. The receptors were investigated in terms of anion and ion pair binding using the UV–vis and 1H NMR titrations method in acetonitrile. The reference anion receptor 3, lacking a crown ether unit, was found to lose the enhancement in anion binding induced by the presence of cations. Besides the ability to bind anions in an enhanced manner exhibited by ion pair receptors 2 and 4, changing the 1-aminoanthracene substituent resulted in their exhibiting a lower anion affinity than receptor 1. By using receptor 1 and adjusting the water content in organic phase it was possible to selectively detect sulfates both by “turn-off” and “turn-on” fluorescence, and to do so homogenously and under interfacial conditions. Such properties of receptor 1 have allowed the development of a new type of sensor capable of recognizing and extracting potassium sulfate from the aqueous medium across a phase boundary, resulting in an appropriate fluorescent response in the organic solution.
Highlights
Fluorescent sensors provide a visual method for detecting a wide range of chemical species [1,2]
There is a high degree of interest in novel artificial fluorescent receptors capable of detecting ions due to the fact that anions and cations are ubiquitous in nature and play very important roles in many areas, such as biological research, clinical diagnosis, industries and environmental protection [3,4,5,6]
The concentrations of chloride, bromide, nitrite, nitrate, dihydrogenphosphate and sulfate anions in aqueous phase were determined by high performance ion chromatography (HPIC)
Summary
Fluorescent sensors provide a visual method for detecting a wide range of chemical species [1,2]. The extraction of sodium salts was found to be both less effective and less selective (Supplementary Materials, Figure S64) With these findings in mind, we anticipated that the formation of 4:1 complexes of receptors with sulfates would open the door to detecting this salt selectively. Based on an ion chromatography control, we found that the drop in (Supplementary Materials, Figure S64) To verify this hypothesis, we carried out fluorescence experiments in acetonitrile. Fi=F=Fgiiu2g2g5ru5ue44rre6enn.6m6m.F.)Fl)F.u.lluAouAoro::erraseaefcsfstetceceenrerncncecccoeoernnerrtetsaeapssccppottonowwnnsiseistetehhoofowfwfssaosaotolteulelurutr;ti;toiiBoBon:n:noaaooffftftferererrreecceecexepxptptrtrotaoaorcrcrt1ti1i1oo((nc(ncc=w=w=2i2i2t.t.h3.3h3mmamaqqMMMuue))e)ooiiinununssCCCKKHHH22CCSCSOlOll33344(((u(uu(55nnn00dddmemeerrrMMUUU)V)V;V; CClllii:ig:ggahahhftfttt,t,e,eλλrr λe=exxt2trr5aa4cctntiiomonn).wwAiitt:hhaafatqqeurueecoouunstsaKKcCtCwll((i55t0h0mwmMaMte)).r. ; B: after extraction with aqueous K2SO4 (50 mM); C: after extraction with aqueous KCl (50 mM)
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