N‐Alkyl Ammonium Resorcinarene Salts as High‐Affinity Tetravalent Chloride Receptors

Abstract

N-Alkyl ammonium resorcinarene salts (NARYs, Y=triflate, picrate, nitrate, trifluoroacetates and NARBr) as tetravalent receptors, are shown to have a strong affinity for chlorides. The high affinity for chlorides was confirmed from a multitude of exchange experiments in solution (NMR and UV/Vis), gas phase (mass spectrometry), and solid-state (X-ray crystallography). A new tetra-iodide resorcinarene salt (NARI) was isolated and fully characterized from exchange experiments in the solid-state. Competition experiments with a known monovalent bis-urea receptor (5) with strong affinity for chloride, reveals these receptors to have a much higher affinity for the first two chlorides, a similar affinity as 5 for the third chloride, and lower affinity for the fourth chloride. The receptors affinity toward chloride follows the trend K1 ≫K2 ≫K3 ≈5>K4, with Ka =5011 m(-1) for 5 in 9:1 CDCl3/[D6]DMSO.

High-affinity and selective detection of pyrophosphate in water by a resorcinarene salt receptor

“…In a recent study in organic media, 33 the NARX receptors were shown to be highly selective for the chloride anion over other anions such as bromide, iodide, nitrate, triflate and picrate. The specificity towards chloride was determined to be due to both its suitable size, it fits perfectly between two adjacent ammonium moieties, as well as its strong H-bond acceptor behaviour.…”

“…The NARXs are held together by several weak interactions, emphasized by the many species usually seen in their traditional mass spectra. 31 – 33 …”

“… 27 – 32 This is especially true when the counter anions are either chlorides or bromides. 33 Moreover, different upper rim functional groups can significantly influence the binding abilities of the cavitand as a whole. 31 , 32 The NARXs have been used as supramolecular receptors for neutral 31 , 32 and anionic 33 , 34 guests in organic media and as synthons for larger supramolecular architectures held together by halogen bonds.…”

“… 33 Moreover, different upper rim functional groups can significantly influence the binding abilities of the cavitand as a whole. 31 , 32 The NARXs have been used as supramolecular receptors for neutral 31 , 32 and anionic 33 , 34 guests in organic media and as synthons for larger supramolecular architectures held together by halogen bonds. 35 The insolubility of the NARXs in water has limited their application to biological processes.…”

Bamboo-like Chained Cavities and Other Halogen-Bonded Complexes from Tetrahaloethynyl Cavitands with Simple Ditopic Halogen Bond Acceptors

“…Resorcinarenes, [29][30][31][32][33][34][35][36][37] their salts, [38][39][40][41][42][43][44] and resorcinarene cavitands [22][23][24][25][26]28,[45][46][47][48][49] are well-studied families of macrocyclic receptors. Resorcinarenes are particularly useful due to their ease of preparation, simplicity of functionalization, and versatility as hosts for a wide variety of guests.…”