An Anion‐Modulated Three‐Way Supramolecular Switch that Selectively Binds Dihydrogen Phosphate, H₂PO₄⁻

Abstract

An anionic three-way switch A bipyridyl bisurea-based anion receptor that is highly selective for dihydrogen phosphate demonstrates spectroscopically distinct anion bound conformations toward halides and select oxoanions. 1H NMR studies show the differing anion induced conformations are reversible allowing this system to function as a three-way molecular switch.

Solid-State Examination of Conformationally Diverse Sulfonamide Receptors Based on Bis(2-anilinoethynyl)pyridine, -Bipyridine, and -Thiophene

“…Known bis-aniline 16 was similarly prepared from 6,6′-dibromo-2,2′-bipyridine. 34 Independent treatment of 15 and 16 with p -toluenesulfonyl chloride in pyridine provided expanded receptors 11 and 12 in moderate to very good yield.…”

“Off-on” aggregation-based fluorescent sensor for the detection of chloride in water

“…Chloride must sit inside the cleft formed from an S or W arrangement in order to H-bond to the R 3 N + H and HC Py protons, similar to what is observed when our related bipyridine-based receptor binds chloride or bromide (referred to as the Z arrangement). 30 As discussed, additional equilibria arise during the titration of bromide or chloride into 1 + , likely indicating a competing 1: 2 interaction. What is unclear is whether this secondary equilibrium occurs with the pyridinium NH proton ( 1:2 S ) or CH proton ( 1:2 W ).…”

Ion and Molecular Recognition Using Aryl–Ethynyl Scaffolding

“…Within our group we have found that an aryl–ethynyl scaffold can adopt varying conformations in the solid state or in solution when influenced by a guest (see below). [27–29] These conformational changes have a direct effect on the conjugation throughout the system, giving rise to differences in the emission spectra.…”

“…We have previously described a series of both bis(-sulfonamido)- and bis(urea)ethynylpyridines that exhibit positive fluorescent responses to anions with the right combination of electron-donating and/or electron-withdrawing substituents on the pendant phenyl rings. [4, 25–29, 77] The bis-ureas (e.g., 25 – 28 , Figure 17) exhibit a rich solvent-based conformational dependence, showing in the solid state that “S”-, “U”- and “W”-type conformations are all possible depending on solvent guests (for instance, “S” shown in 28 , “U” shown in 25 – 27 ). [27] …”

“…Bipy-based ligand 28 (Figure 17) was designed as a selective probe for the complexation of H 2 PO 4 − over halides and other oxoanions. [29, 80] Including hydrogen bond acceptors and donors in the binding pocket improved the selectivity by matching the two-donor, two-acceptor architecture of H 2 PO 4 − and allowed the host to bind this ideal guest in a “U” conformation. Titrations and X-ray crystal structures revealed an alternative “S” binding mode for the halides, wherein a urea arm rotates about the alkyne linkage to form a C–H···X − hydrogen bond at the 3-position of the bipy subunit.…”