Electroactive Anion Receptor with High Affinity for Arsenate

Abstract

Herein we present the synthesis and characterization of a macrocyclic polyamide cage that incorporates redox-active 1,4-dithiin units. UV/Vis titration experiments with eight anions in acetonitrile revealed high affinity for H 2 AsO 4 -(logβ 2 = 10.4 +0.4 -0.4 ) and HCO 3 -( ) over other common anionic guests, such as Cl -( ), HSO 4 -( ) and logβ 2 = 8.3 +0.3 -0.4 logK 1:1 = 3.20 +0.03 -0.02 logK 1:1 = 3.57 +0.02 -0.03 H 2 PO 4 -( ), by the selective formation of HG 2 complexes. The recognition of arsenate over phosphate is rare among logK 1:1 = 4.24 +0.05 -0.04both proteins and synthetic receptors, and exploiting the difference in binding stoichiometry represents an underexplored avenue towards developing receptors that can differentiate between the two anions. Additional analysis by 1 H-NMR in 1:3 CD 2 Cl 2 :MeCNd 3 found strong dependence of anion binding stoichiometry with the solvent employed. Finally, titration experiments with cyclic voltammetry provided varying and complex responses for each anion tested, though reaction between the anion and receptors was observed in most cases. These results implicate 1,4-dithiins as interesting recognition moieties in the construction of supramolecular receptors.

Selective separation of light rare-earth elements by supramolecular encapsulation and precipitation

“…Similarly, a pre-organised arene/quinoline-ether tripodal receptor formed a 1:1 host:guest complex with RE(NO 3 ) 3 (MeOH) 3 in methanol through ether-alcohol hydrogen bonding interactions 24 . Pre-organised hexa-substituted arene platforms are well-known to self-assemble into supramolecular tennis-ball structures 25 , 26 , and can encapsulate simple anions such as fluoride, nitrate, and arsenate 27 – 29 .…”

Polarity-Tolerant Chloride Binding in Foldamer Capsules by Programmed Solvent-Exclusion

“…The design of receptors that can capture anions across a range of environments is important for water purification, − clean energy production, − and the extraction of high-value ions. − These needs continue to motivate exploration of new strategies to control anion affinities in water, − across a variety of organic solvents − and in biphasic systems. ,,− ,, It is proving relatively straightforward to design receptors ,− in silico to bind anions effectively in low-polarity organic solvents (ε r < 10) that have weak interaction with dissolved molecules. When those same receptors are deployed in more polar solvents, however, the recognition is more challenging.…”

The Properties, Synthesis, and Materials Applications of 1,4-Dithiins and Thianthrenes

“…114 We found, however, that introduction of the 1,4-dithiin moieties introduces different binding preferences for various anions, demonstrating a high affinity and different binding mode for arsenate (log K 1:1 =5.0-0.3+0.4, log K 1:2 =5.4-0.2+0.2 ) over similarly-sized phosphate (log K 1:1 =4.24-0.04+0.05), as judged by titration experiments in acetonitrile, a rare trait for synthetic anion receptors. 113 We hypothesized this anion binding may stem from the unique properties of 1,4-dithiin over typical arene spacers, namely its non-planarity, preventing interactions with the amide N-H protons, and high polarizability of the sulfur atom, which may better accommodate anionic guests. 113 Though titration experiments with various anions monitored by cyclic voltammetry resulted in altered voltammograms, when oxidized, the receptor demonstrated poor stability in the presence of nearly all guests surveyed.…”

“…113 We hypothesized this anion binding may stem from the unique properties of 1,4-dithiin over typical arene spacers, namely its non-planarity, preventing interactions with the amide N–H protons, and high polarizability of the sulfur atom, which may better accommodate anionic guests. 113 Though titration experiments with various anions monitored by cyclic voltammetry resulted in altered voltammograms, when oxidized, the receptor demonstrated poor stability in the presence of nearly all guests surveyed. 113 In summary, the use of thianthrene and 1,4-dithiin in the construction of supramolecular receptors can produce compounds of unique shape and electronic biases to bind various analytes, but their use as redox-active moieties for the detection of various species has not been well-vetted.…”