Extraction and transport of sulfate using macrocyclic squaramide receptors

Qin, Lei; Vervuurt, Sacha J. N.; Elmes, Robert B. P.; Berry, Stuart N.; Proschogo, Nicholas; Jolliffe, Katrina A.

doi:10.1039/c9sc04786g

Cited by 52 publications

(60 citation statements)

References 51 publications

(70 reference statements)

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“…10h However, because it uses an anion receptor as a transporter, this process and all those reported so far in the literature required the assistance of lipophilic counterion. 10 We envisioned that by using receptor 2 it would be possible to eliminate this drawback, and for the first time, transport sulfates in the form of alkali metal salts across a membrane. For comparative purposes, we investigated the U-tube transport experiments with both scenarios where the aqueous source phase contained a 50 mM solution of TBA 2 SO 4 or K 2 SO 4 and the bulk chloroform phase contained 5 mM receptor 2 .…”

Section: Resultsmentioning

confidence: 99%

“…The group of these compounds mainly includes anion receptors: macrocyclic calix[ n ]pyrroles, TREN-based hexaurea, diiminoguanidine, and more recently macrocyclic squaramide derivatives. 10 Some of these receptors were found to recognize sulfate salts in unusual manner via contact ion pair interactions. 11 However, this approach requires the assistance of lipophilic counterions during the extraction or transport processes.…”

Section: Introductionmentioning

confidence: 99%

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Cooperative Transport and Selective Extraction of Sulfates by a Squaramide-Based Ion Pair Receptor: A Case of Adaptable Selectivity

et al. 2020

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The use of a squaramide-based ion pair receptor offers a solution to the very challenging problem of extraction and transport of extremely hydrated sulfate salt. Herein we demonstrate for the first time that a neutral receptor is able not only to selectively extract but also to transport sulfates in the form of an alkali metal salt across membranes and to do so in a cooperative manner while overcoming the Hofmeister bias. This was made possible by an enhancement in anion binding promoted by cation assistance and by diversifying the stoichiometry of receptor complexes with sulfates and other ions. The existence of a peculiar 4:1 complex of receptor 2 with sulfates in solution was confirmed by UV–vis and 1 H NMR titration experiments, DOSY and DLS measurements, and supported by solid-state X-ray measurements. By varying the separation technique and experimental conditions, it was possible to switch the depletion of the aqueous layer into extremely hydrophilic or less lipophilic salts, thus obtaining the desired selectivity.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cooperative Transport and Selective Extraction of Sulfates by a Squaramide-Based Ion Pair Receptor: A Case of Adaptable Selectivity

et al. 2020

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“…Three trends can be distinguished in research on the synthesis of such systems. A first approach uses macrocyclic anion receptors with a properly designed binding cavity for a tetrahedral sulfate anion [ 12 , 13 , 14 ]. The second approach involves designing acyclic receptors capable of forming stable complexes with sulfate anions through self-organization [ 15 , 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

2021

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Combining three features—the high affinity of squaramides toward anions, cooperation in ion pair binding and preorganization of the binding domains in the tripodal platform—led to the effective receptor 2. The lack of at least one of these key elements in the structures of reference receptors 3 and 4 caused a lower affinity towards ion pairs. Receptor 2 was found to form an intramolecular network in wet chloroform, which changed into inorganic–organic associates after contact with ions and allowed salts to be extracted from an aqueous to an organic phase. The disparity in the binding mode of 2 with sulfates and with other monovalent anions led to the selective extraction of extremely hydrated sulfate anions in the presence of more lipophilic salts, thus overcoming the Hofmeister series.

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“…. 12 -selective receptors 11 and 12 (Figure 1) and found that the more lipophilic receptor (12) -free receptor by the addition of Ba(NO 3 ) 2 . Macrocycle 12 could also transport SO 4 2À through a bulk chloroform membrane via anion exchange under conditions simulating nuclear waste, demonstrating its potential to application in nuclear-waste treatment.…”

Section: àmentioning

confidence: 96%

Prospects and Challenges in Anion Recognition and Transport

Gilchrist

Gale

2020

Chem

100

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Extraction and transport of sulfate using macrocyclic squaramide receptors

Abstract: Lipophilic macrocycles efficiently extract sulfate ions from water into chloroform and transport this ion across a bulk liquid membrane in the presence of competing anions (chloride, nitrate and dihydrogenphosphate).

Cited by 52 publications

References 51 publications

Cooperative Transport and Selective Extraction of Sulfates by a Squaramide-Based Ion Pair Receptor: A Case of Adaptable Selectivity

Cooperative Transport and Selective Extraction of Sulfates by a Squaramide-Based Ion Pair Receptor: A Case of Adaptable Selectivity

Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

Prospects and Challenges in Anion Recognition and Transport

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