Recognition and separation of sulfate anions

Abstract

This tutorial review focuses on some recent aspects in the development of synthetic receptors for selective sulfate anion recognition and separation, with a special emphasis to: (i) receptors for selective recognition of sulfate in organic and aqueous media and (ii) receptors for separation of sulfate from water via liquid-liquid extraction and crystallization.

Chelate effects in sulfate binding by amide/urea-based ligands

“…4(c)). The other three crystallographicallyindependent (TBA) 2 NH groups closest to the phenyl rings. These ortho-substituted NH groups are pulled in closer by the small bite of the fivemembered ring assisted by the other hydrogen bonded NH groups.…”

“…[1][2][3] One way to attack this problem is to take advantage of extended hydrogen bonding sites, i.e., the chelate effect, in anion host design. In the most favorable scenario this strategy would include not only ligands that are functionalized with the highest possible number of hydrogen bonding sites, but also those that are preorganized in conformations readily positioned for binding a tetrahedral sulfate ion.…”

Nucleic Acid Crystallography

“…Previous protocols in this series described macromolecular refi nement procedures in detail [ 85 ]. Here, we specifi cally report procedures that we routinely use in our lab for refi ning macromolecular structures using Refmac5 [ 61 ] and Phenix [ 63 ].…”

Unique fluoride anion complexation in basic media by 5,5-dioxophenothiazine bis(phenylurea) and bis(phenylthiourea)

“…[4][5][6][7][8][9] One of the main groups of anion receptors consists of neutral molecules having slightly acidic groups, which bind anions by hydrogen bond formation. Examples include amide- [10][11][12] and ureabased [10][11][12][13][14] receptors and host molecules containing heterocycles with slightly acidic NH groups, 11,12,[15][16][17][18] among them bis(phenylureas) and bis(phenylthioureas) having tricyclic heterocyclic units like acridone 17 and carbazole. 18 Increasing the acidity of the sensor molecules can lead to the deprotonation of those in the presence of basic anions (such as fluoride, acetate and dihydrogen phosphate) causing large spectral changes.…”