Anion complexation and sensing using modified urea and thiourea-based receptors

Abstract

This critical review highlights recent advances in the structurally modified (thio)urea-based receptors for anion complexation and sensing. Modifications of the (thio)urea structure are aimed at a better anion binding in terms of higher binding constant, anion selectivity and feasibility. Major (thio)urea receptors are reviewed as N-alkyl, N-aryl and N-amido/N-amino (thio)ureas. Hints for designing (thio)urea-based receptors for anions are discussed (102 references).

Sensing mechanism for a fluoride chemosensor: invalidity of excited-state proton transfer mechanism

“…4 Given that fluorescent chemosensors have apparent advantages, such as operational simplicity, low cost, high sensitivity, high selectivity, and rapid implementation, 5 intensive investigations are largely focused on developing fluorescent chemosensors for fluoride anions. 6,7 Among the developed fluorescent chemosensors, those with tert-butyldimethylsilyl (TBDMS) and tert-butyldiphenylsilyl (TBDPS) exhibit higher selectivity and stability. This type of chemosensor was first reported by Kim and Swager, 8 and belongs to the reaction-based type.…”

Urea-cored peptides for anion binding and vesicle formation

“…A variety of receptors containing a urea motif have been developed and studied for their anion sensing. [13][14][15][16][17] Therefore, the urea unit has been taken as an excellent motif for the construction of anion receptors. The success of urea as a binding motif is due to the fact that it possesses two close N-H units that can chelate a spherical anion in bifurcate hydrogen bonding mode, giving rise to a six-membered ring ( Figure 1a).…”

Thermodynamics of Complexation between Thiourea-based Receptor and Acetate in Water/Acetonitrile Mixture

“…[1][2][3][4][5][6] The binding properties of a monothiourea-based receptor are primarily governed by the electrostatic interaction between the anion and the monothiourea group, and the binding constant of a monothiourea-based receptor decreases with decreasing intrinsic anion basicity. The monothiourea-based receptor has thus been utilized for selective recognition of acetate (MeCO2 -) and fluoride (F -) ions in organic solvents 7 and water/organic solvent mixtures.…”

“…1). [1][2][3][4][5][6] Since the complex formation is strongly inhibited by hydration of both receptor and anion, thiourea-based receptors have usually been examined in organic solvents 7 or water/ organic solvent mixtures. 8 In thermodynamic studies of ureaand thiourea-based receptors in organic solvents such as acetonitrile (MeCN), 10 dimethyl sulfoxide (DMSO), [11][12][13][14] and chloroform, 13 complex formation is usually reported to be an exothermic and enthalpy-driven reaction.…”