Encapsulation and selective recognition of sulfate anion in an azamacrocycle in water

Abstract

Structural characterization of a sulfate complex with an azamacrocycle suggests that one sulfate is encapsulated in the macrocyclic cavity with eight hydrogen bonds; a significant selectivity of the host was observed for sulfate over halides, nitrate and perchlorate as evaluated by 1 H NMR studies in water.Sulfate is present in the biological system and plays a crucial role in many biochemical processes, 1 such as in biosynthesis 2 and sulfate binding proteins. 3 Sulfate is also a known inorganic pollutant in the environment. 4 For example, contamination of the Hanford nuclear waste site by this anion has been a matter of increased concern, hampering the vitrification process. 5 However, as compared to other oxoanions, such as phosphate and nitrate, this anion has been less studied with synthetic hosts. 6 Therefore, the design of suitable hosts for selective recognition of sulfate remains a challenge in the area of anion binding chemistry. 7 Encapsulated sulfate was crystallographically characterized in self-assembled metal-organic cage hosts, polyamides, 8 ureas 9 or indoles. 10 In these cases, an encapsulation occurred within the crystal lattices formed by a host matrix or between hosts. Based on the theoretical † Electronic supplementary information (ESI) available: One crystallographic data in CIF format, the synthetic procedure in pdf format. CCDC 777812. For ESI and crystallographic data in CIF or other electronic format see

Colorimetric and optical discrimination of halides by a simple chemosensor

“…Kavallieratos and coworkers used an APCI-MS (atmospheric pressure chemical ionization mass spectrometry) for the detection of halides and nitrate with sulfonamides in dichloromethane. 39 Our group recently used ESI-MS to probe a sulfate complex with a thiophene-based monocycle 40 and an octameric phosphate cluster with a tren-based amine. 41 This is a direct method to examine the stability and stoichiometry of a complex in a gaseous state.…”

Solution and structural binding studies of phosphate with thiophene-based azamacrocycles

“…As a result, the monohydrogen phosphate is closer to the cavity than the dihydrogen phosphate. The involvement of CH···O interactions is well documented in the literature [21]. Extensive hydrogen bonds between the macrocycle and water molecules are also present.…”

“…Other reported receptors that are neutral molecules including amides [13], thioamides [14], ureas [15], thioureas [16], pyrroles [17] and indoles [18] were shown to bind phosphate in organic solvents. Our recent studies on various macrocycle-based receptors indicated that hydrogen bonding and electrostatic interactions are major binding forces in stabilizing complexes; thus providing insight into the binding modes of anions and conformations of host molecules [19-21]. Herein, we report the binding aspects of two thiophene-based macrocycles L1 and L2 via 1 H NMR and 31 P NMR in solutions.…”

Encapsulation and selectivity of sulfate with a furan-based hexaazamacrocyclic receptor in water

“…9 The first encapsulated sulfate with a polyammonium-based host was reported in 2005, where the sulfate was held within the cavity of a m -xylyl-based cryptand via five NH⋯O bonds. 9a Recently, there have been reported several types of neutral hosts including metal–organic cage hosts, 10 polyamides, 11 ureas, 12 thioureas, 13 and indoles; 14 which provide remarkable selectivity and binding affinity for sulfate in organic solvents. For example, Loeb et al reported an encapsulated sulfate within a metal-organic framework containing urea-functionalized quinoline ligands.…”