Surprisingly High Selectivity and High Affinity in Mercury Recognition by H-Bonded Cavity-Containing Aromatic Foldarands

Abstract

In the absence of macrocyclic ring constraints, few synthetic systems, possessing a mostly solvent-independent well-folded conformation that is predisposed for highly selective and high affinity recognition of metal ions, have been demonstrated. We report here such a unique class of conformationally robust modularly tunable folding molecules termed foldarands that can recognize Hg ions surprisingly well over 22 other metal ions. Despite the lack of sulfur atoms and having only oxygen-donor atoms in its structure, the best foldarand molecule, i.e., tetramer 4, exhibits a selectivity factor of at least 19 in differentiating the most tightly bound Hg ion from all other metal ions, and a binding capacity that is ≥18 times that of thio-crown ethers. These two noteworthy binding characters make possible low level removal of Hg ions. With a [4]:[Hg] molar ratio of 5:1 and a single biphasic solvent extraction, the concentration of Hg ions could be reduced drastically by 98% (from 200 to 4 ppb) in pure water. 4 could also effect a highly efficient reduction in mercury content by 98% (from 500 to 10 ppb) in artificial groundwater via multiple successive extractions with an overall consumption of 4 being 9:1 in terms of [4]:[Hg] molar ratio.

A Foldamer-Based Organocatalyst for Direct Arylations of Unactivated Arenes

“…Interestingly, these acyclic foldamer molecules also exhibit good binding toward the K + ion. 5 Given the similarities in structure and in potassium binding between cyclic P5b and acyclic F1−F5, we believed F1−F5 might be capable of performing similar catalytic functions. We therefore decided to investigate the possible use of these acyclic foldamers to catalyze direct arylations of unactivated arenes with aryl halides in the absence of transition metals.…”

“…We then further investigated the reactions using different bases (e.g., t-BuOLi, t-BuONa, and KOH) and found that no product could be obtained under the same conditions using F2 as the catalyst (entries 7−9, Table 1). Given the fact that F2 binds K + more strongly than Na + or Li + , 5 these results indicate that a stronger base (t-BuO − vs OH − ) and availability of such a base (e.g., t-BuO − ) in solution via potassium chelation by the ligand are critically important to drive the reaction to completion.…”

Function Led Design of Aerogels: One-pot Self-assembly of 3D Macroscope Poly(vinyl alcohol) Aerogel for Mercury Species Removal in Aqueous Solution with Super-Fast Regeneration

“…The most commonly used donor atoms include N, S and O and the groups containing them involve (for N) azoic compound, amines, acidamide, azo groups or nitriles, (for S) thioalcohols, sulfoethers, or thiocarbamic acid esters, (for O) carboxyls, hydroxyls, phenols, ethers, carbonyls or phosphoryl groups. Previous studies have already illustrated the high speci city of phytate in sequestering Hg 2+ ions (De Stefano et al 2006), and the combination between carbonyls and Hg 2+ has high idiosyncrasy (Ermakova et al 2013, Shen et al 2017). In our study, despite the absorbent is nitrogen-and sulfur-free, the PA molecules provide su cient phosphoryl groups that can e ciently bind with Hg 2+ , even in the presence of some competing heavy metal ions (Mn 2+ , Cd 2+ , Cr 2+ , Cu 2+ and Pb 2+ ) (A/S ratio of 4.1 g L -1 ) (Table 3).…”

Shaping Macromolecules for Sensing Applications—From Polymer Hydrogels to Foldamers

“…The large library of structural motifs of foldamers enables the design of countless functions and applications [ 174 , 175 , 176 ], including sensing [ 151 , 177 ]. Thanks to the structural control of foldamers, they can be designed to bind complementary guests [ 178 ], e.g., cations [ 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 ], anions [ 186 , 187 , 188 , 189 , 190 , 191 , 192 ], or non-charged molecules [ 164 , 193 , 194 , 195 , 196 , 197 , 198 , 199 , 200 , 201 , 202 , 203 , 204 , 205 , 206 , 207 , 208 , 209 ]. They have been applied in the detection of metal ions [ 210 , 211 , 212 , 213 ], explosives [ 214 ], biomarkers [ 215 ], pH [ 216 , 217 ], membrane curvature [ 218 ], and fructose [ 198 ] ( Table 3 ).…”