Surprisingly High Selectivity and High Affinity in Mercury Recognition by H-Bonded Cavity-Containing Aromatic Foldarands.
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 Hg2+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 Hg2+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 Hg2+ions. With a [4]:[Hg2+] molar ratio of 5:1 and a single biphasic solvent extraction, the concentration of Hg2+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]:[Hg2+] molar ratio.
Institute of Bioengineering and Nanotechnology , 31 Biopolis Way, The Nanos, Singapore 138669.
Jie
J
Shen
Institute of Bioengineering and Nanotechnology , 31 Biopolis Way, The Nanos, Singapore 138669.
Changliang
C
Ren
Institute of Bioengineering and Nanotechnology , 31 Biopolis Way, The Nanos, Singapore 138669.
Huaqiang
0000-0002-8246-2000
H
Zeng