One-Pot Synthesis of Strained Macrocyclic Pyridone Hexamers and Their High Selectivity toward Cu²⁺ Recognition

The removal of Cu²⁺ ions is relevant to environmental pollution control and neurodegenerative disease treatment. A novel family of strained macrocyclic pyridone hexamers, which exhibit highly selective recognition of Cu²⁺ ions and reduce copper content in artificial seawater by 97% at a very low [host]:[CuCl₂] molar ratio of 2:1, is documented

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 <b>4</b>, 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 [<b>4</b>]:[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. <b>4</b> 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 <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg²⁺] molar ratio

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 <b>4</b>, 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 [<b>4</b>]:[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. <b>4</b> 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 <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg²⁺] molar ratio

Intramolecularly Hydrogen-Bonded Aromatic Pentamers as Modularly Tunable Macrocyclic Receptors for Selective Recognition of Metal Ions

Despite the tremendous progress that has been made in macrocyclic chemistry since the discovery of corands, cryptands, and spherands more than four decades ago, macrocyclic systems possessing a high level of controllability in structural configuration concurrent with a systematic tunability in function are still very rare. Employing an inner design strategy to orient H-bonding forces toward a macrocyclic cavity interior while convergently aligning exchangeable ion-binding building blocks that dictate a near-identical backbone curvature, we demonstrate here a novel pentagonal framework that not only enables its variable interior cavity to be maintained at near-planarity but also allows its ion-binding potential to be highly tunable. The H-bonded macrocyclic pentamers thus produced have allowed a systematic and combinatorial evolution of ion-selective pentamers for preferential recognition of Cs⁺, K⁺, or Ag⁺ ions

Low-Cost Phase-Selective Organogelators for Rapid Gelation of Crude Oils at Room Temperature

Frequent marine oil spills pose a significant threat to the environment and marine’s ecosystem. We have recently reported a highly tunable molecular gelling scaffold, which enables us to identify a few first examples of phase-selective organogelators (PSOGs) that can instantly gel the crude oil of various types with room-temperature operation. In this study, we demonstrate the high robustness and reliability of this modular gelling scaffold in consistently and combinatorially producing high capacity PSOGs. Such a unique feature has allowed us to carry out a systematic study of 48 gelators via a two-step screening process and to discover another powerful carboxybenzyl-based gelator with comparable gelling properties but with a cost lowered by more than 300%, pointing to a good commercial potential for rapid cleanup of oil spills while effectively eliminating environmental pollution caused by the spilled oil

Pore-Forming Monopeptides as Exceptionally Active Anion Channels

We describe here a unique family of pore-forming anion-transporting peptides possessing a single-amino-acid-derived peptidic backbone that is the shortest among natural and synthetic pore-forming peptides. These monopeptides with built-in H-bonding capacity self-assemble into an H-bonded 1D columnar structure, presenting three types of exteriorly arranged hydrophobic side chains that closely mimic the overall topology of an α-helix. Dynamic interactions among these side chains and membrane lipids proceed in a way likely similar to how α-helix bundle is formed. This subsequently enables oligomerization of these rod-like structures to form ring-shaped ensembles of varying sizes with a pore size of smaller than 1.0 nm in diameter but sufficiently large for transporting anions across the membrane. The intrinsic high modularity in the backbone further allows rapid tuning in side chains for combinatorial optimization of channel’s ion-transport activity, culminating in the discovery of an exceptionally active anion-transporting monopeptide <b>6L10</b> with an EC₅₀ of 0.10 μM for nitrate anions

Instant Room-Temperature Gelation of Crude Oil by Chiral Organogelators

Large-scale treatment of oily water arising from frequent marine oil spills presents a major challenge to scientists and engineers. Although the recently emerged phase-selective organogelators (PSOG) do offer very best promises for oil spill treatment, there still exists a number of technical barriers to overcome collectively, including gelators’ high solubility, high gelling ability, general applicability toward crude oil of various types, rapid gelation with room temperature operation, low toxicity, and low cost. Here, a denovo-designed unusually robust molecular gelling scaffold is used for facile construction of a PSOG library and for rapid identification of PSOGs with the most sought-after practical traits. The identified gelators concurrently overcome the existing technical hurdles, and for the first time enable instant room-temperature gelation of crude oil of various types in the presence of seawater. Remarkably, these excellent gelations were achieved with the use of only 0.058–0.18 L of environmentally benign carrier solvents and 7–35 g of gelator per liter of crude oil. Significantly, 2 out of 20 gelators could further congeal crude oil in the powder form at room temperature, highlighting another excellent potential of the developed modularly tunable system in searching for more powerful powder-based gelators for oil spill treatment

An Artificial Tongue Fluorescent Sensor Array for Identification and Quantitation of Various Heavy Metal Ions

Herein, a small-molecule fluorescent sensor array for rapid identification of seven heavy metal ions was designed and synthesized, with its sensing mechanism mimicking that of a tongue. The photoinduced electron transfer and intramolecular charge transfer mechanism result in combinatorial interactions between sensor array and heavy metal ions, which lead to diversified fluorescence wavelength shifts and emission intensity changes. Upon principle component analysis (PCA), this result renders clear identification of each heavy metal ion on a 3D spatial dispersion graph. Further exploration provides a concentration-dependent pattern, allowing both qualitative and quantitative measurements of heavy metal ions. On the basis of this information, a “safe-zone” concept was proposed, which provides rapid exclusion of versatile hazardous species from clean water samples based on toxicity characteristic leaching procedure standards. This type of small-molecule fluorescent sensor array could open a new avenue for multiple heavy metal ion detection and simplified water quality analysis