Supramolecular chemistry of liquid-liquid extraction

Liquid-Liquid Extraction (LLE) is a venerable and widely used method for the separation of a targeted solute between two immiscible liquids. In recent years, this method has gained popularity in the supramolecular chemistry community due to the development of various types of synthetic receptors that effectively and selectively bind specific guests in an aqueous medium through different supramolecular interactions. This has eventually led to the development of state-of-the-art extraction technologies for the removal and purification of anions, cations, ion pairs, and small molecules from one liquid phase to another liquid phase, which is an industrially viable method. The focus of this perspective is to furnish a vivid picture of the current understanding of supramolecular interaction-based LLE chemistry. This will not only help to improve separation technology in the chemical, mining, nuclear waste treatment, and medicinal chemistry sectors but is also useful to address the purity issue of the extractable species, which is otherwise difficult. Thus, up-to-date knowledge on this subject will eventually provide opportunities to develop large-scale waste remediation processes and metallurgy applications that can address important real-life problems.

Finding a receptor design for selective recognition of perrhenate and pertechnetate: hydrogen vs. halogen bonding

Receptors bearing hydrogen and halogen bond donor sites for recognition of perrhenate and pertechnetate were designed and studied.

Catching the chloride: searching for non-Hofmeister selectivity behavior in systematically varied polyamide macrocyclic receptors

Searching for regularities in the large set of structurally diverse macrocyclic probes allowed us to determine the structural requirements for the selective recognition of chloride over more basic anions such as H₂PO₄⁻ or RCO₂⁻ by a putative anion receptor.

A high-yield synthesis and acid–base response of phosphate-templated [3]rotaxanes

We show a high-yielding synthesis (80%) of [3]rotaxanes using shape-persistent macrocycles, cyanostars, and anionic organo-phosphate templates catalyzed by low steric-demand click chemistry.

Size-matched recognition of large anions by cyanostar macrocycles is saved when solvent-bias is avoided

A bulky cyanostar that only forms 1 : 1 complexes was created to study the poorly understood size dependent recognition of large anions by shape-persistent macrocycles.

Solution and solid-phase halogen and C-H hydrogen bonding to perrhenate

(1)H NMR spectroscopic and X-ray crystallographic investigations of a 1,3-bis(4-ethynyl-3-iodopyridinium)benzene scaffold with perrhenate reveal strong halogen bonding in solution, and bidentate association in the solid state. A nearly isostructural host molecule demonstrates significant C-H hydrogen bonding to perrhenate in the same phases.

Fluorescent sensing of 99Tc pertechnetate in water

The fluorescent cage senses pertechnetate in water at μM concentration, opening perspectives to detect the pollutant without radioanalytical instrumentation.