Synthesis, structure and binding properties of a series of dissymmetric resorcin[4]arene-based cavitands

The Versatile Applications of Calix[4]resorcinarene-Based Cavitands

The advancement of synthetic host-guest chemistry has played a pivotal role in exploring and quantifying weak non-covalent interactions, unraveling the intricacies of molecular recognition in both chemical and biological systems. Macrocycles, particularly calix[4]resorcinarene-based cavitands, have demonstrated significant utility in receptor design, facilitating the creation of intricately organized architectures. Within the realm of macrocycles, these cavitands stand out as privileged scaffolds owing to their synthetic adaptability, excellent topological structures, and unique recognition properties. So far, extensive investigations have been conducted on various applications of calix[4]resorcinarene-based cavitands. In this review, we will elaborate on their diverse functions, including catalysis, separation and purification, polymeric materials, sensing, battery materials, as well as drug delivery. This review aims to provide a holistic understanding of the multifaceted roles of calix[4]resorcinarene-based cavitands across various applications, shedding light on their contributions to advancing the field of supramolecular chemistry.

Sodium cation-templated synthesis of an ion-pair binding heteroditopic [2]catenane

A novel method utilising sodium cation templation between a pyridinium bridged calix[4]diquinone macrocycle and a pyridine-N-oxide functionalised macrocycle precursor motif is used for the construction of a mechanically interlocked ion-pair.

Polymerized Molecular Receptors as Adsorbents to Remove Micropollutants from Water

Organic micropollutants (MPs) are increasing in number and concentration in water systems as a result of human activities. Often from human origin, these micropollutants build up in the environment because organisms lack the mechanisms to metabolize these substances, which cause negative health, ecological, and economic effects. Adsorption-based remediation processes for these compounds often rely on activated carbon materials. However, activated carbons are ineffective against certain MPs, exhibit low removal efficiencies in the presence of common aqueous matrix constituents, and require energy-intensive activation and regeneration processes. To overcome the deficiencies of traditional technologies, novel adsorbents based on molecular receptors offer promising alternative solutions. This Account describes the recent development of polymer adsorbents based on molecular receptors for removing trace organic chemicals from water. Polymer networks based on molecular receptors have high binding affinities for many MPs but, unlike activated carbons, have a specific molecule-binding mechanism that prevents these polymers from being fouled by matrix constituents such as natural organic matter. The size and hydrophobic pocket of the β-cyclodextrin receptor preferentially adsorbs target molecules such as organic micropollutants in the presence of matrix constituents, and the nature of the cross-linker tunes the binding affinity and selectivity of the adsorbent for specific classes of MPs, including those of varying charge and hydrophobicity. β-cyclodextrin polymers also exhibit rapid adsorption kinetics and are easily regenerated. This Account details β-cyclodextrin polymers made with three different cross-linkers, including a polymer that is postsynthetically transformed from a negatively charged polymer to a positively charged polymer to invert the polymer's micropollutant adsorption profile. Morphological constraints have so far limited these cross-linked polymers' ability to be used in commercial applications, but two methods to create larger and more uniformly sized particles for use in flow-through applications are described here. β-Cyclodextrin polymers are useful for trapping organic micropollutants such as bisphenol A, perfluorooctanoic acid, and many kinds of pharmaceuticals and pesticides, but their binding pockets are too large to capture micropollutants that are small or of high polarity. Other molecular receptors such as resorcinarene cavitands can target lower-molecular-weight MPs, including halomethane disinfection byproducts and industrial solvents, that are not bound strongly by β-cyclodextrins. These materials demonstrate the potential of expanding the library of polymers based on molecular receptors. Overall, these emerging adsorbents show promise for the removal of legacy and emerging MPs from water, as well as the ability to rationally tune the adsorbent's structure to target the most persistent and toxic MPs.

One-Step Synthesis of C2v-Symmetric Resorcin[4]arene Tetraethers

The three-component reaction between a resorcinol, 1,3-dimethoxybenzene, and an alkyl aldehyde (R = C₁-C₁₁) along with BF₃·OEt₂ affords a C_2v-symmetric resorcin[4]arene tetraether in one step; in most cases, the single isomer can be precipitated from the reaction mixture in moderate to excellent yields (up to 89%). The reaction is tolerant of 2-substituted resorcinols (R' = OH, Cl, Br, Me), allowing a third type of functionality to be regioselectively incorporated during the macrocyclization.