Calix[4, 5]tetrolarenes: A New Family of Macrocycles

Phenacetin[3]Arenes: Mannich-Type Macrocyclization, Unique Structure, Versatile Functionalization, and Strong Allosteric Binding

This work introduces a novel NAm-CH₂-CAr macrocyclization pathway, diverging from the conventional CAr-CH₂-CAr linkages prevalent in macrocyclic arenes. This approach involves a one-pot condensation of - Phenacetin and its homologs with formaldehyde, yielding phenacetin[3]arenes (Ph[3]s) in yields up to 25.9%. Ph[3] exhibits an unsymmetrical hourglass-shaped architecture, featuring an upper rim adorned with amide groups and a lower rim comprising an alkoxylbenzene cavity. This unique structure facilitates reversible equilibrium between conformers via benzene ring flipping, which simultaneously reverses the orientation of amide groups, establishing equilibrium between C3 and F conformers. Increasing concentrations of organic ammonium guests lead to a transition from a predominantly 1:1 to 1:2 host-guest complexation. The estimated binding constants for the 1:1 complexes are in the order of 104-105 M-1, the overall binding constants for the 1:2 complexes are greater than 106 M-2. This stepwise complexation triggers a conformational shift from the C3 to F conformer, demonstrating intriguing allosteric behavior. Furthermore, interactions with chiral guests selectively influence the equilibrium of planar chiral conformers, generating chiroptical responses suitable for chirality sensing applications. The distinct functional groups on the two rims facilitate diverse chemical modifications, including reduction, deprotection, and condensation, providing synthetic flexibility for post-chemical modifications.

Macrocyclic host molecules with aromatic building blocks: the state of the art and progress

Macrocyclic host molecules play the central role in host-guest chemistry and supramolecular chemistry. The highly structural symmetry of macrocyclic host molecules can meet people's pursuit of aesthetics in molecular design, and generally means a balance of design, synthesis, properties and applications. For macrocyclic host molecules with highly symmetrical structures, building blocks, which could be described as repeat units as well, are the most fundamental elements for molecular design. The structural features and recognition ability of macrocyclic host molecules are determined by the building blocks and their connection patterns. Using different building blocks, different macrocyclic host molecules could be designed and synthesized. With decades of developments of host-guest chemistry and supramolecular chemistry, diverse macrocyclic host molecules with different building blocks have been designed and synthesized. Aromatic building blocks are a big family among the various building blocks used in constructing macrocyclic host molecules. In this feature article, the recent developments of macrocyclic host molecules with aromatic building blocks were summarized and discussed.

3,6-Fluoren[5]arenes: synthesis, structure and complexation with fullerenes C60 and C70

3,6-Fluoren[5]arenes with big and rich-electron cavities were conveniently synthesized, which could form stable 1 : 1 complexes with fullerenes in solution.

Selective alkane co-inclusion by methylene- and adamantane-bridged macrocycle with biphenyl units

A methylene- and adamantane-bridged macrocycle with biphenyl units showed selective co-inclusion of n-hexane among the hexane isomers through crystallization. In the use of n-pentane or n-heptane, inclusion crystals with alkanes were not formed.

Elongated-Geminiarene: Syntheses, Solid-State Conformational Investigations, and Application in Aromatics/Cyclic Aliphatics Separation

Energy-saving separation and purification of industrially important compounds with similar physical and chemical properties by novel molecular crystalline materials are of great importance and highly desired. Here a newly enlarged version of geminiarene, namely elongated-geminiarene (ElGA), is first designed and synthesized. Taking advantages of both geminiarenes and biphenarenes, ElGA shows great features including scalable synthesis, nanometer-sized cavity, rich blend of conformational features, and excellent solid-state host-guest properties. Significantly, the functional crystalline materials of ElGA are highly effective in the separation of aromatics and cyclic aliphatics, showing a preference for dimethylbenzene over its corresponding hydrogenation products and paving a new avenue for separation science and industry.

Diffusion NMR for the characterization, in solution, of supramolecular systems based on calixarenes, resorcinarenes, and other macrocyclic arenes

The use of diffusion NMR in studying calixarenes and other arene-based supramolecular systems is described, emphasizing the pivotal role played by the calixarene community in transforming the methods into a routine tool used in supramolecular chemistry.

New opportunities in synthetic macrocyclic arenes

This feature article summarizes the latest research progress in the design and development of new synthetic macrocyclic arenes.

Rational synthesis of benzimidazole[3]arenes by CuII-catalyzed post-macrocyclization transformation

A new series of calix[n]arene analogues, benzimidazole[3]arenes, was rationally synthesized by Cu^II-catalyzed post-macrocyclization transformation of a tris(o-phenylenediamine) macrocycle, and fully characterized by NMR, MS, and single-crystal X-ray diffraction (XRD) analyses.

A new series of calix[n]arene analogues, benzimidazole[3]arenes, was rationally synthesized by Cu^II-catalyzed post-macrocyclization transformation of a tris(o-phenylenediamine) macrocycle, and fully characterized by NMR, MS, and single-crystal X-ray diffraction (XRD) analyses. The resulting syn- and anti-benzimidazole[3]arenes have a bowl-shaped and a warped structure, respectively, in their crystalline states, and both display a dynamic inversion behavior in solution. This modification resulted in strong fluorescence due to the generated benzimidazole moieties. The mechanistic study of the post-macrocyclization transformation demonstrated that the formation of both benzimidazole[3]arenes was catalyzed, via triimine intermediates, by Cu^II ions in air through oxidation and cyclization of the tris(o-phenylenediamine) macrocycle.

Supramolecular Recognition of Three Way Junction DNA by a Cationic Calix[3]carbazole

DNA three-way junctions (TWJ-DNA) are intermediate structures in DNA replication and/or recombination. They play very important roles in biological processes, but more subtle functions are still unknown due partially to the lack of a fluorescent ligand. In this study, a cationic calix[3]carbazole (2) has been synthesized and its properties of interacting with TWJ-DNA have been evaluated by UV/Vis and fluorescence spectroscopy, circular dichroism (CD), gel electrophoresis, and ¹ H NMR studies. The results show that 2 binds to the central hydrophobic cavity of TWJ-DNA. Moreover, it could selectively bind to TWJ-DNA over duplex and quadruplex DNA. Furthermore, 2 possesses the capability of serving as the TWJ-DNA probe as its trap-II excimer emission is turned on by TWJ-DNA.