Unique binding behaviour of water-soluble polycationic oxacalix[4]arene tweezers towards the paraquat dication

Solution- and gas-phase study of binding of ammonium and bisammonium hydrocarbons to oxacalix[4]arene carboxylate

Oxacalixarenes represent a distinctive class of macrocyclic compounds, which are closely related to the parent calixarene family, offering binding motifs characteristic of calixarenes and crown ethers. Nevertheless, they still lack extensive characterization in terms of molecular recognition properties and the subsequent practical applicability. We present here the results of binding studies of an oxacalix[4]arene carboxylate macrocycle toward a variety of organic ammonium cationic species. Our results show that the substituents attached to the guest ammonium compound largely influence the binding strengths of the host. Furthermore, we show that the characteristic binding pattern changes upon transition from the gas phase to solution in terms of the governing intermolecular interactions. We identify the key factors affecting host-guest binding efficacy and suggest rules for the important molecular structural motifs of the interacting parts of ammonium guest species and the macrocycle to facilitate sensing of ammonium cations.

Self-Assembly of Discrete Porphyrin/Calix[4]tube Complexes Promoted by Potassium Ion Encapsulation

The pivotal role played by potassium ions in the noncovalent synthesis of discrete porphyrin-calixarene nanostructures has been examined. The flattened-cone conformation adopted by the two cavities of octa-cationic calix[4]tube C4T was found to prevent the formation of complexes with well-defined stoichiometry between this novel water-soluble calixarene and the tetra-anionic phenylsulfonate porphyrin CuTPPS. Conversely, preorganization of C4T into a C_4v-symmetrical scaffold, triggered by potassium ion encapsulation (C4T@K⁺), allowed us to carry out an efficient hierarchical self-assembly process leading to 2D and 3D nanostructures. The stepwise formation of discrete CuTPPS/C4T@K⁺ noncovalent assemblies, containing up to 33 molecular elements, was conveniently monitored by UV/vis spectroscopy by following the absorbance of the porphyrin Soret band.

Stimuli-Responsive Internally Ion-Paired Supramolecular Polymer Based on a Bis-pillar[5]arene Dicarboxylic Acid Monomer

A novel bis-pillar[5]arene dicarboxylic acid self-assembles in the presence of 1,12-diaminododecane to yield overall neutral, internally ion-paired supramolecular polymers. Their aggregation, binding mode, and morphology can be tuned by external stimuli such as solvent polarity, concentration, and base treatment.

Guest-length driven high fidelity self-sorting in supramolecular capsule formation of calix[5]arenes in water

Only homocapsules 1⊃NC8N⊂1 and 2⊃NC10N⊂2 are selectively formed out of ten potentially different products.

Novel oxacalix[2]arene[2]triazines with thermally activated delayed fluorescence and aggregation-induced emission properties

New kinds of oxacalixarenes based on the triazine moiety have been synthesized, which showed highly twisted conformations and small ΔEST, as well as temperature-dependent transient PL decay curves, indicating the excellent thermally activated delayed fluorescence properties. Moreover, the oxacalixarenes also exhibited apparent aggregation-induced emission properties in THF/H2O mixtures.

Antiadhesive and antibacterial properties of pillar[5]arene-based multilayers

A new type of coating, based on carboxylato-pillar[5]arene/poly(allylamine hydrochloride) multilayer films, for the sustained release of antibiotics with in vitro antiadhesive and antimicrobial activity against Gram-positive and Gram-negative bacteria is described.

Complexation between a triptycene-derived oxacalixarene and π-extended viologens: linker-length-dependent orientation of the macrocycles in pseudo[3]rotaxanes

With an expanded electron-rich cavity and a fixed conformation, macrocycle H was found to encapsulate π-extended viologens G1-G4 to form the first case of pseudo[3]rotaxanes based on oxacalixarenes. The complexation was investigated in detail both in solution and in the solid state using NMR spectroscopy and X-ray crystallography. Due to the three-dimensional nonsymmetric structure of H, three orientational isomers of the pseudorotaxanes could be expected theoretically. However, as the crystal structure analysis revealed, only one of the three isomers was obtained with either G1 or G3. Moreover, with regard to the different lengths of the linkers in the guest molecules, completely opposite orientations of the macrocycles on the axles were observed, which could be explained by different complexation modes between the components in the pseudo[3]rotaxanes. Additionally, the complexation between the host and the guest could be reversibly switched on and off using a suitable acid and base. These results will provide us with the opportunity to design and elaborately regulate high-order molecular devices.

Attraction by repulsion: compounds with like charges undergo self-assembly in water that improves in high salt and persists in real biological fluids

We report a family of highly anionic calixarenes that form discrete homo-dimeric assemblies in pure water, that get stronger in high salt solutions, and that remain assembled in complex, denaturing solutions like real urine. The results reveal the potential of like-charged subunits for self-assembly in high-salt solutions and biological fluids.

Highly selective binding of methyl orange dye by cationic water-soluble pillar[5]arenes

The bulky/negatively charged substituents of guest anions hinder the substrate entering the π-electron rich pillar[5]arene cavity.

A water-soluble hybrid[4]arene: synthesis, host–guest complexation and application in the construction of a supra-amphiphile

A water-soluble hybrid[4]arene was synthesized for the first time and its pH-responsive host–guest complexation with paraquat in water was investigated. This new host–guest recognition motif was further applied in the construction of a supra-amphiphile.