Supramolecular AA/BB-type oligomer formation from a heterotetratopic bis-calix[5]arene monomer and octanediyldiammonium dichloride

Proton Transfer Mediated Recognition of Amines by Ionizable Macrocyclic Receptors

Ammonium ion/carboxylate ion pairing is a key interaction ubiquitous in biological systems, but amine recognition by ionizable molecular receptors, mediated by host-to-guest proton transfer, has too often been overlooked as...

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.

Tuning the aggregation of an amphiphilic anionic calix[5]arene by selective host–guest interactions with bola-type dications

Bola-type dications of different length drive the formation of head-to-tail or capsular supramolecular amphiphiles and, in turn, that of the final aggregates.

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.

Self-sorting assembly of a calixarene/crown ether polypseudorotaxane gated by ion-pairing

A polypseudorotaxane composed of a calix[5]arene-diammonium supramolecular polymer and dibenzo-24-crown-8 wheels self-assembles only in the presence of superweak counterions

Ring/Chain Morphology Control in Overall-Neutral, Internally Ion-Paired Supramolecular Polymers

The self-assembly of internally ion-paired, neutral AA/BB-type supramolecular polymers composed of complementary di-ionizable homoditopic pairs of monomers is reported. Host-to-guest double-proton transfer mediates the recognition between bis-calix[5]arenedicarboxylic acids and α,ω-diaminoalkanes to yield cyclic, doughnut-shaped assemblies with morphologies (i.e., cyclic vs. linear) that can be controlled by means of external chemical stimuli. The behavior of these intriguing aggregates, both in solution and on surfaces, has been investigated by a combination of ¹ H and DOSY NMR spectroscopy, light-scattering, and atomic force microscopy.

Calix[5]arene Through-the-Annulus Threading of Dialkylammonium Guests Weakly Paired to the TFPB Anion

Through-the-annulus threading of calix[5]arene penta-O-ethers by dialkylammonium cations coupled to the loosely coordinating superweak TFPB^- anion has been achieved. ¹H NMR titration data show that preorganization of the calix[5]arene scaffold leads to great thermodynamic stability of the pseudorotaxane complexes as well as to a favorable threading kinetic. Thus, calix[5]arene 1c, bearing tert-butyl groups at the wide rim, was threaded by all of the cations under study (with the exception of the dibenzylammonium 2b⁺) more tightly than the other derivatives under investigation (K_a's up to 2.02 ± 0.2 × 10⁵ M^-1) because of its preorganized cone conformation. According to DFT calculations, van der Waals interactions between the tert-butyl groups of 1c and the alkyl chain of the cationic axle are likely responsible for the remarkable stability observed. The threading of the calix[5]arene wheels with the asymmetric pentylbenzylammonium axle 2c⁺ led to the toposelective formation of the endo-pentylpseudorotaxane stereoisomer in agreement with the known "endo-alkyl rule". Owing to the steric hindrance of the axle phenyl group, the threading of the guest was seen to occur in a unidirectional fashion through the calixarene narrow rim.

Self-healing polymer materials constructed by macrocycle-based host-guest interactions

Self-healing polymers, which can spontaneously recover themselves after being ruptured, result in enhanced lifetimes for materials and open up a fascinating direction in material science. Macrocycle-based host-guest interactions, one of the most crucial non-covalent interactions, play a key role in self-healing material fabrication. This review aims to highlight the very recent and important progress made in the area of self-healing polymer materials by focusing on cyclodextrins (CDs), crown ethers, cucurbit[n]urils (CBs), calix[n]arenes and pillar[n]arenes with special guest groups and tailored structures. In addition, we also propose future research directions and hope that this review can in a way reflect the current situation and future trends in this developing area.

Selective recognition of biogenic amine hydrochlorides by heteroditopic dihomooxacalix[4]arenes

New receptors for the selective binding of monoamine neurotransmitters and trace amine hydrochlorides, as ion pairs, are described.

Probing the inner space of salt-bridged calix[5]arene capsules

A combined DOSY and XRD study indicates that a carboxylcalix[5]arene receptor is able to encapsulate α,ω-diamines of appropriate length by means of a proton-transfer-mediated recognition process followed by salt-bridge-assisted bis-endo-complexation.