Efficient complexation between pillar[5]arenes and neutral guests: from host–guest chemistry to functional materials

Abstract

Since their discovery in 2008, pillar[n]arenes have been a popular family of macrocyclic arene hosts due to their accessible one-step synthesis, convenient functionalization, symmetrical prism structures and perfect cavity host-guest properties. Compared with other macrocyclic hosts, the most peculiar recognition behavior of pillararenes is the strong binding affinities of pillar[5]arenes (P5As) towards neutral guests in organic media, which is unfeasible for classic crown ethers and calixarenes. The intriguing properties have found extensive applications in many fields from supramolecular chemistry to materials science. This feature article provides a detailed summary of the molecular recognition of P5As and neutral guests, where the driving forces, binding mechanisms, and binding selectivities are comprehensively discussed. Furthermore, brief highlights of research progress in the functional applications based on the neutral guest⊂P5A motifs were also discussed, including the construction of complex topological superstructures (e.g. rotaxanes, catenanes and daisy chains), supramolecular polymers, and functional materials.

Dynamic Hydrogels from Host–Guest Supramolecular Interactions

“…Guest binding by CB[n] macrocycles is much more sensitive to pH change than for CD, with affinity varying over several orders of magnitude depending on protonation of a guest . There is similarly a limited use of pillar[n]arene poly(pseudo)rotaxanes to prepare hydrogels for biomedical applications, with water insolubility of most such macrocycles limiting related efforts primarily to the formation of organogels . Water‐soluble variants, which have been used in creating vesicles and particles for drug delivery, may warrant further exploration in the context of poly(pseudo)rotaxanes.…”

Pillar[5]arene-based amphiphilic supramolecular brush copolymers: fabrication, controllable self-assembly and application in self-imaging targeted drug delivery

“…The driving forces for the formation of P5 ⊃ M were attributed to the cooperativity of hydrophobic interactions and charge transfer interactions between electron-rich P5 and electron-poor M . 11l The formation of 1:1 host–guest complex between P5 and M was further confirmed by a low-resolution electrospray ionization mass spectroscopy peak at m / z 1580.5 (Fig. S11), corresponding to [ P5 ⊃ M – Br – PF 6 ] 2+ .…”

“…9 However, rare examples have been reported using host–guest recognition motifs to fabricate SBPs. Compared with other macrocyclic hosts, such as crown ethers, cyclodextrins, calixarenes, and cucurbiturils, 10 their unique symmetrical structure and easy modification endow pillar[ n ]arenes with superior properties in host–guest recognition, 11 which provide opportunities to construct smart stimuli-responsive SBPs.…”

Gated Materials: Installing Macrocyclic Arenes‐Based Supramolecular Nanovalves on Porous Nanomaterials for Controlled Cargo Release

“…Calixarenes possess a flexible and confirmation changeable calix‐shaped structure with a wider upper rim and a narrow lower rim since their phenolic groups are linked (Figure a) by methylene bridges at meta‐positions, while pillarenes have a relatively rigid pillar‐shaped structure whereas the repeating phenolic units are connected by methylene bridges in the para position . Both macrocyclic arenes have been investigated with much effort and their functionalization and host‐guest properties have been well studied . With all the previous research foundation, supramolecular nanovalves constructed with calixarenes and pillarenes have emerged as powerful machinery on porous solid scaffolds to afford smart controlled release via rational stimulating operations, which comprise divergent external stimuli such as pH, temperature, redox, enzymatic activities, NIR, and competitive binding.…”

“…[26] Both macrocyclic arenes have been investigated with much effort and their functionalization and host-guest properties have been well studied. [27][28][29] With all the previous research foundation, supramolecular nanovalves constructed with calixarenes and pillarenes have emerged as powerful machinery on porous solid scaffolds to afford smart controlled release via rational stimulating operations, which comprise divergent external stimuli such as pH, temperature, redox, enzymatic activities, NIR, and competitive binding. So in this review, we will give a comprehensive introduction on supramolecular nanovalves based on the two typical macrocyclic arenes equipped on solid surfaces of porous nanocarriers, including MSNs, MOFs, core-shell nanomaterials, and rare-earth porous nanomaterials, as well as the operation mechanisms of the nanovalves, mainly developed by our research team.…”