Li-Li Tan

Viologen-Mediated Assembly of and Sensing with Carboxylatopillar[5]arene-Modified Gold Nanoparticles

Carboxylatopillar[5]arene (CP[5]A), a new water-soluble macrocyclic synthetic receptor, has been employed as a stabilizing ligand for in situ preparation of gold nanoparticles (AuNPs) to gain new insights into supramolecular host-AuNP interactions. CP[5]A-modified AuNPs with good dispersion and narrow size distributions (3.1 ± 0.5 nm) were successfully produced in aqueous solution, suggesting a green synthetic pathway for the application of AuNPs in biological systems. Supramolecular self-assembly of CP[5]A-modified AuNPs mediated by suitable guest molecules was also investigated, indicating that the new hybrid material is useful for sensing and detection of the herbicide paraquat.

Near-infrared light-responsive supramolecular nanovalve based on mesoporous silica-coated gold nanorods

We constructed a novel cancer theranostic hybrid platform, based on mesoporous silica-coated gold nanorods (AuNR@MSN) gated by sulfonatocalix[4]arene (SC[4]A) switches, for bio-friendly near-infrared (NIR) light-triggered cargo release in a remote and stepwise fashion. The advantages of supramolecular switches, mesoporous silicas, and AuNRs were combined in one drug delivery system. Mesoporous silicas coated on AuNRs guarantee a high drug payload and can be easily post-functionalized. Significantly, the plasmonic heating from the NIR light-stimulated AuNR cores can decrease the ring-stalk binding affinity, leading to the dissociation of SC[4]A rings from the stalks, thus opening the nanovalves and releasing the cargos. The NIR light-responsive mechanized AuNR@MSN offers exciting prospects for non-invasive controlled drug delivery, being more effective and safer than other techniques.

Pillar[5]arene‐Based Supramolecular Organic Frameworks for Highly Selective CO2‐Capture at Ambient Conditions

Low-density, solid-state, porous supramolecular organic frameworks are constructed using pillarenes. The frameworks have a honeycomb-like structure, permanent porosity, high thermal stability, and selective and reversible sorption properties toward CO2. The exceptionally selective CO2-sorption properties (375/1, 339/1) of one framework over N2 and CH4 indicate potential applications in CO2-capture for post-combustion power plants and natural gas sweetening.

Acetylcholine-triggered cargo release from supramolecular nanovalves based on different macrocyclic receptors.

Acetylcholine (ACh), a neurotransmitter located in cholinergic synapses, can trigger cargo release from mesoporous silica nanoparticles equipped with calixarene- or pillarene-based nanovalves by removing macrocycles from the stalk components. The amount and speed of cargo release can be controlled by varying the concentration of ACh in solution or changing the type of gating macrocycle. Although this proof-of-concept study is far from a real-life application, it provides a possible route to treat diseases related to the central nervous system.

Zn2+-Triggered Drug Release from Biocompatible Zirconium MOFs Equipped with Supramolecular Gates

A new theranostic nanoplatform, comprising of monodisperse zirconium metal-organic frameworks (MOFs) as drug carriers and carboxylatopillar[5]arene-based supramolecular switches as gating entities, is constructed, and controlled drug release triggered by bio-friendly Zn(2+) ions (abundant in synaptic vesicles) and auxiliary thermal stimulus is realized. This on-command drug delivery system exhibits large pore sizes for drug encapsulation, excellent biodegradability and biocompatibility, extremely low cytotoxicity and premature drug release, and superior dual-stimuli responsiveness, opening a new avenue in targeted drug delivery and controlled release of therapeutic agents, especially in the treatment of central nervous system diseases.

Molecular recognition and self-assembly of pillarenes

As a rapidly developing class of synthetic macrocycles with intrinsic characteristics and properties, pillarenes (or pillararenes) have become more and more attractive on account of their unique features and potentials in fabricating functional materials. This feature article provides an overview of molecular recognition and self-assembly of pillarenes. The host–guest motifs, building strategies, topological architectures, stimuli-responsiveness, functionalities and various supramolecular assemblies including mechanically interlocked molecules containing rotaxanes, polyrotaxanes and catenanes, self-inclusion complexes, supramolecular dimers and polymers, micelles, vesicles, tubes and artificial transmembrane channels are comprehensively discussed. Prospects about future research directions and applications in this research area are predicted.

Selective recognition of “solvent” molecules in solution and the solid state by 1,4-dimethoxypillar[5]arene driven by attractive forces

Highly selective binding of “solvent” molecules by 1,4-dimethoxypillar[5]arene (DMP[5]A) and their host–guest complexation in solution and the solid state have been investigated by multiple methods. Enthalpy changes and the size-fit effect play an important role in the high selectivity.

Smart mesoporous silica nanoparticles gated by pillararene-modified gold nanoparticles for on-demand cargo release.

A new drug delivery system, based on mesoporous silica nanoparticles gated by carboxylatopillar[5]arene-modified gold nanoparticles, has been fabricated, which demonstrated good responses to competitive binding and temperature variation. This multifunctional nanosystem combines the excellent characteristics of two kinds of nanoparticles and utilizes a supramolecular host-guest approach for on-demand cargo release.

Highly CO2 selective pillar[n]arene-based supramolecular organic frameworks

Abstract Finding a cost-effective, environmental benign, economical and technologically viable way to selectively capture, storage and/or purify energy and light gases represents one of the most urgent needs from energetic, biological, and environmental standpoints. Two 3D low-density supramolecular organic frameworks (SOFs) with solution-processibility were constructed using low-cost and readily available synthetic macrocyclic compounds, namely pillar[5]arene (P5) and pillar[6]arene (P6), via strong O-H···O, C-H···O, C-H···π, π···π interactions. These SOFs offer unusual topology, interconnecting pores and extremely high selective CO2 capture and separation properties for multiple gas mixtures (e.g. 30/70 mixture of CO2/H2, up to 3733/1, 298 K), making them great promising candidates for practical gas separation of steam-methane re-former (SMR) off-gas, flue gas, natural gas, biogas, syngas, paraffin/olefin, etc.

Calixarenes and Pillarenes on Surfaces

The present chapter reports on recent developments of calixarenes and pillarenes (or pillar[n]arenes) on the surfaces of a variety of different nanoparticles (i.e., gold, silver, quantum dots, Fe3O4, TiO2, Pt, Pd, and Ru), electrodes, devices, porous materials (i.e., mesoporous silica and metal-organic frameworks), and carbon materials. Compared with traditional hybrid materials, these hybrid organic-inorganic nanosystems take advantage of molecular recognition of calixarenes and pillarenes towards guests for the fabrication of nanodevices of nano-micro sizes with optical, mechanical, electrical, catalytic and electrochemical properties. Their splendid applications in recognition, stabilization, self-assembly, dispersion, electrode, controlled drug release, separation and absorption will be covered in this chapter.