Dimeric Pillar[5]arene as a Novel Fluorescent Host for Controllable Fabrication of Supramolecular Assemblies and Their Photocatalytic Applications

Perphenazine modified pillar[5]arene based nano-assemblies for synergistic photothermal and photodynamic cancer therapy

Nano-assemblies based on perphenazine modified pillar[5]arene were constructed successfully for synergistic photothermal and photodynamic (I&II) cancer therapy.

Organic Donor-Acceptor Systems for Photocatalysis

Organic semiconductor materials are considered to be promising photocatalysts due to their excellent light absorption by chromophores, easy molecular structure tuning, and solution-processable properties. In particular, donor-acceptor (D-A) type organic photocatalytic materials synthesized by introducing D and A units intra- or intermolecularly, have made great progress in photocatalytic studies. More and more studies have demonstrated that the D-A type organic photocatalytic materials combine effective carrier separation, tunable bandgap, and sensitive optoelectronic response, and are considered to be an effective strategy for enhancing light absorption, improving exciton dissociation, and optimizing carrier transport. This review provides a thorough overview of D-A strategies aimed at optimizing the photocatalytic performance of organic semiconductors. Initially, essential methods for modifying organic photocatalytic materials, such as interface engineering, crystal engineering, and interaction modulation, are briefly discussed. Subsequently, the review delves into various organic photocatalytic materials based on intramolecular and intermolecular D-A interactions, encompassing small molecules, conjugated polymers, crystalline polymers, supramolecules, and organic heterojunctions. Meanwhile, the energy band structures, exciton dynamics, and redox-active sites of D-A type organic photocatalytic materials under different bonding modes are discussed. Finally, the review highlights the advanced applications of organic photocatalystsand outlines prospective challenges and opportunities.

FRET-Based Host-Guest Supramolecular Probe for On-Site and Broad-Spectrum Detection of Pyrethroids in the Environment

The massive use of pyrethroid pesticides in agriculture has brought growing concerns about food safety due to their several harmful effects on human health, especially through the accumulation of the food chain. To date, most of the available analytical methods for pyrethroids still suffer from insufficient detection universality, complicated sample pretreatment, and detection processes, which severely limit their practical applications. Herein, a novel Förster resonance energy transfer (FRET)-assisted host-guest supramolecular nanoassembly is reported, for the first time, successfully realizing ratiometric fluorescent detection of pyrethroids in real samples through the indicator displacement assay (IDA) mechanism. This method is capable of detecting a broad spectrum of pyrethroids, including bifenthrin, cyfluthrin, cypermethrin, deltamethrin, etofenprox, fenvalerate, and permethrin, with ultrahigh detection sensitivity, great selectivity, high anti-interference ability, and, in particular, distinct emission color response from red to green. Such a large chromatic response makes this method available for fast and on-site detection of pyrethroids in real samples with the aid of several simple portable analytical apparatuses.

Friedel-Crafts Acylation for Accessing Multi-Bridge-Functionalized Large Pillar[n]arenes

Pillar[n]arenes can be constructed using a Friedel-Crafts alkylation process. However, due to the reversible nature of the alkylation, mixture of large pillar[n]arenes (n≥7) are obtained as minor products, and thus laborious purification are necessary to isolate the larger pillar[n]arenes. Moreover, inert methylene bridges are introduced during the alkylation process, and the multi-functionalization of the bridges has never been investigated. Herein, an irreversible Friedel-Crafts acylation is used to prepare pillar[n]arenes. Due to the irreversible nature of the acylation, the reaction of precursors bearing carboxylic acids and electron-rich arene rings results in a size-exclusive formation of pillar[n]arenes, in which the ring-size is determined by the precursor length. Because of this size-selective formation, laborious separation of undesired macrocycles is not necessary. Moreover, the bridges of pillar[n]arenes are selectively installed with reactive carbonyl groups using the acylation method, whose positions are determined by the precursor used. The carbonyl bridges can be easily converted into versatile functional groups, leading to various laterally modified pillar[n]arenes, which cannot be accessed by the alkylation strategy.

Stereoselective Single Step Cyclization to Give Belt-Functionalized Pillar[6]arenes

Two macrocycles were synthesized through cyclization reactions of secondary benzylic alcohols, giving pillar[6]arenes with a methyl substituent at each belt position. These macrocycles form stereoselectively with only the rtctct isomer with alternating up and down orientations of the belt methyl groups definitively identified. Isolated yields were modest (7 and 9%), but the macrocycles are prepared in a single step from either a commercially available alcohol or a very readily prepared precursor. X-ray crystal structures of the macrocycles indicate they have a capsule-like structure, which is far from the conventional pillar shape. Density functional theory calculations reveal that the energy barrier required to obtain the pillar conformation is significantly higher for these belt-functionalized macrocycles than for conventional belt-unfunctionalized pillar[6]arenes.

Applications of Supramolecular Polymers Generated from Pillar[n]arene-Based Molecules

Supramolecular chemistry enables the manipulation of functional components on a molecular scale, facilitating a "bottom-up" approach to govern the sizes and structures of supramolecular materials. Using dynamic non-covalent interactions, supramolecular polymers can create materials with reversible and degradable characteristics and the abilities to self-heal and respond to external stimuli. Pillar[n]arene represents a novel class of macrocyclic hosts, emerging after cyclodextrins, crown ethers, calixarenes, and cucurbiturils. Its significance lies in its distinctive structure, comparing an electron-rich cavity and two finely adjustable rims, which has sparked considerable interest. Furthermore, the straightforward synthesis, uncomplicated functionalization, and remarkable properties of pillar[n]arene based on supramolecular interactions make it an excellent candidate for material construction, particularly in generating interpenetrating supramolecular polymers. Polymers resulting from supramolecular interactions involving pillar[n]arene find potential in various applications, including fluorescence sensors, substance adsorption and separation, catalysis, light-harvesting systems, artificial nanochannels, and drug delivery. In this context, we provide an overview of these recent frontier research fields in the use of pillar[n]arene-based supramolecular polymers, which serves as a source of inspiration for the creation of innovative functional polymer materials derived from pillar[n]arene derivatives.

A cavitand-based supramolecular artificial light-harvesting system with sequential energy transfer for photocatalysis

A novel artificial light-harvesting system, featuring sequential energy transfer processes, has been successfully constructed, which demonstrated white light emission through a precise adjustment of the donor-acceptor ratio. To better mimic natural photosynthesis, the system is employed as a nanoreactor for the photocatalysis of a cross-dehydrogenative coupling (CDC) reaction in aqueous solution.

Naphth[4]arene: Synthesis, Conformations, and Application in Color-Tunable Supramolecular Crystalline Assemblies

Although the chemistry of macrocyclic arenes has seen rapid development in recent years, the synthesis of new macrocyclic arenes from aromatic rings with no directing groups remains a challenge. In this work, a new macrocyclic arene, naphth[4]arene (NA[4]A), composed of four naphthalene rings bridged by methylene groups, was synthesized using macrocycle-to-macrocycle conversion. NA[4]A shows 1,3-alternate and 1,2-alternate conformations in the solid state, which can be selectively obtained. By supramolecular co-assembly of NA[4]A and 1,2,4,5-tetracyanobenzene (TCNB) in different concentrations and temperatures, two conformation-dependent crystalline luminescent co-assemblies 1,2-NTC and 1,3-NTC can be selectively prepared. Interestingly, the two charge-transfer crystalline assemblies containing NA[4]A with different conformations show bright yellow and green fluorescence, and also display high photoluminescence quantum yields (PLQYs) of 45 % and 43 %. Furthermore, they exhibit color-tunable two-photon excited upconversion emission.

Emissive Click Cages

This study reports the synthesis of cofacial organic cage molecules containing aggregation-induced emissive (AIE) luminogens (AIEgens) through four-fold Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reactions. The shorter AIEgen, tetraphenylethylene (TPE), afforded two orientational isomers (TPE-CC-1A and TPE-CC-1B). The longer AIEgen, tetrabiphenylethylene (TBPE), afforded a single isomer (TBPE-CC-2). The click reaction employed is irreversible, yet it yielded remarkable four-fold click products above 40 %. The phenyl rings around the ethylene core generate propeller-shaped chirality owing to their orientation, which influences the chirality of the resulting cages. The shorter cages are a mixture of PP/MM isomers, while the longer ones are a mixture of PM/MP isomers, as evidenced by their x-ray structures. The newly synthesized cage molecules are emissive even in dilute solutions (THF) and exhibit enhanced AIE upon the addition of water. The aggregated cage molecules in aqueous solution exhibit turn-off emission sensing of nitroaromatic explosives, with selectivity to picric acid in the 25-38 nanomolar detection range.

Bismacrocycle: Structures and Applications

In the past half-century, macrocycles with different structures and functions, have played a critical role in supramolecular chemistry. Two macrocyclic moieties can be linked to form bismacrocycle molecules. Compared with monomacrocycle, the unique structures of bismacrocycles led to their specific recognition and assembly properties, also a wide range of applications, including molecular recognition, supramolecular self-assembly, advanced optical material construction, etc. In this review, we focus on the structure of bismacrocycle and their applications. Our goal is to summarize and outline the possible future development directions of bismacrocycle research.

An L-arginine-functionalized pillar[5]arene-based supramolecular photosensitizer for synergistically enhanced cancer therapeutic effectiveness

An L-arginine-functionalized pillar[5]arene-based supramolecular photosensitizer LAP5⊃NBSPD was constructed by host-guest interactions, which could self-assemble into nano-micelles to achieve effective delivery and selective release of LAP5 and NBS in cancer cells. In vitro studies revealed that LAP5⊃NBSPD NPs exhibited excellent cancer cell membrane disruption and ROS generation properties, which provides a novel route for synergistically enhanced cancer therapeutic effectiveness.