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We herein describe the comprehensive investigation of the complexation behavior of a guanidinium-modified calix[5]arene pentaisohexyl ether (GC5A) with a variety of typical luminescent dyes. Fluorescein, eosin Y, rose bengal, tetraphenylporphine sulfonate and sulfonated aluminum phthalocyanine were employed as classical aggregation-induced quenching dyes. 2-( p -Toluidinyl)naphthalene-6-sulfonic acid and 1-anilinonaphthalene-8-sulfonic acid were selected as representatives of intramolecular charge-transfer dyes. Phosphated tetraphenylethylene was involved as the classical aggregation-induced emission dye. Sulfonated acedan representing one example of two-photon fluorescent probes, was also investigated. A ruthenium(II) complex with carboxylated bipyridyl ligands was included as a representative candidate of luminescent transition-metal complexes. We determined the association constants of the GC5A–dye complexes by fluorescence titration and discuss the complexation-induced photophysical changes. In addition, a comparison of the complexation behavior of GC5A with that of other macrocycles and potential applications according to the diverse photophysical responses are provided.

Several dynamic processes, including tautomerism and macrocyclic inversion, in 1H-NMR prochiral solvating agents (pro-CSAs) are investigated. Various features of pro-CSA, including modes of interaction for complex formation, stoichiometry, binding strength and temperature effects were compared for three representative pro-CSA molecules. Structural effects of conjugated tetrapyrrole pro-CSA on the mechanism of enantiomeric excess determination are also discussed. Detailed analysis of species (complexes) and dynamic processes occurring in solution and their 1H-NMR spectral manifestations at various temperatures is presented.

Functionalized O 6 -corona[3]arene[3]tetrazines were synthesized efficiently and conveniently by means of a macrocyclic condensation reaction between N -functionalized 3,6-dihydroxyphthalimides and 3,6-dichlorotetrazine under mild conditions in a one-pot reaction manner. The novel macrocycles exist as a mixture of rapidly interconvertible conformers in solution while in the solid state they adopt the conformation in which three phthalimide units are cis,trans -orientated. Acting as electron-deficient macrocyclic hosts, the synthesized O 6 -corona[3]arene[3]tetrazines self-regulated conformational structures to complex anions in the gas phase and in the solid state owing to the anion–π noncovalent interactions between anions and the tetrazine rings.

The molecular host cucurbit[7]uril forms an extremely stable inclusion complex with the dicationic ferrocene derivative bis(trimethylammoniomethyl)ferrocene in aqueous solution. The equilibrium association constant for this host-guest pair is 3 x 10¹⁵ M⁻¹ (Kd = 3 x 10⁻¹⁶ M), equivalent to that exhibited by the avidin-biotin pair. Although purely synthetic systems with larger association constants have been reported, the present one is unique because it does not rely on polyvalency. Instead, it achieves its extreme affinity by overcoming the compensatory enthalpy-entropy relationship usually observed in supramolecular complexes. Its disproportionately low entropic cost is traced to extensive host desolvation and to the rigidity of both the host and the guest.

Photodynamic therapy (PDT) as a safe, non-invasive modality for cancer therapy, in which the low oxygen and high glutathione in the tumor microenvironment reduces therapeutic efficiency. In order to overcome these problems, we prepared a supramolecular photosensitive system of O2-Cu/ZIF-8@ZIF-8@WP6–MB (OCZWM), which was loaded with oxygen to increase the oxygen concentration in the tumor microenvironment, and the Cu2+ in the system reacted with glutathione (GSH) to reduce the GSH concentration to generate Cu+. It is worth noting that the generated Cu+ can produce the Fenton reaction, thus realizing the combination therapy of PDT and chemodynamic therapy (CDT) to achieve the purpose of significantly improving the anti-cancer efficiency.

Chirality in confined nanospaces has brought some new insights into chirality transfer, amplification, and chiroptical properties. However, chirality switching, which is a common phenomenon in biological systems, has never been realized in confined environments. Herein, we report a type of hexagonal metallacages that shows good host–guest interactions with ethoxy pillar[5]arene and pillar[6]arene, as confirmed by single‐crystal X‐ray analysis. Importantly, when a chiral pillar[5]arene‐based molecular universal joint (MUJ) is used as the guest, the host–guest complexation would drive the alkyl ring of the MUJ flip from outside to inside the cavity of its pillar[5]arene unit, which enables the configuration change along with the chirality inversion of the MUJ. Moreover, the host–guest complexation facilitates the chirality transfer from guests to hosts, giving circularly polarized luminescence to the system. This study provides a unique metallacage‐pillararene recognition motif for the chirality switching of planar chiral pillararenes, which will promote the construction of host–guest systems with tunable chirality for advanced applications. Hexagonal perylene diimide‐based metallacages with spacious cavities for binding pillararenes were prepared. Employing a chiral pillar[5]arene‐based molecular universal joint as a guest, the complexation induced alkyl chain flipping within the pillar[5]arene unit, changing the configuration and the chirality of the system. this also triggered circularly polarized luminescence emission from the metallacages.

Owing to their appealing three-dimensional structures and tunable photophysical properties, emissive metallacages have been widely applied in recognition and sensing, adsorption and separation, catalysis, etc . Recently, the application of emissive metallacages in biomedical fields has emerged as a hot research topic, because multiple biological functionalities can be facilely integrated into metallacage-based platforms to deliver different functions. In this review, the applications of emissive metallacages in bio-imaging, delivery and cancer theranostics are systematically summarized. The dilemmas and challenges of metallacage-based biomedical materials are also raised at the end of this review. We hope this review would provide some guidance for the construction of novel emissive metallacages with biological functions, and further advance the development of emissive metallacages as biomedical materials.

Achieving light-induced manipulation of controlled self-assembly in nanosized structures is essential for developing artificially dynamic smart materials. Herein, we demonstrate an approach using a non-photoresponsive hydrogen-bonded (H-bonded) macrocycle to control the self-assembly and disassembly of nanostructures in response to light. The present system comprises a photoacid (merocyanine, 1-MEH), a pseudorotaxane formed by two H-bonded macrocycles, dipyridinyl acetylene, and zinc ions. The operation of such a system is examined according to the alternation of self-assembly through proton transfer, which is mediated by the photoacid upon exposure to visible light. The host–guest complexation between the macrocycle and bipyridium guests was investigated by NMR spectroscopy, and one of the guests with the highest affinity for the ring was selected for use as one of the components of the system, which forms the host–guest complex with the ring in a 2:1 stoichiometry. In solution, a dipyridine and the ring, having no interaction with each other, rapidly form a complex in the presence of 1-MEH when exposed to light and thermally relax back to the free ring without entrapped guests after 4 h. Furthermore, the addition of zinc ions to the solution above leads to the formation of a polypseudorotaxane with its morphology responsive to photoirradiation. This work exemplifies the light-controlled alteration of self-assembly in non-photoresponsive systems based on interactions between the guest and the H-bonded macrocycle in the presence of a photoacid.

In Gram-negative bacteria, lipopolysaccharides (LPSs, also known as endotoxin) can induce extensive immune responses that will enable victims to produce severe septic shock syndrome. Because of the high mortality of sepsis in the face of standard treatment, advance detoxification schemes are urgently needed in clinics. Herein, we described a supramolecular detoxification approach via direct host–guest complexation by a giant macrocycle. Cationic pentaphen[3]arene (CPP3) bearing multiple quaternary ammonium groups was screened as a candidate antidote. CPP3 exhibited robust binding affinity toward LPS with an association constant of (4.79 ± 0.29) × 108 M−1. Co-dosing with an equivalent amount of CPP3 has been demonstrated to decrease LPS-induced cytotoxicity on a cellular level through inhibiting ROS generation and proinflammatory cytokine expression. In vivo experiments have further proved that post-treatment by CPP3 could significantly improve the survival rate of LPS-poisoned mice from 0 to 100% over a period of 3 days, and inflammatory abnormalities and tissue damage were also alleviated.

Inclusion of a biological photosensitizer and prototype of β-carbolines, norharmane (NHM), into the cavity of cucurbit[7]uril (CB[7]) has been investigated for the first time, by using 1H NMR and UV–visible spectroscopy, and ab initio calculations. Protonated NHM forms a very stable host–guest complex with CB[7] in aqueous solution, with a binding constant of (9.0 ± 0.5) × 104 M−1. The encapsulation of NHM into CB[7] has driven the prototropic equilibrium of NHM to protonated NHM (NHMH+) at neutral pH. A pH titration for the host–guest complex revealed a moderate shift of the acid–base equilibrium in the ground-state (from 7.2 to 7.9), which may be caused by the low polarity microenvironment of the CB[7] cavity. The CB[7] provides a binding pocket for the hydrophobic molecule, and the polar, carbonyl-lined portals offering an anchoring site for the positive charge of the cationic species NHMH+.