Development of hydroxylated cucurbit[n]urils, their derivatives and potential applications

Polymeric self-assembled cucurbit[n]urils: Synthesis, structures and applications

The relative preference in adsorption among 19 common gas molecules, namely, C2H2, C2H4, C2H6, CH4, X2, HX (X = F, Cl, Br), CO2, CS2, CO, H2, H2O, H2S, N2, NO2, and NO within the cavity of cucurbit[6]uril (CB[6]) is investigated via density functional theory computations. Energies associated with the dissociation of gas@CB[6] producing CB[6] and gas molecules show the order of the efficacy to be encapsulated within CB[6], C2H2@CB[6] being the most viable system. However, the dissociation free energy change implies that CB[6] is most efficient in accommodating Cl2 followed by C2H2 among the considered gas molecules. In general, guest molecules having large surface contact with the host and/or high polarizability and/or having acidic hydrogen to make hydrogen bond with >C═O show larger propensity to be encapsulated within CB[6] cavitand. Functionalized CB[6] are better candidates for gas adsorption than CB[6]. However, the nature of functionalization needed to improve the adsorption ability varies with the ...

Selectivity in Gas Adsorption by Molecular Cucurbit[6]uril

Cyclodextrins (CDs) are naturally occurring macromolecules widely used as excipients on pharmaceutical formulations, evidencing a large spectrum of applications in the pharmaceutical industry. Their unique ability to act as molecular containers by entrapping a wide range of guest molecules in their internal cavity makes them a remarkable excipient to improve drug apparent solubility, stability, and bioavailability, and a valuable tool for the assembly of new drug delivery systems. These features are especially useful when it comes to chemotherapy, as most of the anticancer drugs present both low permeability and reduced water solubility. Therefore, guest-host inclusion complexes offer several potential advantages not only regarding the improvement of pharmaceutical formulations characteristics but also considering the reduction of drug toxic side effects. The combination of CDs with additional technologies and materials constitutes a potential strategy towards the development of advanced and multifunctional CD-based delivery systems. Paclitaxel, curcumin, camptothecin, doxorubicin, and cisplatin are among the most studied molecules with anticancer activities and have been successfully incorporated in such nanosystems. Exciting results using CDs and CD-based delivery systems have been obtained so far, paving the way towards the attainment of intelligent delivery systems to possibly address cancer therapeutics' unmet needs. In this review, a comprehensive exposition concerning in vivo-tested CD and CD-based delivery systems for anticancer therapy is undertaken. Additionally, the authors address the multivalent functionalities of CD-based delivery systems, namely the incorporation of active target ligands, stimuli-responsiveness components, surface functionalization, or further associations with other delivery systems, aiming at improved in vivo anticancer therapies. Graphical abstract.

Cyclodextrin-based delivery systems for in vivo-tested anticancer therapies

Since the first example of substituted cucurbit[n]urils (Q[n]), decamethylcucurbit[5]uril (Me10Q[5]), was reported in 1992, numerous substituted Q[n]s have been synthesized and studied. In this review article, we focus on the recognition properties of the substituted Q[n]s toward a variety of organic species as well as the coordination chemistry of substituted Q[n]s with different metal ions, including alkali/alkaline-earth metals, transition metals, and lanthanides. Applications of substituted Q[n]s, and the self-assembly processes affording mechanically interlocked molecules (MIMs) are also described. The main purpose of this review is to highlight important advances in the blossoming field of substituted Q[n]s, which will likely be of interest to researchers in supramolecular chemistry.

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Supramolecular chemistry of substituted cucurbit[n]urils

Cucurbit[n]urils (Q[n]s), a relatively new class of macrocyclic hosts with a rigid hydrophobic cavity and two identical carbonyl-fringed portals, have attracted much attention since the first member of the Q[n]-family, cucurbit[6]uril (Q[6]), was structurally identified in 1981 by Mock and co-workers. The interactions of the rigid cavities and negative portals of Q[n]s have resulted in the development of two almost mutually exclusive areas of study, namely Q[n]-based host–guest chemistry and Q[n]-based coordination chemistry. However, researches has revealed that Q[n]-based host–guest inclusion interactions may be influenced by metal ion coordination at the Q[n] portals, and in turn, coordination of metal ions at the Q[n] portals could be promoted by the formation of Q[n]-based inclusion host–guest complexes. Thus, this review provides an overview of related advances and achievements involving such a combination of Q[n]-based host–guest chemistry and Q[n]-based coordination chemistry, which could become an emerging branch, that is, Q[n]-based host–guest-metal ion chemistry. In particular, it could be useful in the treatment of wastewater, kinetic studies, drug delivery, the construction of novel supramolecular frameworks, metal-catalyzed reactions, recognition or response to metal cations, and so on.

Cucurbit[ n ]uril-based host–guest-metal ion chemistry: an emerging branch in cucurbit[ n ]uril chemistry

A one-pot strategy was employed to synthesize a series of water-soluble cucurbit[7]uril-anchored polyacrylic acids (Q[7]-anchored PAAs) with high yields in the presence of an ammonium persulfate salt as both an initiator and an oxidant. The effects of acrylic acid, Q[7] feed mass and APS concentration on the formation of polymer nanocapsules have been investigated. The Q[7]-anchored PAAs can be further esterified with 2-naphthol to yield water-insoluble derivatives, which are characteristic of the stationary phase for absorption of basic dyes, especially neutral red.

Sai Feng Xue

Papers

Cucurbit[ n ]uril-based host–guest-metal ion chemistry: an emerging branch in cucurbit[ n ]uril chemistry

Direct syntheses of cucurbit[7]uril-anchored polyacrylic acid microspheres and adsorption of basic dyes by the derivative

Coordination and supramolecular assemblies of meta-hexamethyl-substituted cucurbit[6]uril with alkali metal ions