Supramolecular Association between γ-Cyclodextrin and Preyssler-Type Polyoxotungstate

NMR spectroscopy to study cyclodextrin-based host-guest assemblies with polynuclear clusters

Natural cyclodextrin (CD) macrocycles are known to form diverse inclusion complexes with a wide variety of organic molecules, but recent work has revealed that inorganic clusters also form multicomponent supramolecular complexes and edifices. Such molecular assemblies exhibit a high degree of organization in solution governed by various chemical processes including molecular recognition, host-guest attraction, hydrophobic repulsion, or chaotropic effect. Nuclear magnetic resonance (NMR) spectroscopy is one of the most efficient and practical analytical techniques to characterize the nature, the strength and the mechanism of these interactions in solution. This review provides a brief overview on recent examples of the contribution of NMR to the characterization of hybrid systems in solution based on CD with polynuclear clusters, including polyoxometalates (POMs), metallic clusters and hydroborate clusters. The focus will be first on using 1H (and 13C) NMR of the host, i.e., CD, to identify the nature of the interactions and measure their strength. Then, 2D NMR methods will be illustrated by DOSY as a means of highlighting the clustering phenomena, and by NOESY/ROESY to evidence the spatial proximity and contact within the supramolecular assemblies. Finally, other NMR nuclei will be selected to probe the inorganic part as a guest molecule. Attention will be paid to classical host-guest complexes Cluster@CD, but also to hierarchical multi-scale, multi-component assemblies such as Cluster@CD@Cluster.

Large anion binding in water

Large water-soluble anions with chaotropic character display surprisingly strong supramolecular interactions in water, for example, with macrocyclic receptors, polymers, biomembranes, and other hydrophobic cavities and interfaces. The high affinity is traced back to a hitherto underestimated driving force, the chaotropic effect, which is orthogonal to the common hydrophobic effect. This review focuses on the binding of large anions with water-soluble macrocyclic hosts, including cyclodextrins, cucurbiturils, bambusurils, biotinurils, and other organic receptors. The high affinity of large anions to molecular receptors has been implemented in several lines of new applications, which are highlighted herein.

Water-soluble Self-assembled {Pd84 }Ac Polyoxopalladate Nano-wheel as a Supramolecular Host

Polyoxopalladates (POPs) are a class of self-assembling palladium-oxide clusters that span a variety of sizes, shapes and compositions. The largest of this family, {Pd₈₄ }^Ac , is constructed from 14 building units of {Pd₆ } and lined on the inner and outer torus by 28 acetate ligands. Due to its high water solubility, large hydrophobic cavity and distinct ¹ H NMR fingerprint {Pd₈₄ }^Ac is an ideal molecule for exploring supramolecular behaviour with small organic molecules in aqueous media. Molecular visualisation studies highlighted potential binding sites between {Pd₈₄ }^Ac and these species. Nuclear Magnetic Resonance (NMR) techniques, including ¹ H NMR, ¹ H Diffusion Ordered Spectroscopy (DOSY) and Nuclear Overhauser Spectroscopy (NOESY), were employed to study the supramolecular chemistry of this system. Here, we provide conclusive evidence that {Pd₈₄ }^Ac forms a 1 : 7 host-guest complex with benzyl viologen (BV²⁺ ) in aqueous solution.

Supramolecular Combination Cancer Therapy Based on Macrocyclic Supramolecular Materials

Supramolecular combination therapy adopts supramolecular materials to design intelligent drug delivery systems with different strategies for cancer treatments. Thereinto, macrocyclic supramolecular materials play a crucial role in encapsulating anticancer drugs to improve anticancer efficiency and decrease toxicity towards normal tissue by host-guest interaction. In general, chemotherapy is still common therapy for solid tumors in clinics. However, supramolecular combination therapy can overcome the limitations of the traditional single-drug chemotherapy in the laboratory findings. In this review, we summarized the combination chemotherapy, photothermal chemotherapy, and gene chemotherapy based on macrocyclic supramolecular materials. Finally, the application prospects in supramolecular combination therapy are discussed.

Infinite building blocks for directed self-assembly of a supramolecular polyoxometalate–cyclodextrin framework for multifunctional oxidative catalysis

With evolution from polyoxometalate-based molecular building blocks to infinite building blocks (IBBs), a supramolecular polyoxometalate–cyclodextrin framework was constructed by an IBB strategy for multifunctional oxidative catalysis.