Cation Translocation around Single Polyoxometalate-Organic Hybrid Cluster Regulated by Electrostatic and Cation-π Interactions

Endowing Polycyclic Aromatic Hydrocarbons with Induced Supramolecular Chirality by Engineering Cation-π Interaction

The cation-π interaction is a crucial noncovalent binding force prevalent in many biological and chemical systems, however, are rarely reported in chiral supramolecular systems. Here, a supramolecular chiral system is reported, wherein cation-π interaction play significant roles. The interaction involves a chiral cationic palladium complex (R-Pd) co-assembling with 12 different polycyclic aromatic hydrocarbons (PAHs), resulting in the formation of supramolecular gels in mixed solvents. This co-assembly induces supramolecular chirality in the PAHs, with cation-π interaction identified as the primary driving force. The confirmation of this interaction is supported by high-resolution mass, 1H NMR, nuclear overhauser effect spectroscopy (NOESY), XRD and CD. Most importantly, with the synergy of hydrogen bonds, the cation-π interaction can be stabilized in a mixed solvent containing water, leading the co-assembly to form supramolecular gel, as well as enhanced chiral induction of PAHs. This discovery serves as a proof-of-principle example showing how the weak cation-π interaction could be a powerful guide in attaining induced chirality of PAHs.

Polyoxometalates for the catalytic reduction of nitrogen oxide and its derivatives: from novel structures to functional applications

Nitrogen oxide and its derivatives, including nitroaromatic hydrocarbons and various other nitro compounds, are commonly used in industrial applications such as synthesizing drugs, dyes, pesticides, and explosives. However, these compounds are also highly toxic to the environment. Their long-term accumulation can significantly affect air and water quality and disrupt ecosystems. Thus, efficiently converting these harmful compounds into more valuable products through catalytic processes is an urgent challenge in chemical catalysis. In this regard, polyoxometalates (POMs) have emerged as promising inorganic molecular catalysts for the reduction of nitrogen oxide and its derivatives. Their unique structure, excellent redox properties, and versatile catalytic abilities contribute to their effectiveness. This review provides an overview of recent advancements in the POM-catalyzed reduction of nitrogen oxide and its derivatives, focusing on reducing nitroaromatic hydrocarbons and nitrogen oxides. Additionally, we discuss the reaction mechanisms involved in the catalytic process, explore the potential of POMs' structural features for the rational design and optimization of catalytic performance, and highlight future directions for developing POM-based catalysts.

Chirality of sub-nanometer nanowires/nanobelts

Chirality is a widespread phenomenon in the fields of nature and chemicals, endowing compounds with distinctive chemical and biological characteristics. The conventional synthesis of chiral nanomaterials relies on the introduction of chiral ligands or additives and environmental factors such as solvents and mechanical forces. Sub-nanometer nanowires (SNWs) and sub-nanometer nanobelts (SNBs) are one-dimensional nanomaterials with high anisotropy, nearly 100% atomic exposure ratio and some other distinctive characteristics. In addition to traditional synthesis methods, the intrinsic chirality of SNWs/SNBs can also be achieved by several methods, such as the construction of asymmetric defects and counterion exchange. Chiral SNWs/SNBs have wide application prospects in chiral catalysis, chiral optical devices, chiral drug delivery, chiral liquid crystal materials, chiral sensors, and so on. In this work, we briefly introduce several examples of the origination, amplification, and transfer of the chirality in SNWs/SNBs. This review aims to deepen chirality researchers' understanding of the fundamental origins of intrinsic chirality in SNWs/SNBs and lays the foundation for expanding their potential applications.

Tuning the Chirality Evolution in Achiral Subnanometer Systems by Judicious Control of Molecule Interactions

Chirality evolution from molecule levels to the nanoscale in an achiral system is a fundamental issue that remains undiscovered. Here, we report the assembly of polyoxometalate (POM) clusters into chiral subnanostructures in achiral systems by programmable single-molecule interactions. Driven by the competing binding of Ca2+ and surface ligands, POM assemblies would twist into helical nanobelts, nanorings, and nanotubes with tunable helicity. Chiral molecules can be used to differentiate the formation energies of chiral isomers and immobilize the homochiral isomer, where strong circular dichroism (CD) signals are obtained in both solutions and films. Chiral helical nanobelts can be used as circularly polarized light (CPL) photodetectors due to their distinct chiroptic responsivity for right and left CPL. By the fine-tuning of interactions at single-molecule levels, the morphology and CD spectra of helical assemblies can be precisely controlled, providing an atomic precision model for investigation of the structure-chirality relationship and chirality manipulation at the nanoscale.

Self-Assembly of Polyoxometalate-Based Sub-1 nm Polyhedral Building Blocks into Rhombic Dodecahedral Superstructures

Self-assembly of subnanometer (sub-1 nm) scale polyhedral building blocks can yield some superstructures with novel and interesting morphology as well as potential functionalities. However, achieving the self-assembly of sub-1 nm polyhedral building blocks is still a great challenge. Herein, through encapsulating the titanium-substituted polyoxometalate (POM, K7 PTi2 W10 O40 ) with tetrabutylammonium cations (TBA+ ), we first synthesized a sub-1 nm rhombic dodecahedral building block by further tailoring the spatial distribution of TBA+ on the POM. Molecular dynamics (MD) simulations demonstrated the eight TBA+ cations interacted with the POM cluster and formed the sub-1 nm rhombic dodecahedron. As a result of anisotropy, the sub-1 nm building blocks have self-assembled into rhombic dodecahedral POM (RD-POM) assemblies at the microscale. Benefiting from the regular structure, Br- ions, and abundant active sites, the obtained RD-POM assemblies exhibit excellent catalytic performance in the cycloaddition of CO2 with epoxides without co-catalysts. This work provides a promising approach to tailor the symmetry and structure of sub-1 nm building blocks by tuning the spatial distribution of ligands, which may shed light on the fabrication of superstructures with novel properties by self-assembly.

Bacterial hyperpolarization modulated by polyoxometalates for solutions of antibiotic resistance

Developing strategies against the antibiotic resistance is a major global challenge for public health. Here, we report the synergy of the combination of Preyssler-type polyoxometalates (POMs) ([NaP5W30O110]14- or [AgP5W30O110]14-) and ribosome-targeting antibiotics for high antibacterial efficiency with low risk of antibiotic resistance. Due to their ultra-small sizes and active surface ligands, POM anions show strong affinity to bacterial cell membrane and impose hyperpolarization of the bacterial cells as well as the decrease of Mg2+ influx by blocking Mg2+ transporters, which finally lead to the structural perturbations of ribosomes and instability of bacterial structures. The bacterial growth can, therefore, be regulated by the presence of POMs: a fraction of Bacillus subtilis shifted to a 'dormant', slow-growing cellular state (an extended lag phase) upon the application of subinhibitory concentration of POMs. An approach to combat antibiotic resistant bacteria by applying POMs at their early growth phase followed by antibiotic exposure is validated, and its high efficiency for bacterial control is confirmed.

Insulin‐Sensitizing Activity of Sub‐Nanoscaled Polyalkoxyvanadate Clusters

Sub‐nanoscaled polyalkoxyvanadates (PAOVs) functionalized with various aliphatic acids are evaluated for their insulin‐sensitizing activity in lowering the blood glucose levels of diabetic mice in typical glucose tolerance tests. All the PAOVs can restore the blood glucose to normal levels after a single oral administration of PAOVs. Among them, the myristic acid‐modified PAOVs enable the response of insulin to the repeated glucose challenges, lasting for up to 13 h. The combined administration of PAOVs exerts better glucose control over insulin alone, while the capric acid‐ and myristic acid‐modified ones can enhance the responsiveness of insulin to glucose challenge and is comparable to a clinical‐used derivative of insulin. Interestingly, continuous glucose monitoring shows that myristic acid‐modified PAOV derivatives sensitize the responsiveness of insulin, almost matching with that of a healthy pancreas. These discoveries open up new opportunities for the application of PAOVs to promote glucose‐responsive and long‐lasting activity of insulin, which are expected to aid the accurate blood glucose control in insulin therapy while reducing the number of insulin administrations.

Beyond Charge Balance: Counter-Cations in Polyoxometalate Chemistry

Polyoxometalates (POMs) are molecular metal-oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self-assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered. This review provides an overview of fundamental POM-cation interactions in solution, the resulting solid-state compounds, and behavior and properties that emerge from these POM-cation interactions. We will explore how application-inspired research has exploited cation-controlled design to discover new POM materials, which in turn has led to the quest for fundamental understanding of POM-cation interactions.

A universal strategy for fabrication and morphology control of polyoxometalate-based metal–organic frameworks

Fabrication of POM@MOFs by utilizing the oxidization of POMs to metals and the effect of polyoxoanion charge on POM@MOF morphology.

Competition and Cooperation among Different Attractive Forces in Solutions of Inorganic-Organic Hybrids Containing Macroionic Clusters

Hybrids composed of nanoscale inorganic clusters and organic ligands are ideal models for understanding the different attractive forces during the self-assembly processes of complex macromolecules in solution. The counterion-mediated attraction induced by electrostatic interaction from the large, hydrophilic macroionic clusters can compete or cooperate with other types of attractive forces such as hydrophobic interactions, hydrogen bonding, π-π stacking, and cation-π interactions from the organic ligands, consequently determining the solution behaviors of the hybrid molecules including their self-assembly process and the final supramolecular structures. The incorporation of organic ligands also leads to interesting responsive behaviors to external stimuli. Through the manipulation of the hybrid composition, architecture, topology, and solution conditions (e.g., solvent polarity, pH, and temperature), versatile self-assembled morphologies can be achieved, providing new scientific opportunities and potential applications.

Stabilizing γ-Alkyltin-Oxo Keggin Ions by Borate Functionalization

We report a hierarchical self-assembly engineering of tin-oxo clusters from nanosized hydrophobic clusters to a single-layer film of assembled clusters. These clusters are derivatives of the previously reported Na-centered butyltin Keggin ions, but they are bicapped with butyltin and with borate ligands. The formulas γ-[( n-BuSn)₁₄(OCH₃)₁₀(OH)₃O₉(NaO₄)(HBO₃)₂] and γ-[( n-BuSn)₁₄(OCH₃)₁₀(OH)₃O₉(NaO₄)(PhBO₂)₂] were determined from single-crystal X-ray diffraction and bulk solution characterization including small-angle X-ray scattering, electrospray ionization mass spectrometry, and multinuclear and multidimensional NMR (¹¹⁹Sn, ¹³C, and ¹H). Solution characterization confirms that borate functionalization inhibits the solution-phase β-γ Keggin isomer interconversion that was recognized prior for uncapped butyltin clusters, and in this case, the γ isomer is favored. The assembly of the γ-NaSn₁₄BO₃ clusters into a homogeneous Langmuir-Blodgett monolayer is the first step toward creating nanopatterned films for microelectronic devices.

Three polyoxometalates-based organic–inorganic hybrids decorated with Cu–terpyridine complexes exhibiting dual functional electro-catalytic behaviors

Three new polyoxometalates-based organic–inorganic hybrids decorated with Cu–terpyridine complexes were prepared by using one-pot methods. Compounds 1–3 demonstrate discrepant dual functional electro-catalytic activities toward reduction of nitrite and oxidation of ascorbic acid.