QXAFS study of CO and H adsorption on Pt in [PtAu(PPh)]-H[PMoO] solid.

The adsorption behaviors of H and CO molecules in crown-motif [PtAu(PPh)]-H[PMoO] (PtAu8-PMo12) solids were investigated by quick-scan X-ray absorption fine structure (QXAFS) measurements with a time resolution of 0.1 s. The electronic state of Pt in PtAu8-PMo12 was drastically changed by the adsorption of H and CO molecules because of the formation of Pt-H/Pt-CO interactions.

Heteroatom Effect on Site-Selective Oxygen-Sulfur Substitution Reactions of Keggin-Type Polyoxotungstates.

Sulfur, a group 16 element, can substitute the oxygen sites of metal oxides, potentially providing them with unique properties and enabling new applications. Polyoxometalates (POMs) are anionic metal oxide clusters with wide structural diversity owing to arbitrary selection of their constituting metal atoms. However, substitution of the oxygen sites of POMs with sulfur atoms has been rarely explored.

Electronic state modulation of Ag nanoclusters within a ring-shaped polyoxometalate.

Atomically precise Ag nanoclusters display distinctive properties that are dictated by their structures and electronic states. However, manipulating the electronic states of Ag nanoclusters is challenging owing to their inherent instability and susceptibility to undesired structural changes, decomposition, and aggregation. Recently, we reported the synthesis of a body-centered cubic {Ag} nanocluster encapsulated within a ring-shaped polyoxometalate (POM) [PWO] by reacting 16 Ag-containing [PWO] with Ag using ,-dimethylformamide (DMF) as a mild reducing agent.

Synthesis of polyoxothiometalates through site-selective post-editing sulfurization of polyoxometalates.

Polyoxometalates (POMs) function as platforms for synthesizing structurally well-defined inorganic molecules with diverse structures, metals, compositions, and arrangements. Although post-editing of the oxygen sites of POMs has great potential for development of unprecedented structures, electronic states, properties, and applications, facile methods for site-selective substitution of the oxygen sites with other atoms remain limited. Herein, we report a direct site-selective oxygen-sulfur substitution method that enables transforming POMs [XWO] (X = Si, Ge) to Keggin-type polyoxothiometalates (POTMs) [XWOS] using sulfurizing reagents in an organic solvent.

Synthesis of a Gold-Silver Alloy Nanocluster within a Ring-Shaped Polyoxometalate and Its Photocatalytic Property.

Alloying is an effective method for modulating metal nanoclusters to enrich their structural diversity and physicochemical properties. Recent investigations have demonstrated that polyoxometalates (POMs) can act as effective multidentate ligands for silver (Ag) nanoclusters to endow them with synergistic properties, reactivity, catalytic properties, and stability. However, the application of POMs as ligands has been confined predominantly to monometallic nanoclusters.

Self-assembled molecular hybrids comprising lacunary polyoxometalates and multidentate imidazole ligands.

Self-assembly coordination bonding facilitates the creation of diverse inorganic-organic molecular hybrids with distinct structures and properties. Recent advances in this field have been driven by the versatility of organic ligands and inorganic units. Lacunary polyoxometalates are a class of well-defined metal-oxide clusters with a customizable number of reactive sites and bond directions, which make them promising inorganic units for self-assembled molecular hybrids.

Small Copper Nanoclusters Synthesized through Solid-State Reduction inside a Ring-Shaped Polyoxometalate Nanoreactor.

Cu nanoclusters exhibit distinctive physicochemical properties and hold significant potential for multifaceted applications. Although Cu nanoclusters are synthesized by reacting Cu ions and reducing agents by covering their surfaces using organic protecting ligands or supporting them inside porous materials, the synthesis of surface-exposed Cu nanoclusters with a controlled number of Cu atoms remains challenging. This study presents a solid-state reduction method for the synthesis of Cu nanoclusters employing a ring-shaped polyoxometalate (POM) as a structurally defined and rigid molecular nanoreactor.

Ultra-stable and highly reactive colloidal gold nanoparticle catalysts protected using multi-dentate metal oxide nanoclusters.

Owing to their remarkable properties, gold nanoparticles are applied in diverse fields, including catalysis, electronics, energy conversion and sensors. However, for catalytic applications of colloidal gold nanoparticles, the trade-off between their reactivity and stability is a significant concern. Here we report a universal approach for preparing stable and reactive colloidal small (~3 nm) gold nanoparticles by using multi-dentate polyoxometalates as protecting agents in non-polar solvents.

Porphyrin-Polyoxotungstate Molecular Hybrid as a Highly Efficient, Durable, Visible-Light-Responsive Photocatalyst for Aerobic Oxidation Reactions.

Organic-polyoxometalate (POM) hybrids have recently attracted considerable interest because of their distinctive properties and wide-ranging applications. For the construction of organic-POM hybrids, porphyrins are promising building units owing to their optical properties and reactivity, including strong visible-light absorption and subsequent singlet-oxygen (O*) generation. However, the practical utilization of porphyrins as photocatalysts and photosensitizers is often hindered by their own degradation by O*.

Molecular hybrids of trivacant lacunary polyoxomolybdate and multidentate organic ligands.

Functional molecular inorganic-organic hybrids of lacunary polyoxometalates and organic ligands attract much attention for advanced material applications. However, the inherent instability of lacunary polyoxomolybdates hinders the synthesis of hybrids and their utilization. Herein, we present a viable approach for the synthesis of molecular hybrids of trivacant lacunary Keggin-type polyoxomolybdates and multidentate organic ligands including carboxylates and phosphonates, which is based on the use of a lacunary structure stabilized by removable pyridyl ligands as a starting material.

Surface-exposed silver nanoclusters inside molecular metal oxide cavities.

The surfaces of metal nanoclusters, including their interface with metal oxides, exhibit a high reactivity that is attractive for practical purposes. This high reactivity, however, has also hindered the synthesis of structurally well-defined hybrids of metal nanoclusters and metal oxides with exposed surfaces and/or interfaces. Here we report the sequential synthesis of structurally well-defined {Ag} nanoclusters in the cavity of ring-shaped molecular metal oxides known as polyoxometalates.

Ligand-Protecting Strategy for the Controlled Construction of Multinuclear Copper Cores within a Ring-Shaped Polyoxometalate.

The ring-shaped polyoxometalate (POM) [PWO] contains a large cavity and is an attractive inorganic multidentate ligand for accumulating metal cations. Until now, several multinuclear metal cores are constructed within the {PW} framework in aqueous solvents. However, it is still challenging to control the number and arrangement of introduced metal cations because of the numerous coordination sites inside the {PW} framework.

Variable control of the electronic states of a silver nanocluster protonation/deprotonation of polyoxometalate ligands.

The properties of metal nanoclusters depend on both their structures and electronic states. However, in contrast to the significant advances achieved in the synthesis of structurally well-defined metal nanoclusters, systematic control of their electronic states is still challenging. In particular, stimuli-responsive and reversible control of the electronic states of metal nanoclusters is attractive from the viewpoint of their practical applications.

Supported Anionic Gold Nanoparticle Catalysts Modified Using Highly Negatively Charged Multivacant Polyoxometalates.

Although supported anionic gold nanoparticle catalysts have been theoretically investigated for their efficacy in activating O in aerobic oxidation reactions, limited studies have been reported due to the difficulty of designing these catalysts. Herein, we developed a feasible method for preparing supported anionic gold nanoparticle catalysts using multivacant lacunary polyoxometalates with high negative charges. We confirmed the strong and robust electronic interaction between gold nanoparticles and multivacant lacunary polyoxometalates, and the electronic states of the supported gold nanoparticle catalysts can be sequentially modulated.

Nanostructured Manganese Oxides within a Ring-Shaped Polyoxometalate Exhibiting Unusual Oxidation Catalysis.

Nanosized manganese oxides have recently received considerable attention for their synthesis, structures, and potential applications. Although various synthetic methods have been developed, precise synthesis of novel nanostructured manganese oxides are still challenging. In this study, using a structurally defined nanosized cavity inside a ring-shaped polyoxometalate, we succeeded in synthesizing two types of discrete 18 and 20 nuclear nanostructured manganese oxides, Mn18 and Mn20, respectively.

A Molecular Hybrid of an Atomically Precise Silver Nanocluster and Polyoxometalates for H Cleavage into Protons and Electrons.

Atomically precise silver (Ag) nanoclusters are promising materials as catalysts, photocatalysts, and sensors because of their unique structures and mixed-valence states (Ag /Ag ). However, their low stability hinders the in-depth study of their intrinsic reactivity and catalytic property accompanying their redox processes. Herein, we demonstrate that a molecular hybrid of an atomically precise {Ag } nanocluster and polyoxometalates (POMs) can efficiently cleave H into protons and electrons.

An Ultrastable, Small {Ag } Nanocluster within a Triangular Hollow Polyoxometalate Framework.

Small Ag nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face-centered-cubic-type small {Ag } nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si W O ] .

Controlled Assembly Synthesis of Atomically Precise Ultrastable Silver Nanoclusters with Polyoxometalates.

Silver nanoclusters have attracted scientific interest due to their properties and applications. However, practical synthetic methods to access these materials are still limited mainly due to the low stability. Here, we report a controlled assembly strategy for fabricating atomically precise silver nanoclusters using polyoxometalates (POMs) as structure-directing as well as functionalizing units.

Ring-Shaped Polyoxometalates Possessing Multiple 3d Metal Cation Sites: [{M(OH)}{M(OH)}PWO(OCH)] (M = Mn, Co, Ni, Cu, Zn).

A ring-shaped polyoxometalate (POM), [PWO] (P8W48), formed by condensation of four hexavacant lacunary α-Dawson-type [α-PWO] units, is an attractive superlacunary compound possessing a large cavity (approximately 10 Å). Although the introduction of metal species into the cavity was attempted in aqueous media using the K/Li salt of P8W48, we encountered several challenges: excess metal species are required, and K and/or Li remain in the cavity. Therefore, controlling the number and arrangement of the introduced metal species proved difficult.

Hexavacant γ-Dawson-type phosphotungstates supporting an edge-sharing bis(square-pyramidal) {OM(μ-O)(μ-OAc)MO} core (M = Mn, Co, Ni, Cu, or Zn).

In aqueous media, the introduction of additional metal species into polyoxometalates (POMs) with multiple vacant sites, such as a hexavacant Dawson-type phosphotungstate, which is of interest for the synthesis of novel metal oxide clusters, is generally difficult because they easily undergo self-condensation and/or structural decomposition. In this study, we succeeded in developing a novel synthetic method to obtain metal-substituted γ-Dawson-type phosphotungstate monomers by introducing metal species into an organic solvent-soluble lacunary phosphotungstate, TBA4H10[α-P2W12O48] (I) (TBA = tetra-n-butylammonium), in organic media. The reaction of I, which possessed two types of vacant sites, i.