Monomer and Dimer of Mono‐titanium(IV)‐Containing α‐Keggin Polyoxometalates: Synthesis, Molecular Structures, and pH‐Dependent Monomer–Dimer Interconversion in Solution

Matsuki, Yusuke; Mouri, Yuki; Sakai, Yoshitaka; Matsunaga, Satoshi; Nomiya, Kenji

doi:10.1002/ejic.201201290

Cited by 18 publications

(5 citation statements)

References 52 publications

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“…For example, the peak assigned to TBA 11 H 3 (SiPtW 11 O 40 ) 2 2+ in Figure c could equally well be assigned to TBA 11 (H 2 O)[(SiPtW 11 O 39 ) 2 OH], a protonated, hydrated self-condensation product of the SiPtW 11 O 40 H 5– ion. Self-condensation of this type is well-known in the solution chemistry of monosubstituted Keggin ion derivatives, yielding well-characterized species such as (PTiW 11 O 39 ) 2 OH 7– , (PTiW 11 O 39 ) 2 O 8– , (SiRuW 11 O 39 ) 2 O n ‑ , and (PFeW 11 O 39 ) 2 O 10‑ …”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–

et al. 2014

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Acidification of an aqueous solution of K8SiW11O39 and K2Pt(OH)6 to pH 4 followed by addition of excess tetramethylammonium (TMA) chloride yielded a solid mixture of TMA salts of H2SiPtW11O40(4-) (1) and SiW12O40(4-) (2). The former was separated from the latter by extraction into an aqueous solution and converted into tetra-n-butylammonium (TBA) and potassium salts TBA-1 and K-1. The α-H2SiPtW11O40(4-) was identified as a monosubstituted Keggin anion using elemental analysis, IR spectroscopy, X-ray crystallography, electrospray ionization mass spectrometry, (195)Pt NMR spectroscopy, (183)W NMR spectroscopy, and (183)W-(183)W 2D INADEQUATE NMR spectroscopy. Both TBA-1 and K-1 readily cocrystallized with their unsubstituted Keggin anion salts, TBA-2 and K-2, respectively, providing an explanation for the historical difficulty of isolating certain platinum-substituted heteropolyanions in pure form.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–

et al. 2014

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“…This exciting field has recently been exemplified for titanium oxide clusters as a model system for TiO 2 surfaces: the combination of Ti‐O molecular clusters with polyoxometalates has already been conceptually demonstrated, while the ramifications of these findings and new applications are waiting to be explored (Figure 8c). [ 98,101 ]…”

Section: Discussionmentioning

confidence: 99%

“…Reproduced with permission. [ 98 ] Copyright 2013, Wiley‐VCH. d) Schematic illustration of the POM‐modified 3D‐printed ABS (acrylonitrile butadiene styrene) copolymer substrates used for heavy metal removal by the cation binding sites of the lacunary [α‐PW 9 O 34 ] 9− (abbreviated here as {PW 9 }).…”

Section: Discussionmentioning

confidence: 99%

Polyoxometalates on Functional Substrates: Concepts, Synergies, and Future Perspectives

et al. 2020

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POMs were studied as heterogeneous acid catalysts and oxidation catalysts. However, this approach is often affected by low specific surface areas, leading to reduced reactivity. [10] Later studies, therefore, pioneered the immobilization of POMs on high surfacearea substrates including porous silica and other metal oxides, [10] as well as more advanced materials such as carbon nanostructures [11] and metal-organic frameworks (MOFs). [9] This strategy can enable maximized exposure of the individual POM molecules to the reaction environment, and in addition, allows for facile separation by filtration or centrifugation. [12] While early studies on POM immobilization used heterogeneous supports for mechanical stabilization and maximized surface-area, more recent studies have moved toward added properties introduced by the support. These include light-absorption and charge transport by semiconductors (TiO 2 , CdSe, etc.), electrical conductivity (by carbons, metals, conductive polymers) as well as specific POM binding sites, as introduced in MOFs and organofunctionalized supports. Many contemporary studies in this field share a common interest in exploring the synergism between POM and substrate to tune and optimize reactivity and stability of the composite. The concept has been theoretically and experimentally described several decades ago as the so-called "microenvironment effect" (electronic charge enhancement) where entrapment of POM species in a 3D matrix has been shown to induce huge improvement of their electrocatalytic activity. [13][14][15] However, to-date, the understanding of the fundamental processes which govern synergism of POM-substrate interactions is still in its infancy, as mole cular-level understanding of these complex processes by experiment or theory is far from trivial. This is due to the vast number of materials combinations, which are currently studied, and is further complicated by the often unknown chemical structures of the POM-substrate interface which make theoretical studies difficult. Also, in situ/operando studies of these materials are still challenging, and instrumentational approaches to address these issues are still being developed and not widely available. Most current experimental studies, therefore, focus on macroscopic reactivity, while providing less insight into the underlying causes of the processes observed.This Progress Report aims at raising awareness of the vast benefits of exploring this under-researched area to enable full use of POM-substrate interactions including charge and energy transfer, band-gap, and frontier orbital alignment as well as interface design for stability and reactivity. These fundamental concepts can affect both the thermodynamics as well as the kinetics of the chemical processes studied so that new reactivity can be tailored by understanding of the interactions between POM and substrate. Given the fast-paced progress in the synthesis, application, and characterization of this materials class, this Progress Report will serve as a focal point for ...

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“…To achieve this, we built upon our use of polyoxometalate (POM) cluster anions as ligands for soluble complexes of anatase-TiO 2 and α-Fe 2 O 3 (hematite) , NCs. In those complexes, Ti IV or Fe III ionscoordinated in a pentadentate “in-pocket” fashion by monovacant Keggin and Wells–Dawson (WD) anionsform hydrolytically stable μ-O linkages to metal atoms at the surfaces of the respective metal oxide NCs. , Importantly, POM-complexed Ti IV and Fe III ions form related oxo linkages in molecular μ-oxo-bridged dimers such as [{PW 11 O 39 Ti} 2 -μ-O] 8– and [{PW 11 O 39 Fe} 2 -μ-O] 10– . , By analogy, the presence of μ-OH linkages between early- and late-transition-metal cations in dimeric POM complexes such as [{PW 11 O 39 Zr} 2 (μ-OH) 2 ] 8– , , [{A-α-PW 9 O 34 } 2 Hf 3 (μ-OH) 3 ] 8– , [{A-α-SiW 9 O 33 } 2 (Fe 4 (OH) 6 )] 10– , and [{A-α-SiW 9 O 33 } 2 (Cu 5 (OH) 4 (H 2 O) 2 ] 10– and between main-group cations in [{α,α-Si 2 W 18 O 66 }(M 4 (μ-OH) 6 )], where M = Al and Ga, and [(KIn 2 (μ-OH) 2 ){(α,α-Si 2 W 18 O 66 ) 2 }(In 6 (μ-OH) 13 (H 2 O) 8 )] 17– , suggested that POM-complexed metal ions might form stable μ-OH linkages to metal hydroxide NCs.…”

Section: Introductionmentioning

confidence: 99%

Polyoxometalate-Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange

et al. 2022

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Metal hydroxides catalyze organic transformations and photochemical processes and serve as precursors for the oxide layers of functional multicomponent devices. However, no general methods are available for the preparation of stable water-soluble complexes of metal hydroxide nanocrystals (NCs) that might be more effective in catalysis and serve as versatile precursors for the reproducible fabrication of multicomponent devices. We now report that InIII-substituted monodefect Wells–Dawson (WD) polyoxometalate (POM) cluster anions, [α2-P2W17O61InIIIOH)]8–, serve as ligands for stable, water-soluble complexes, 1, of platelike, predominantly cubic-phase (dzhalindite) In(OH)3 NCs that after optimization contain ca. 10% InOOH. Images from cryogenic tranmsission electron microscopy reveal numerous WD ligands at the surfaces of platelike NCs, with average dimensions of 17 × 28 × 2 nm, each complexed by an average of ca. 450 InIII-substituted WD cluster anions and charge-balanced by 3600 Na+ countercations. Facilitated by the water solubility of 1, countercation exchange is used to stoichiometrically disperse ca. 1800 Cu2+ ions in an atomically homogeneous fashion around the surfaces of each NC core. The utility of this impregnation method is illustrated by using the ion-exchanged material as an electrocatalyst that reduces CO2 to CO 15 times faster per milligram of Cu than does K6Cu[P2CuII(H2O)W17O61] (control) alone. More generally, the findings point to POM complexation as a promising method for stabilizing and solubilizing reactive d-, p-, and f-block metal hydroxide NCs and for enabling their utilization as versatile components in the fabrication of functional multicomponent materials.

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Monomer and Dimer of Mono‐titanium(IV)‐Containing α‐Keggin Polyoxometalates: Synthesis, Molecular Structures, and pH‐Dependent Monomer–Dimer Interconversion in Solution

Cited by 18 publications

References 52 publications

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–

Polyoxometalates on Functional Substrates: Concepts, Synergies, and Future Perspectives

Polyoxometalate-Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange

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Monomer and Dimer of Mono‐titanium(IV)‐Containing α‐Keggin Polyoxometalates: Synthesis, Molecular Structures, and pH‐Dependent Monomer–Dimer Interconversion in Solution

Cited by 18 publications

References 52 publications

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H2SiPtW11O404–

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H2SiPtW11O404–

Polyoxometalates on Functional Substrates: Concepts, Synergies, and Future Perspectives

Polyoxometalate-Complexed Indium Hydroxide: Atomically Homogeneous Impregnation via Countercation Exchange

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Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–

Synthesis and Characterization of the Platinum-Substituted Keggin Anion α-H₂SiPtW₁₁O₄₀^4–