Efficient Preparation of Functionalized Hybrid Organic/Inorganic Wells−Dawson-type Polyoxotungstates

Development of a chromatographic method for optimizing the thiol-maleimide coupling of polyoxometalate-polymer hybrids

The covalent attachment of polyoxometalates (POMs) to polymers has been developed as a strategic approach for the advancement of POM-based hybrid materials with versatile applications. In this study, we utilized thiol-maleimide Michael addition to investigate the kinetics and efficacy of the "one-to-one" conjugation between Keggin type POM and polystyrene. We explored the effects of solvent polarity, catalyst, molecular weight of PS and synthetic strategies on the reaction kinetics and efficiency, by means of reverse-phase high-performance liquid chromatography (RP-HPLC). A series of comparative analysis affirmed the superior efficiency of the one-pot method, particularly when facilitated by the addition of a high-polarity solvent and an excess of maleimide. These findings offer valuable insights into the intricate interplay between reaction conditions, kinetics, and selectivity in thiol-maleimide reactions of POMs and polymers. They hold profound implications for advancing the study of POM-based multifunctional materials and the synthesis of complex hybrid molecules.

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

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 In^III-substituted monodefect Wells-Dawson (WD) polyoxometalate (POM) cluster anions, [α₂-P₂W₁₇O₆₁In^IIIOH)]^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 In^III-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[P₂Cu^II(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.

Polyoxometalate-peptide hybrid materials: from structure-property relationships to applications

Organo-functionalisation of polyoxometalates (POMs) represents an effective approach to obtain diverse arrays of functional structures and materials, where the introduction of organic moieties into the POM molecules can dramatically change their surface chemistry, charge, polarity, and redox properties. The synergistic combination of POMs and peptides, which perform a myriad of essential roles within cellular biochemistry, including protection and transport in living organisms, leads to functional hybrid materials with unique properties. In this Perspective article, we present the principal synthetic routes to prepare and characterise POM-peptide hybrids, together with a comprehensive description of how their properties - such as redox chemistry, stereochemistry and supramolecular self-assembly - give rise to materials with relevant catalytic, adhesive, and biomedical applications. By presenting the state-of-the-art of the POM-peptide field, we show specifically how emerging chemical approaches can be harnessed to develop tailored POM-peptide materials with synergistic properties for applications in a variety of disciplines.

Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

Development of sterically hindered siloxide-functionalized polyoxotungstates for the complexation of 5d-metals

In this study, we extend the family of organosilyl-functionalized trivacant Keggin polyoxotungstates, [PW₉O₃₄(RSiOH)₃]^3- (R = ⁿPr, ⁱPr, ^tBu), through the introduction of bulky aryl and aliphatic silanol substituents, namely phenyl, cyclohexyl and biphenyl. This work was performed in order to study the impact of these large functional groups on the accessibility of the well-defined tridentate coordination site. Coordination of hafnium to these type II hybrid polyoxotungstates was conducted in order to study the ability of the bulkier ligand pockets to support larger cations in comparison to those previously reported (e.g. Ti⁴⁺, V³⁺, V⁵⁺, Ge⁴⁺). Increased steric hindrance around the coordination site from the biphenyl groups resulted in much longer reaction times for the complexation reaction compared to the other functional groups used, but the impact of our design toward stabilizing reactive species proved limited, as all complexes easily undergo hydrolysis of the Hf-O^tBu bond in the presence of water. Electrochemical investigations of the ligands and hafnium complexes reveal that the redox events centered on the polyoxotungstate core can be tuned by varying the substituents on the silyl fragment, and exhibit a cathodic shift after coordination of the redox inactive tetravalent cation.

Organic-Inorganic Two-Dimensional Hybrid Networks Constructed from Pyridine-4-Carboxylate-Decorated Organotin-Lanthanide Heterometallic Antimotungstates

Six organic-inorganic hybrid pyridine-4-carboxylate-decorated organotin (OT)-lanthanide (Ln) heterometallic antimotungstates [Ln(H₂O)₆(pca)]H[Sn(CH₃)₂(H₂O)]₃[B-β-SbW₉O₃₃]·12H₂O [Ln = La³⁺ (1), Ce³⁺ (2), Pr³⁺ (3), Nd³⁺ (4), Sm³⁺ (5), Eu³⁺ (6); Hpca = isonicotinic acid] have been prepared with the help of the structure-directing effect of the trivacant [B-α-SbW₉O₃₃]^9- segment toward [(CH₃)₂Sn]²⁺ and Ln³⁺ ions in an acidic water medium. The prominent architecture characteristic is that their structural units consist of a trivacant [B-β-SbW₉O₃₃]^9- segment stabilized by three [Sn(CH₃)₂(H₂O)]²⁺ groups and a [Ln(H₂O)₆(pca)]²⁺ cation, which are interconnected to propagate an intriguing two-dimensional (2D) network. For all we know, 1-6 stand for the first 2D OT-Ln heterometallic polyoxometalates. Furthermore, luminescence performances of solid-state 3-6 were deeply surveyed at ambient temperature. Energy migration from [B-β-SbW₉O₃₃]^9- and pca^- to Sm³⁺ centers in 5 was also studied. Comparative studies demonstrate that the contribution of [B-β-SbW₉O₃₃]^9- sensitizing the emission of Sm³⁺ is prominently larger than that of pca^- sensitizing the emission of Sm³⁺ in the emission process of 5. Most interestingly, 6 as a fluorescence probe exhibits high selectability and sensitivity for recognizing Zn²⁺ and Cu²⁺ in water.

A Bis-organosilyl-Functionalized Wells-Dawson Polyoxometalate as a Platform for Facile Amine Postfunctionalization

The development of modular platforms that can undergo postfunctionalization reactions permits coupling of inorganic clusters with different organic functionalities, thereby expanding the range of key physicochemical properties that are relevant for applications in different areas of science. In this work, a novel hybrid Wells-Dawson polyoxometalate (POM) platform was developed and successfully used for postfunctionalization via a nucleophilic substitution reaction. Two new halogen-functionalized bis-organosilyl Wells-Dawson POMs TBA₆[α₂-P₂W₁₇O₆₁{O(SiC₃H₆-X)₂}] (X = Cl or I) were synthesized, and their coupling with amine substrates was explored in a one-step postfunctionalization reaction. The iodide form of the POM has proven to be much more reactive, and its reaction with a range of primary and secondary amines resulted in a series of new bis-substituted Wells-Dawson POMs with the general formula TBA₆[α₂-P₂W₁₇O₆₁{O(SiC₃H₆-NR₁R₂)₂}]. Coupling of 18 amines with R₁ and R₂ groups, which exhibited a wide variety in terms of both chemical nature and bulkiness, was achieved under mild conditions via a catalyst-free approach. Using Na₂CO₃ as a base in acetonitrile solutions at 55 °C resulted in hybrid products that were obtained in high purity and good yields, after a simple isolation and purification procedure.

Hybrid polyoxometalates as post-functionalization platforms: from fundamentals to emerging applications

Polyoxometalates (POMs) represent an important group of metal-oxo nanoclusters, typically comprised of early transition metals in high oxidation states (mainly V, Mo and W). Many plenary POMs exhibit good pH, solvent, thermal and redox stability, which makes them attractive components for the design of covalently integrated hybrid organic-inorganic molecules, herein referred to as hybrid-POMs. Until now, thousands of organic hybrid-POMs have been reported; however, only a small fraction can be further functionalized using other organic molecules or metal cations. This emerging class of 'post-functionalizable' hybrid-POMs constitute a valuable modular platform that permits coupling of POM properties with different organic and metal cation functionalities, thereby expanding the key physicochemical properties that are relevant for application in (photo)catalysis, bioinorganic chemistry and materials science. The post-functionalizable hybrid-POM platforms offer an opportunity to covalently link multi-electron redox responsive POM cores with virtually any (bio)organic molecule or metal cation, generating a wide range of materials with tailored properties. Over the past few years, these materials have been showcased in the preparation of framework materials, functional surfaces, surfactants, homogeneous and heterogeneous catalysts and light harvesting materials, among others. This review article provides an overview on the state of the art in POM post-functionalization and highlights the key design and structural features that permit the discovery of new hybrid-POM platforms. In doing so, we aim to make the subject more comprehensible, both for chemists and for scientists with different materials science backgrounds interested in the applications of hybrid (POM) materials. The review article goes beyond the realms of polyoxometalate chemistry and encompasses emerging research domains such as reticular materials, surfactants, surface functionalization, light harvesting materials, non-linear optics, charge storing materials, and homogeneous acid-base catalysis among others.

Well-confined polyoxometalate-ionic liquid in silicic framework for environmentally friendly asymmetric di-hydroxylation of olefins

Chiral 1,2-diols with a high yield could be directly prepared from asymmetric di-hydroxylation of olefins via an eco-friendly and enduring catalyst, in which abundant "chiral pools" of polyoxometalate-ionic liquid were target-designed into the silicic framework (POM-ILS) and well stabilized in aqueous media.

Manipulation of Self-Assembled Nanostructure Dimensions in Molecular Janus Particles

The ability to manipulate self-assembly of molecular building blocks is the key to achieving precise "bottom-up" fabrications of desired nanostructures. Herein, we report a rational design, facile synthesis, and self-assembly of a series of molecular Janus particles (MJPs) constructed by chemically linking α-Keggin-type polyoxometalate (POM) nanoclusters with functionalized polyhedral oligomeric silsesquioxane (POSS) cages. Diverse nanostructures were obtained by tuning secondary interactions among the building blocks and solvents via three factors: solvent polarity, surface functionality of POSS derivatives, and molecular topology. Self-assembled morphologies of KPOM-BPOSS (B denotes isobutyl groups) were found dependent on solvent polarity. In acetonitrile/water mixtures with a high dielectric constant, colloidal nanoparticles with nanophase-separated internal lamellar structures quickly formed, which gradually turned into one-dimensional nanobelt crystals upon aging, while stacked crystalline lamellae were dominantly observed in less polar methanol/chloroform solutions. When the crystallizable BPOSS was replaced with noncrystallizable cyclohexyl-functionalized CPOSS, the resulting KPOM-CPOSS also formed colloidal spheres; however, it failed to further evolve into crystalline nanobelt structures. In less polar solvents, KPOM-CPOSS crystallized into isolated two-dimensional nanosheets, which were composed of two inner crystalline layers of Keggin POM covered by two monolayers of amorphous CPOSS. In contrast, self-assembly of KPOM-2BPOSS was dominated by crystallization of the BPOSS cages, which was hardly sensitive to solvent polarity. The BPOSS cages formed the crystalline inner bilayer, sandwiched by two outer layers of Keggin POM clusters. These results illustrate a rational strategy to purposely fabricate self-assembled nanostructures with diverse dimensionality from MJPs with controlled molecular composition and topology.

[Ni(OH)3W6O18(OCH2)3CCH2OH](4-): the first tris-functionalized Anderson-type heteropolytungstate

Na₂[TMA]₂[Ni(OH)₃W₆O₁₈(OCH₂)₃CCH₂OH]·9H₂O represents the first covalent tris-functionalized Anderson-type heteropolytungstate and was characterized by single-crystal X-ray diffraction, electrospray ionization mass spectrometry, TGA and IR spectroscopy.

Na₂[TMA]₂[Ni(OH)₃W₆O₁₈(OCH₂)₃CCH₂OH]·9H₂O represents the first covalent tris-functionalized Anderson-type heteropolytungstate and was characterized by single-crystal X-ray diffraction, electrospray ionization mass spectrometry, TGA and IR spectroscopy. Zeta potential measurements in solutions containing human serum albumin were performed to investigate electrostatic interactions with [Ni(OH)₃W₆O₁₈(OCH₂)₃CCH₂OH]^4–.

Synthesis and characterization of a series of novel polyoxometalate-supported carbonyl manganese derivatives

A series of novel heteropolytungstates-supported carbonyl manganese derivatives have been synthesized, which are the first examples of grafting [Mn(CO)₃]⁺ moieties and Mn²⁺ on the tungsto-antimonates/bismutates.

A new boat-like tungstoarsenate functionalized by carboxyethyltin and its catalytic properties

The boat-like carboxyethyltin tungstoarsenate derivative was applied for the first time for oxidation catalysis and photocatalysis as well as for mimicking enzyme catalysis.

Boronic acid and boronic ester containing polyoxometalates

Three organoboron functionalized polyoxometalates have been synthesized using Schiff base chemistry including a boronic acid, its methyl ester and its trimethylene glycol ester.

19-Tungstodiarsenate(III) Functionalized by Organoantimony(III) Groups: Tuning the Structure-Bioactivity Relationship

A family of three discrete organoantimony(III)-functionalized heteropolyanions-[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)](10-) (1), [{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)](8-) (2), and [{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2](14-) (3)-have been prepared by one-pot reactions of the 19-tungstodiarsenate(III) precursor [As(III)2W19O67(H2O)](14-) with 2-(Me2NCH2)C6H4SbCl2. The three novel polyanions crystallized as the hydrated mixed-alkali salts Cs3KNa6[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)]·43H2O (CsKNa-1), Rb2.5K5.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)]·18H2O·Me2NCH2C6H5 (RbK-2), and Rb2.5K11.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2]·52H2O (RbK-3), respectively. The number of incorporated {2-(Me2HN(+)CH2)C6H4Sb(III)} units could be tuned by careful control of the experimental parameters. Polyanions 1 and 2 possess a dimeric sandwich-type topology, whereas 3 features a trimeric, wheel-shaped structure, representing the largest organoantimony-containing polyanion. All three compounds were fully characterized in the solid state via single-crystal X-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis, and their aqueous solution stability was validated by ultraviolet-visible light (UV-vis) and multinuclear ((1)H, (13)C, and (183)W) nuclear magnetic resonance (NMR) spectroscopy. Effective inhibition against six different types of bacteria was observed for 1 and 2, and we could extract a structure-bioactivity relationship for these polyanions.

An open chain carboxyethyltin functionalized sandwich-type tungstophosphate based on a trivacant Dawson subunit: synthesis, characterization and properties

A Dawson sandwich-type polyoxometalate {C(NH2)3}12H4[αββα-{(Sn(C3H4O2))2Mn2(P2W15O56)2}]·22H2O (abbreviated as SnR-Mn-P2W15), functionalized by open chain carboxyethyltin groups, was first prepared in aqueous solution under conventional reaction conditions, and then structurally characterized by physicochemical and spectroscopic methods. Single crystal X-ray diffraction analysis revealed that two Mn(2+) cations and two [Sn(CH2CH2COO)](2+) groups are located in the internal and external positions in the so-called equatorial region of SnR-Mn-P2W15, respectively. Intriguingly, two exposed carboxyl groups act as stretching-arm brackets, which provide a favorable structure for potential further functionalization. The electrocatalytic activity of SnR-Mn-P2W15 towards the reduction of hydrogen peroxide and nitrite was studied. Additionally, its acid catalysis and oxidation catalysis activities in organic synthesis were investigated.

Organoantimony(III)-Containing Tungstoarsenates(III): From Controlled Assembly to Biological Activity

A family of three sandwich-type, phenylantimony(III)-containing tungstoarsenates(III), [(PhSb(III) ){Na(H2 O)}As(III) 2 W19 O67 (H2 O)](11-) (1), [(PhSb(III) )2 As(III) 2 W19 O67 (H2 O)](10-) (2), and [(PhSb(III) )3 (B-α-As(III) W9 O33 )2 ](12-) (3), have been synthesized by one-pot procedures and isolated as hydrated alkali metal salts, Cs3 K3.5 Na4.5 [(PhSb(III) ){Na(H2 O)}As(III) 2 W19 O67 (H2 O)]⋅41H2 O (CsKNa-1), Cs4.5 K5.5 [(PhSb(III) )2 As(III) 2 W19 O67 (H2 O)]⋅35H2 O (CsK-2), and Cs4.5 Na7.5 [(PhSb(III) )3 (B-α-As(III) W9 O33 )2 ]⋅42H2 O (CsNa-3). The number of incorporated {PhSb(III) } units could be selectively tuned from one to three by careful control of the reaction parameters. The three compounds were characterized in the solid state by single-crystal XRD, IR spectroscopy, and thermogravimetric analysis. The aqueous solution stability of sandwich polyanions 1-3 was also studied by multinuclear ((1) H, (13) C, (183) W) NMR spectroscopy. Effective inhibitory activity against six different kinds of bacteria was identified for all three polyanions, for which the activity increased with the number of incorporated {PhSb(III) } groups.

Polyoxometalate-Based Organic-Inorganic Hybrids as Antitumor Drugs

Polyoxometalates (POMs) have shown encouraging antitumor activity. However, their cytotoxicity in normal cells and unspecific interactions with biomolecules are two major obstacles that impede the practical applications of POMs in clinical cancer treatment. Derivatization of POMs with more biocompatible organic ligands is expected to cause a synergetic effect and achieve improved bioactivity and biospecificity. Herein, the synthesis of an amphiphilic organic-inorganic hybrid is reported by grafting a long-chain organoalkoxysilane lipid onto a POM. The amphiphilic POM hybrid could spontaneously assemble into the vesicles and exhibits enhanced antitumor activity for human colorectal cancer cell lines (HT29) compared to that of parent POMs. This detailed study reveals that the amphiphilic nature of POM hybrids enables the as-formed vesicles to easily bind to the cell membranes and then be uptaken by the cells, thus leading to a substantial increase in antitumor activity. Such prominent antitumor action is mostly accomplished via cell apoptosis, which ultimately results in cell death. Our finding demonstrates that novel POM hybrids-based drugs with increased bioactivity could be obtained by decorating POMs with selective organic ligands.

A covalent polyoxomolybdate-based hybrid with remarkable electron reservoir properties

A new polyoxomolybdate-based hybrid platform TBA4[PMo11O39{Sn(p-C6H4I)}] is reported. The presence of a post-functionalisable iodo-aryl moiety allows the grafting of a ferrocenyl moiety onto the POM. The electrochemical characterisation shows the effect of molybdenum on the electron reservoir properties of POM-based hybrids, which are further enhanced upon the addition of an acid.

Step-by-step strategy from achiral precursors to polyoxometalates-based chiral organic-inorganic hybrids

Using two types of triol ligands, several novel asymmetrically triol-functionalized Anderson organic hybrids have been efficiently synthesized in high purity and good yields via a convenient two-step esterification reaction. These organic-inorganic hybrids are chiral and can be spontaneously resolved with suitable solvents. Their molecular and crystal structures have been confirmed by single-crystal X-ray diffraction studies. Stable solid-state chirality of the corresponding enantiopure crystals has also been confirmed definitively by CD spectra. Interestingly, these organic-inorganic hybrids possess a layer-by-layer structure, forming solvent-accessible nanoscale chiral channels via a 1D infinite helical chain substructure. TGA measurements indicated that the species of the central heteroatoms significantly effects the stability of these compounds.

Dawson-type Polyoxometalate Covalently Linked to Naphthalene: Synthesis, Characterisation and Material Properties

A novel covalently linked organic–polyoxometalate (POM) hybrid compound [N(C4H9)4]6[α2-P2W17O61{P(O)C6H4C≡CC10H7}2] (NOD) was prepared by Sonogashira coupling reaction of 1-iodonaphthalene with (NBu4)6[α2-P2W17O61{P(O)C6H4C≡CH}2] (OD), and characterised by NMR, infrared spectroscopy, UV–vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The UV–vis and luminescence spectra of NOD showed delocalisation and electron transfer in the hybrid system. The redox potential of the polyanion could be tuned by grafting organic composites on it. NOD displayed interesting electrical conductivity behaviours, photovoltage response, and photocatalytic activity.

N-alkylation of organo-imido substituted polyoxometalates: an efficient and stoichiometric approach for the easy post-modification of polyoxometalates

A high-yield post-functionalization protocol developed here provides an easy inclusion of the desired organic groups on a POM's highly negative surface.

Accurate calculation of31P NMR chemical shifts in polyoxometalates

We search for an optimal DFT/basis set combination for computationally reproducing³¹P NMR chemical shifts in polyoxometalates.

Gold-nanoparticle-based multifunctional amyloid-β inhibitor against Alzheimer's disease

Targeting amyloid-β (Aβ)-induced complex neurotoxicity has received considerable attention in the therapeutic and preventive treatment of Alzheimer's disease (AD). The complex pathogenesis of AD suggests that it requires comprehensive treatment, and drugs with multiple functions against AD are more desirable. Herein, AuNPs@POMD-pep (AuNPs: gold nanoparticles, POMD: polyoxometalate with Wells-Dawson structure, pep: peptide) were designed as a novel multifunctional Aβ inhibitor. AuNPs@POMD-pep shows synergistic effects in inhibiting Aβ aggregation, dissociating Aβ fibrils and decreasing Aβ-mediated peroxidase activity and Aβ-induced cytotoxicity. By taking advantage of AuNPs as vehicles that can cross the blood-brain barrier (BBB), AuNPs@POMD-pep can cross the BBB and thus overcome the drawbacks of small-molecule anti-AD drugs. Thus, this work provides new insights into the design and synthesis of inorganic nanoparticles as multifunctional therapeutic agents for treatment of AD.

Intramolecular anion effect in polyoxometalate-based organocatalysts: reactivity enhancement and chirality transfer by a metal oxide-organic cation interaction

An α1 -Dawson polyanion bearing a lateral side chain with a 4-aminopyridine end group was synthesized. This organopolyoxometalate catalyzes the addition of indenyl allyl silanes to cinnamoyl fluorides. The polyanionic framework influences the organocatalyst activity and selectivity. A moderate but nonzero chirality transfer from the chiral inorganic framework to the organic substrate was observed.

One-pot transformation of cellobiose to formic acid and levulinic acid over ionic-liquid-based polyoxometalate hybrids

Currently, levulinic acid (LA) and formic acid (FA) are considered as important carbohydrates for the production of value-added chemicals. Their direct production from biomass will open up a new opportunity for the transformation of biomass resource to valuable chemicals. In this study, one-pot transformation of cellobiose into LA and FA was demonstrated, using a series of multiple-functional ionic liquid-based polyoxometalate (IL-POM) hybrids as catalytic materials. These IL-POMs not only markedly promoted the production of valuable chemicals including LA, FA and monosaccharides with high selectivities, but also provided great convenience of the recovery and the reuse of the catalytic materials in an environmentally friendly manner. Cellobiose conversion of 100%, LA selectivity of 46.3%, and FA selectivity of 26.1% were obtained at 423 K and 3 MPa for 3 h in presence of oxygen. A detailed catalytic mechanism for the one-pot transformation of cellobiose was also presented.

Exploring the utility of organo-polyoxometalate hybrids to inhibit SOX transcription factors

Background

SOX transcription factors constitute an attractive target class for intervention with small molecules as they play a prominent role in the field of regenerative biomedicine and cancer biology. However, rationally engineering specific inhibitors that interfere with transcription factor DNA interfaces continues to be a monumental challenge in the field of transcription factor chemical biology. Polyoxometalates (POMs) are inorganic compounds that were previously shown to target the high-mobility group (HMG) of SOX proteins at nanomolar concentrations. In continuation of this work, we carried out an assessment of the selectivity of a panel of newly synthesized organo-polyoxometalate hybrids in targeting different transcription factor families to enable the usage of polyoxometalates as specific SOX transcription factor drugs.

Results

The residual DNA-binding activities of 15 different transcription factors were measured after treatment with a panel of diverse polyoxometalates. Polyoxometalates belonging to the Dawson structural class were found to be more potent inhibitors than the Keggin class. Further, organically modified Dawson polyoxometalates were found to be the most potent in inhibiting transcription factor DNA binding activity. The size of the polyoxometalates and its derivitization were found to be the key determinants of their potency.

Conclusion

Polyoxometalates are highly potent, nanomolar range inhibitors of the DNA binding activity of the Sox-HMG family. However, binding assays involving a limited subset of structurally diverse polyoxometalates revealed a low selectivity profile against different transcription factor families. Further progress in achieving selectivity and deciphering structure-activity relationship of POMs require the identification of POM binding sites on transcription factors using elaborate approaches like X-ray crystallography and multidimensional NMR. In summary, our report reaffirms that transcription factors are challenging molecular architectures and that future polyoxometalate chemistry must consider further modification strategies, to address the substantial challenges involved in achieving target selectivity.

An unprecedented (3,4,24)-connected heteropolyoxozincate organic framework as heterogeneous crystalline Lewis acid catalyst for biodiesel production

A novel 3D hexadecanuclear heteropolyoxozincate organic framework, IFMC-200, has been successfully synthesized based on a late transition metal-oxygen cluster. IFMC-200 not only represents the first example of (3,4,24)-connected framework but also contains the first 24-connected single metal cluster in a crystal structure. It exhibits superior thermal stability, good water-stability, and even insensitivity to the existence of acid and base within a certain range of pH values. Furthermore, it performs as a heterogeneous crystalline Lewis acid catalyst with good activity for the conversion of long-chain fatty acids rather than short-chain ones, and high recycling efficiency for esterification reaction of fatty acids with alcohols to produce biodiesel.

A novel carboxyethyltin functionalized sandwich-type germanotungstate: synthesis, crystal structure, photosensitivity, and application in dye-sensitized solar cells

A novel sandwich-type germanotungstate [C(NH2)3]10[Mn2{Sn(CH2)2COOH}2(B-α-GeW9O34)2]·8H2O (1) represents the first single crystalline polyoxometalate (POM) functionalized by open chain carboxyethyltin, which was designed and synthesized in aqueous solution and applied to a dye-sensitized solar cell (DSSC) for the first time. Its photosensitivity was explored through a fluorescence spectrum (FL), surface photovoltage spectrum (SPV), electrochemical method, and solid diffuse spectrum. 1 displays the primary features of sensitizers in DSSCs, and the efficiency of the solar cell is 0.22%. Delightedly, when 1 was employed to assemble a cosensitized solar cell configuration by preparing a 1-doped TiO2 electrode and additionally adsorbing N719 dyes, a considerably improved efficiency was achieved through increasing spectral absorption and accelerating electron transport, which is 19.4% higher than that of single N719 sensitization. This result opens up a new way to position different dyes on a single TiO2 film for cosensitization.

Amphiphilic polyoxometalate-paired polymer coated Fe₃O₄: magnetically recyclable catalyst for epoxidation of bio-derived olefins with H₂O₂

An amphiphilic composite with magnetic Fe3O4 core and dodecylamine-modified polyoxometalate-paired poly(ionic liquid) shell was synthesized and characterized by (1)H NMR, thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectroscopy, X-ray diffraction (XRD), and digital microscopy. Catalytic tests for H2O2-based epoxidation of bioderived olefins, along with comparisons to various counterparts, demonstrate well that this newly designed catalyst exhibits high activity and selectivity, coupled with convenient magnetic recovery, and effective regeneration. The unique amphiphilic catalyst structure and the intramolecular charge transfer between amino groups and heteropolyanions are revealed to be responsible for the catalyst's excellent performances in epoxidation reactions.