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We first describe a photoinduced decatungstate-catalyzed direct coupling of cycloalkanes and cyclic aldimines. The desired products were generated in moderate to good yields with wide substrate scope under mild reaction conditions. The mechanistic study revealed a radical process. In addition, the usefulness of the reaction in organic synthesis was proved by the scale-up synthesis as well as the late-stage modification of drug-like molecules.

Here we report a mild protocol for benzylic C−H trifluoromethylthiolation using sodium decatungstate (NaDT) as the photocatalyst. Wherein, photoactivated DT abstracted the benzylic hydrogen atom via a radical process. This transformation works well with a slight excess of benzylic substrates or as limiting reagents for better purification. The reaction shows mild conditions and good functional group tolerance. Moreover, the protocol could be applied to gram‐scale synthesis. [ABSTRACT FROM AUTHOR]

In this study, we present an efficient and straightforward dearomative hydroalkylation of indoles. By utilizing alkanes or ethers as alkyl radical sources and employing TBADT as a cost‐effective photocatalyst for direct hydrogen atom transfers (HAT), we achieved successful conversion of these heterocyclic derivatives into 2‐alkylindolines with good to excellent yields and high diastereoselectivity under mild reaction conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] The alkylation of cyclic five-membered azomethine imines with carboxylic acids proceeds under irradiation with 400 nm light using a dual catalytic system consisting of 9-arylacridine and tetrabutylammonium decatungstate. Azomethine imines containing aromatic, heterocyclic and aliphatic groups are suitable for the process providing pyrazolidin-3-ones in 42–98% yields. [ABSTRACT FROM AUTHOR]

Herein we describe a sustainable and efficient photocatalytic method for the stereoselective radical alkylation of chiral sulfinyl imines. By employing readily available non‐prefunctionalized radical precursors and the cost‐effective TBADT as a direct HAT photocatalyst, we successfully obtain diverse chiral amines with high yields and excellent diastereoselectivity under mild conditions. This method provides an efficient approach for accessing a diverse array of medicinally relevant compounds, including both natural and synthetic α‐amino acids, aryl ethyl amines, and other structural motifs commonly found in approved pharmaceuticals and natural product. [ABSTRACT FROM AUTHOR]

We developed a site‐selective intermolecular C(sp3)−H alkylation of saccharides with electron‐deficient alkenes using photocatalysis by anthraquinone and tetrabutylammonium decatungstate (TBADT). The main reaction site of anthraquinone‐catalyzed C(sp3)−H alkylation is determined by the weakness of the C−H bond. The reaction site can be switched by changing the photocatalyst to TBADT, and the site‐selectivity is controlled by the steric hindrance between the bulkier TBADT photocatalyst and the substituents of the saccharides. The reaction is compatible with several electron‐deficient alkenes and saccharides, and provides C‐saccharides in good yields. Furthermore, the monoalkylated product was obtained in excellent yield, even on the gram scale, under TBADT photocatalysis. Applicability was demonstrated by site‐selective C(sp3)−H alkylation of glycosyl derivatives. The reactions proceed via a site‐selective hydrogen atom transfer between the photocatalyst and saccharide, and the generated carbon radical reacts with an electron‐deficient alkene to give alkylated products. [ABSTRACT FROM AUTHOR]

Although the functionalization and modification of single‐walled carbon nanotubes (SWCNTs) has been advanced for two decades, their chemical transformation via catalytic processes has yet to be explored and further facilitate their industrial utility. Here, the decatungstate‐photocatalyzed acylation is described of semiconducting (7,6)SWCNTs and the scope of the reaction is investigated by employing alkyl, aromatic, and organometallic aldehydes. The success of the methodology is confirmed by diverse spectroscopic, thermal, microscopy imaging, and redox techniques. The developed catalytic process for the functionalization of SWCNTs is environmetal friendly, since the catalyst and unreacted aldehydes can be recovered and reused, while the modified SWCNTs can be easily isolated and purified by membrane filtration. It is believed that the current findings will open new avenues for the catalytic functionalization of SWCNTs and the approach is intended to extend for modifying 2D nanomaterials. [ABSTRACT FROM AUTHOR]

Abstract Although the functionalization and modification of single‐walled carbon nanotubes (SWCNTs) has been advanced for two decades, their chemical transformation via catalytic processes has yet to be explored and further facilitate their industrial utility. Here, the decatungstate‐photocatalyzed acylation is described of semiconducting (7,6)SWCNTs and the scope of the reaction is investigated by employing alkyl, aromatic, and organometallic aldehydes. The success of the methodology is confirmed by diverse spectroscopic, thermal, microscopy imaging, and redox techniques. The developed catalytic process for the functionalization of SWCNTs is environmetal friendly, since the catalyst and unreacted aldehydes can be recovered and reused, while the modified SWCNTs can be easily isolated and purified by membrane filtration. It is believed that the current findings will open new avenues for the catalytic functionalization of SWCNTs and the approach is intended to extend for modifying 2D nanomaterials.

We report herein a convenient and scalable dearomative hydroacylation reaction of indoles. Employing readily available aldehydes as the acyl source and TBADT as an inexpensive direct HAT photocatalyst, a variety of indoles derivatives were converted into synthetically interesting 2‐acylindolines in good to excellent yields as well as great diastereoselectivity under mild conditions. An asymmetric version of the reaction was successfully developed and an experimental mechanistic investigation was carried out in order to gain further insights on the assumed reaction pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel catalysts were prepared based on surfactant-dispersed W-precursor. • Beneficial effects of the long-chain quaternary ammonium cation shell were confirmed. • The resulting supported catalysts had highly dispersed active phases with enhanced stacking. • Properties of W-precursors significantly affected the size and morphology of active phases. • The as-obtained catalysts exhibit superior activity for HDS of dibenzothiophene and HDN of quinoline compared with conventional catalysts. This article presents a surfactant-dispersed W precursor to prepare highly active hydrotreating (HDT) Al 2 O 3 -supported NiW catalyst. The proposed strategy converts polytungstate anions into surfactant-dispersed decatungstate precursor with a core–shell structure, which is then successfully deposited onto the pore channels of γ-alumina under moderate hydrothermal conditions. A variety of characterization methods, including X-ray diffraction (XRD), inductively coupled plasma-optical emission spectrometry (ICP-OES), N 2 adsorption–desorption, fourier transform infrared (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), Raman spectroscopy, and H 2 temperature programmed reduction (H 2 -TPR) were employed to identify the structure and composition of synthesized W precursor, as well as its states on the catalyst surface after drying and after calcination. After sulfidation, slab morphology and proportion of WS 2 and NiWS phases on the as-obtained sulfide catalysts were determined by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Results show that the hydrothermal deposition method ensures the the uniform distribution of the W species. Moreover, the long-chain quaternary ammonium cation shell of as-prepared W-precursor not only weakens the metal-support interaction, but also acts as a dispersant to prevent the aggregation of W species after decomposition. The multiple effects facilitate the formation of highly dispersed WS 2 slabs with enhanced stacking, and therefore yield a larger number of accessible NiWS edge sites after Ni incorporation. The resulted W/Al 2 O 3 and NiW/Al 2 O 3 catalysts exhibits higher HDT activity for dibenzothiophene (DBT) and quinoline (Q) removal in comparison with that of reference catalysts prepared from conventional precursor. The present work explores the essential role of surfactants in adjusting metal-support interaction and controlling the morphology of active phases, and reveals the directing effects of W-precursors on the size and morphology of active phases, thereby further shedding light on the rational design and controllable fabrication of supported WS 2 for efficient HDT. [ABSTRACT FROM AUTHOR]

Compound [Ag44(W10O32)(StBu)24(CF3COO)8](CF3COO)6 ⋅ 6H2O (1) was synthesized through a one‐pot method. This is the first case of isolating a new silver thiolate cluster containing a [W10O32]6− template which transforms from WO42− polyoxoanion through a self‐assembly process. The anionic nature of the reduced [W10O32]6− template and the effective silver‐oxygen interaction contribute to the formation of the Ag44 nanowheel in 1. The luminescence, photocatalytic activity and electrochemistry properties of 1 were studied. [ABSTRACT FROM AUTHOR]

The possibility of photocatalytic C(sp3)–H activation of aliphatic amines with the participation of decatungstate anion and their subsequent interaction with an acrylic acid ester has been demonstrated. Irradiation of reaction mixtures containing an aliphatic amine in the form of trifluoroacetic acid salt, acrylic acid tert-butyl ester, and sodium decatungstate Na4W10O32 or tetra-n-butylammonium has been shown to result in the formation of branched-chain amino acid esters. [ABSTRACT FROM AUTHOR]

This article reveals that molybdenum (Mo) heteroatoms isomorphously substituted decatungstates (Mo–DTs) can be conveniently synthesized via copolymerization of tungstate and molybdate in acidic solution. A series of characterizations support that the incorporated Mo heteroatoms play crucial roles in improving the redox capacity and visible light harvesting efficiency of Mo–DTs, especially the photo‐excited probability and lifetimes, so that the novel Mo–DTs exhibit a remarkably enhanced photo‐catalytic efficiency in the visible‐light‐triggered selective oxidation of inert hydrocarbons by O2 under mild conditions. In the photo‐oxidation of cyclohexane under continuous visible light irradiation for 30 h, the best 1 % Mo–DT can achieve 44.8 % conversion and 89.7 % cyclohexanone selectivity in the presence of 2 M HCl, and the regenerated catalyst after simple hydrothermal treatment has excellent reusability. This is the first successful example of incorporating Mo atoms into the skeleton of non‐lacunary DTs, which has special significance for expanding the application of DTs in visible‐light‐catalysis. [ABSTRACT FROM AUTHOR]

A novel decatungstate incorporated MOF of {[Cu(NPY)2(H2O)]2(W10O32)}·2DMF·3H2O (CuW–NPY; NPY = 3-amino-4,4′-bipyridine) has been synthesized by a diffusion method, and structurally characterized by elemental analyses, IR spectrum, UV–Vis spectrum, diffuse reflectance spectrum, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. CuW–NPY represents a novel decatungstate-based MOF with 1D quadrilateral channels (9.1 Å × 5.6 Å) constructed from Cu–NPY square grids and [W10O32]4− polyoxoanions via strong intermolecular hydrogen bonds and electrostatic interactions. Interestingly, CuW–NPY exhibits remarkable photocatalytic activities for the oxidation of cyclohexane to cyclohexanol and cyclohexanone with O2 under visible-light irradiation. The successful synthesis of CuW–NPY not only enriches decatungstate-based hybrid materials, but also represents the advantages of the decatungstate incorporated MOF for the selective oxygenation of organic compounds by O2. [ABSTRACT FROM AUTHOR]

A sunlight photocatalytic synthesis of aryl hydrazides was achieved via a decatungstate-promoted addition process of aromatic aldehydes to azo compounds. Aryl hydrazides can be produced in good to excellent yields under room temperature, even if the reaction was carried out as "window ledge" mode. This process is easy to be operated and no additional additives are needed, which makes the practicability and application value increase obviously. [ABSTRACT FROM AUTHOR]

Tetrabutylammonium decatungstate (TBADT) has emerged as a valuable photocatalyst for sunlight‐induced organic reactions. In this communication we wish to present its use for the photocatalytic oxidation of hydroxamic acids to generate fleeting nitrosocarbonyl intermediates. The reaction required a fine tuning of the conditions, especially in terms of solvent and additives, since an aqueous acetonitrile solution containing a mild base (NaHCO3) gave the best results. The obtained highly reactive nitrosocarbonyl species were then efficiently trapped with suitable dienes, such as cyclopentadiene and 1,3‐cyclohexadiene, to afford the corresponding Hetero Diels–Alder (HDA) cycloadducts in good yields. Dedicated photophysical experiments helped to elucidate the mechanistic scenario. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) are promising 2D nanomaterials for diverse applications, but their intrinsic chemical inertness hinders their modification. Herein, a novel approach is presented for the photocatalytic acylation of 2H-MoS 2 and 2H-MoSe 2 , utilizing tetrabutyl ammonium decatungstate ((nBu 4 N) 4 W 10 O 32 ) polyoxometalate complex as a catalyst and a conventional halogen lamp as a source of irradiation. By harnessing the semiconducting properties of TMDs, new avenues emerge for the functionalization of these materials. This novel photocatalytic protocol constitutes the first report on the chemical modification of 2D nanomaterials based on a catalytic protocol and applies to both aliphatic and aromatic substrates. The scope of the decatungstate-photocatalyzed acylation reaction of TMDs is explored by employing an alkyl and an aromatic aldehyde and the success of the methodology is confirmed by diverse spectroscopic, thermal, microscopy imaging, and redox techniques. This catalytic approach on modifying 2D nanomaterials introduces the principles of atom economy in a functionalization protocol for TMDs. It marks a transformative shift toward more sustainable and efficient methodologies in the realm of TMD modification and nanomaterial chemistry., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Using [(n-C4H9)4N]4[W10O32], AgNO3 and 4,4'-bipyridine (BPY) as raw materials, the first photosensitive H2 [Ag2 (W10O32) ( BPY)4] material was synthesized by hydrothermal method ( named AgW- BPY ), and its structure, optical properties and performance of heterogeneous photocatalytic oxidation of cyclo- hexane were studied. The results showed that the covalent bond between the photosensitivity [W10O32]4- polyacid anion and the MOF framework made [W10O32]4- polyacid anion difficult to dissolve from the MOF framework, and the heterogeneous immobilization of anions W10O324- poly acid was successfully realized; AgW-BPY had a band gap value of 2. 30 eV, which had the potential as a photocatalyst; under visible light irradiation at room temperature, AgW-BPY had good photocatalytic activity for molecular oxygen oxidize cyclohexane to cyclohexanone and cyclohexan, the conversion efficiency was 76. 1%,and the conversion rate was still 74. 5% after 3 cycles of experiments. [ABSTRACT FROM AUTHOR]

Abstract The reaction of [(n -C 4 H 9) 4 N] 4 [W 10 O 32 ], 3-amino-4,4′-bipyridine (NPY) and Cu(ClO 4) 2 ·6H 2 O by a diffusion method led to a novel 3D decatungstate-based MOF {[Cu(NPY) 2 (DMF)] 2 (W 10 O 32)}·DMF·3CH 3 CN (referred to as DT–NPY) with 1D hydrophilic/hydrophobic channels, which was structurally characterized by elemental analyses, IR spectrum, UV–Vis spectrum, powder X-ray diffraction (XRD) and single-crystal X-ray diffraction. DT–NPY exhibits remarkable photocatalytic activities for the oxidation of cyclohexane to cyclohexanone and cyclohexanol by molecular oxygen under mild conditions. The high catalytic efficiency, high stability and good recyclability of the photocatalyst DT–NPY demonstrates the superiority of the decatungstate imbedded MOF over homogeneous systems and other heterogenization methods. Graphical abstract A novel photosensitizing decatungstate-based MOF {[Cu(NPY) 2 (DMF)] 2 (W 10 O 32)}·DMF·3CH 3 CN has been prepared, which exhibits remarkable photocatalytic activities for the oxidation of cyclohexane to cyclohexanone and cyclohexanol by molecular oxygen. Unlabelled Image Highlights • a novel photosensitizing decatungstate-based MOF • the photocatalytic oxidation of cyclohexane with molecular oxygen • the high catalytic efficiency, high stability and good recyclability • the use of a free and renewable energy source as the light source [ABSTRACT FROM AUTHOR]

We investigated the removal of dibenzothiophene (DBT) and related compounds, 4-methyldibenzothiophene (4-MeDBT), 4,6-dimethyldibenzothiophene (4,6-DMeDBT), 2,8-dimethyldibenzothiophene (2,8-DMeDBT), and 1-benzothiophene (1-BT) from several oil media at room temperature under pressurized O 2 (0.6 MPa) by means of a three-phase reaction system consisting of the oil phase, an aqueous phase containing the phosphorus-free polyoxotungstate catalyst Na 4 W 10 O 32 ·8H 2 O, H 2 O 2 , and tetraoctylammonium bromide, and the gas phase. Under conditions in which the initial DBT concentration in octane was 10.1 mM, the desulfurization ratio reached 87% after reaction for 6.5 h. The sulfur atoms in the initial DBT were well accounted for by the sulfur atoms in the residual DBT, the dibenzothiophene sulfone and dibenzothiophene 5-oxide in the octane phase, and the dibenzothiophene sulfone that precipitated. Prolonged reaction time to 18 h resulted in 92% desulfurization. The desulfurization of octane decreased in the order 2,8-DMeDBT ~ DBT > 4-MeDBT >1-BT ~ 4,6-DMeDBT. Light oil and kerosene could also be desulfurized efficiently: after reaction for 6.5 h, the desulfurization ratios reached 77 and 78% for light oil and kerosene, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A mild and selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C−H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (−)‐ambroxide, pregnenolone acetate, (+)‐sclareolide, and artemisinin, exemplifies the utility of this new method. [ABSTRACT FROM AUTHOR]

In this work, porous decatungstate-TiO 2 composite thin film has been prepared by the electrodeposition method. The advantages of decatungstate as electrochromic material are discussed and the electrochromic performances of the composite film have also been systematically investigated. The transmittance decreased from 98.0% down to 50.8% at the wavelength of 550 nm under an applied potential of − 0.8 V. Good reversibility and reproducibility also can be observed in the composite electrochromic film. The porous structure of the composite film not only provides a large surface area for loading W 10 polyanions but is also beneficial for the fast diffusion of H + , which results in high electrochromic performances. [ABSTRACT FROM AUTHOR]

Synergistic control over the SH2 transition states of hydrogen abstraction exploiting polar and steric effects provides a promising cooperative strategy for site-selective C(sp3)−H functionalization using decatungstate anion photocatalysis. By using this photocatalytic approach, the C−H bonds of substituted lactones and cyclic ketones were functionalized selectively. In the remarkable case of 2-isoamyl 4-tert-butyl cyclohexanone ( 1 t) bearing five methyl, five methylene, and three methine C−H bonds, one methine C−H bond in the isoamyl tether was selectively functionalized. [ABSTRACT FROM AUTHOR]

A process for the selective oxidation of aromatic compounds into nitroso compounds based on a ternary system by simply mixing sodium decatungstate (NaDT)/Fe 3 O 4 /H 2 O 2 in an aqueous solution has been designed. NaDT and Fe 3 O 4 were well characterized via XRD, FTIR, TEM, XPS, etc. The catalytic selective oxidation performance of different systems (NaDT/Fe 3 O 4 /H 2 O 2 , NaDT/H 2 O 2 , etc.) was compared. The effects of different parameters (pH, H 2 O 2 , Fe 3 O 4 , and NaDT concentrations) are also investigated. In addition, this study is focused on the catalytic product analysis and catalytic mechanisms. The NaDT and Fe 3 O 4 were successfully synthesized and the interaction between Fe 3 O 4 and NaDT was found. Comparing the oxidation efficiency of sulfapyridine in the NaDT/H 2 O 2 binary system, the efficiency increases, in NaDT/Fe 3 O 4 /H 2 O 2 ternary system, by approximately 380 times. Nitroso-sulfapyridine (N-SPD) was shown to be the main product but hydroxy-sulfapyridine (SPD-OH) was produced, representing a maximum of 5 % SPD conversion, due to the presence of •OH radicals in the system. The oxidation efficiency and the selective conversion of sulfapyridine (SPD) to N-SPD reached up to 97 % and 81 %, respectively. The rate constant and the percentage of SPD disappearance reach a plateau when concentrations of NaDT, Fe 3 O 4 , and H 2 O 2 increase, with limit concentrations of approximately 40 µM, 0.8 g L−1, and 10.0 mM respectively. The obtained results demonstrated that the oxidation of SPD into N-SPD is efficient at pH lower than 5.0. The effectiveness of the system is based on a complex mechanism obtained through interactions between Fe 3 O 4 and NaDT, confirmed by the FTIR and XPS measurements, on one side and between NaDT and H 2 O 2 on the other side, as clearly demonstrated in cyclic voltammetry (CV). These interactions in the ternary system accelerate the redox cycle of NaDT and Fe 3 O 4 in the oxidation reaction, and facilitate the transfer of electrons from SPD to H 2 O 2 , contributing to the efficiency of SPD oxidation into N-SPD. [Display omitted] • Selective oxidation of sulfapyridine via NaDT/Fe 3 O 4 /H 2 O 2 system was demonstrated. • Efficient oxidation of sulfapyridine into nitroso-sulfapyridine, with high selectivity, is observed. • The interactions between NaDT and H 2 O 2 and between NaDT and Fe 3 O 4 are confirmed and proved. • High efficiency of this process is mainly due to the interactions between the components of catalytic process. [ABSTRACT FROM AUTHOR]

The photocatalytic performance of the g-C 3 N 4 photocatalyst was restricted by the low efficiency because of the fast charge recombination. The present work constructed a “killing two birds with one stone” composite (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 /g-C 3 N 4 heterostructured photocatalysts with the aim to greatly promote the charge separation and recycle decatungstate in aqueous solution. Decatungstate was immobilized on g-C 3 N 4 in the form of modified decatungstate (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 via surface bonding method for the first time. Furthermore, a novel ternary (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 /g-C 3 N 4 /rGO photocatalyst was successfully constructed by integrating graphene into the binary (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 /g-C 3 N 4 composite as the electron mediator. The photocatalysts were characterized by XRD, FTIR, FESEM, TEM, UV-vis DRS, PL and EIS measurement. The photocatalytic properties were evaluated in photodecomposition of aqueous methyl orange and phenol under visible-light irradiations. It has been shown that the obtained (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 /g-C 3 N 4 photocatalyst exhibited improved photocatalytic activity and enhanced reduced charge recombination as compared with those of g-C 3 N 4 and (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 . It has been found that the introduction of graphene revealed a synergistic effect between the (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 species, g-C 3 N 4 and graphene existed in the ternary photocatalyst. Consequently, the photocatalytic activity of the ternary (C 16 H 33 (CH 3 ) 3 N) 4 W 10 O 32 /g-C 3 N 4 /rGO photocatalyst was superior to that of the binary one, originating from its stronger visible-light absorption and more reduced charge combination. Finally, recycling experiments revealed that the ternary composite photocatalyst was not only highly efficient but also robust, because it can be used six times without loss of activity, which efficiently solved the problem of recycling decatungstate in reaction system. This work demonstrated that rational design and construction of g-C 3 N 4 -decatungstate composites could open up a new avenue for the development of new efficient visible-light photocatalysts for water disinfection. [ABSTRACT FROM AUTHOR]

Samples of uranium-containing liquid luminophores activated with Dy were prepared, and their properties were studied experimentally. Optical excitation of aqueous DyWO solutions leads to the transfer of the excitation energy from the decatungstate ligand to Dy, followed by sensitized luminescence of Dy. [ABSTRACT FROM AUTHOR]

The phase formation processes of isopolytungstates in the systemsCo2+––H+–DMF–H2O (DMF-dimethylformamide) with different acidities (Z = ν(H+)/ν = 1.14–1.60) have been studied. It was found that only cobalt(II) hepta-, para-, and decatungstates could be isolated from aqueous DMF solutions. The chemical and FTIR spectroscopic analysis of the products isolated from the system allowed determination of conditions of Co(II) decatungstate formation. Cobalt(II) decatungstate, [Co(C3H7NO)5]2[W10O32], was characterized by elemental and EDX spectral analysis, SEM, FTIR spectroscopy, thermal analysis, single-crystal X-ray diffraction, and by UV–vis spectroscopy analysis. [ABSTRACT FROM AUTHOR]

The development of mild and efficient process for the selective oxygenation of organic compounds by molecular oxygen (O 2 ) can be one of the key technologies for synthesizing oxygenates. Here, the photo-oxygenation of cyclohexane to cyclohexanol and cyclohexanone over tetrabutylammonium decatungstate (W 10 O 32 4− ) was carried out under visible light irradiation and pure O 2 atmosphere. The W 10 O 32 4− was found to be active to this photo-oxygenation in a pure acetonitrile (MeCN), which can achieve ca. 8.1% cyclohexane conversion with ca. 64.3% selectivity for cyclohexanone under sustained visible light irradiation of 12 h. Notably, the above-described photo-catalysis oxygenation was improved to some extent in the presence of some acidic additives such as10 M HCl, H 2 SO 4 , or H 3 PO 4 aqueous solution and benzenesulfonic acid, providing ca . 12.4–14.3% cyclohexane conversion with ca . 59.7–69.4% cyclohexanone selectivity. Moreover, this acid-promoted effect was further magnified in the case of adding a suitable amount of water, which can lead to enhancing conversion (16.8–20.0%) and improving cyclohexanone selectivity (68.2–78.3%). This acidic aqueous solution-promoted effect was also observed upon the W 10 O 32 4− -photocatalyzed oxygenation of other substrates like toluene, ethylbenzene and butanone. This is likely due to the acidic aqueous solutions playing important roles in improving photo-redox cycling of W 10 O 32 4− and preserving its stability, as supported by the UV–vis spectra and cyclic voltammetry measurements. [ABSTRACT FROM AUTHOR]

Decatungstate WO was efficiently intercalated between the layers of three-dimensionally ordered macroporous MgAl-layered double hydroxide. The structural and textural properties of as-prepared intercalated compound were characterized using different solid-state characterization techniques such as X-ray powder diffraction, FTIR and Raman spectroscopies and electronic microscopy. The photocatalytic properties of immobilized WO within MgAl structure were investigated using 2-(1-naphthyl) acetamide (NAD) as a model of pesticide. The influence of different parameters such as amount of catalyst, pH and oxygen concentration were investigated. An optimal NAD degradation was obtained for a photocatalyst concentration of 60 mg l. Under our experimental conditions, this heterogeneous photocatalyst induces photodegradation of 60 % of NAD after 17 h of irradiation at 365 nm and at pH 6.6. Interestingly, pesticide photodegradation leads to the mineralization of substrates to HO and CO and the photocatalyst can be recycled and reused without any loss of activity over four cycles. [ABSTRACT FROM AUTHOR]

Complementary techniques including laser flash photolysis have been used to investigate the mechanism of decatungstate photocatalyzed oxygenation of methanol in acetonitrile. A particular attention has been directed to determine the most important chemical and photophysical kinetic parameters of this peculiar reaction. Under continuous photolysis, kinetics of both oxygen consumption and hydrogen peroxide formation has been followed in a closed system. The reaction was stopped when a conversion of less than 10% in oxygen-saturated solutions was reached. Our work enlightens the following findings: (i) as expected on the basis of a hydrogen-atom-abstraction mechanism and relative CH bond dissociation energy, the reaction constant rate of reactive species wO with methanol is the weakest of all alcohols already studied, (ii) the methanol decatungstate photocatalyzed oxygenation in acetonitrile satisfies the photostationary state conditions only up to [CH3OH] ~ 2.5 M, (iii) the role of peroxyl radical is crucial since it not only leads to the resulting products, but it also oxidizes the reduced form of decatungstate H+W10O32 [ABSTRACT FROM AUTHOR]

By single crystal X-ray diffraction the crystal structure of the complex salt [Co(NH)Cl](WO)·4HO is determined and the IR spectrum is interpreted. The crystal chemical analysis of the structure of complex cations and decatungstate anions and their packing in the structure is performed. [ABSTRACT FROM AUTHOR]

Highlights: [•] (TiO2/W10O32) n films show high dyes removal ability due to synergistic catalysis. [•] Photocatalytic performance was found to be improved by the addition of H2O2. [•] Immobilization of catalyst on glass slides solves the recovery problem and significantly reduces the cost of treating wastewater. [Copyright &y& Elsevier]

A generalized synthesis method for decatungstate hybrids from bisulfate-based acidic ionic liquids was reported. N-butylpyridinium decatungstate [bPy]WO and 1-butyl-3-methylimidazolium decatungstate [bmIm]WO were synthesized and have been demonstrated to be good thermo-regulated phase transfer catalysts in an organic-solvent-free selective oxidation of alcohols under mild conditions. Advantages of heterogeneous and homogeneous catalysis are combined here, provided good self-separated and ease-of-recycling catalysts. Graphical Abstract: Decatungstates hybrids were synthesized in high yields directly from bisulfate-based ionic liquids, and used as novel catalysts in selective oxidation of alcohols to aldehydes or ketones. A homogeneous phase can be induced during reaction, and the catalyst could be self separated after reaction.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The degradation of the pesticide metsulfuron methyl was studied in aqueous solutions by using decatungstate anion, W10O32 4−, as a photocatalyst. An electron transfer process involving the highly oxidizing features of the decatungstate excited state, namely W10O32 4−*, was clearly observed. The degradation led to the oxidation of the pollutant and the formation of the decatungstate reduced species, i.e. W10O32 5−. In aerated as well as in oxygen-saturated solutions, the system was found to operate in a photocatalytic way with the formation of superoxide anion and the regeneration of the starting decatungstate species. The phototransformation of the pesticide metsulfuron methyl appeared to occur through three different reaction pathways involving the three main parts of the chemical structure: the aromatic ring, the sulfonylurea bridge and to a less extent the methoxy group of the triazine moiety. Under continuous excitation a partial mineralization of metsulfuron methyl was observed owing to the presence of the triazine structure. A mechanistic scheme for complete degradation of metsulfuron methyl is proposed. [Copyright &y& Elsevier]

Abstract: Four supported catalysts with the same tungsten loading were prepared by depositing decatungstate species W10O4− 32, through wet impregnation, on the surface of γ-alumina and silica at different pH values. The prepared samples were characterized using BET measurements as well as XRD, UV–vis DR, and XP spectroscopies. Higher dispersion of W(VI) oxo-species was obtained in the silica-supported catalysts compared with the corresponding alumina-supported ones. Within the same support, the dispersion was higher when the impregnation pH is lower than the point of zero charge (pzc) of the support. The decatungstate anions were present mainly on the silica surface without any modification, whereas these underwent a partial depolymerization on their deposition on the γ-alumina surface. The extent of depolymerization was less in the sample prepared at pH above pzc. These findings were explained in terms of the mode of deposition of the W(VI) species from the solution onto the support surface. The photocatalytic activity of the aforementioned catalysts, concerning the photooxidation of 1-phenylethanol, depends on the fraction of the W10O4− 32 supported species rather than on the W(VI) dispersion. Thus, extremely high conversions have been obtained over the silica-based catalysts and also over the γ-alumina-based catalyst prepared at relatively high pH. These catalysts also are very effective in the photooxidation of a series of secondary and primary benzyl alcohols, in which benzyl ketones and benzoic acids were formed as the only or major products, respectively. The easy separation of the solid catalyst from the reaction mixture, the high activity, selectivity, and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis. Based on product analysis and kinetic data on the heterogeneous oxidation of benzyl alcohols, we suggest that a hydrogen abstraction transfer (HAT) mechanism predominates with respect to an electron transfer (ET) one in these reactions. [Copyright &y& Elsevier]

Abstract: Alkylammonium decatungstates were covalently anchored to silica gel, furnishing efficient and robust heterogeneous catalysts able to activate H2O2 in the selective oxidation of sulfide to sulfoxide. The organic–inorganic hybrid materials were fully characterized, particularly by spectroscopic experiments. Primary propylammonium decatungstate was the most active catalyst. The use of low amounts of the heterogeneous catalyst (0.1 mol%) with a slight excess of 30% H2O2 (1.15 equiv.) in a nonchlorinated solvent (methanol) makes this oxidation reaction an environmentally benign chemical process. Leaching and recycling experiments revealed that the supported catalyst is not only highly efficient but also robust, because it can be used six times without loss of activity. Furthermore, the immobilized catalyst can tolerate different types of reaction solvents. Finally, this procedure was successfully applied to various sulfides, including allyl phenyl sulfide and dibenzyl sulfide. [Copyright &y& Elsevier]

Abstract: The application of heterogeneous catalysis to the oxidation of alkanes in mild conditions still remains a challenge although in the last decade many interesting approaches were proposed and examined delivering numerous significant results. Following our interest in C–H bond activation by photocatalysis with sodium decatungstate research on the possibility of its heterogenization on ion-exchange organic resins and a carbon material was undertaken. The photocatalytic activity of obtained heterogenized decatungstate for cyclohexane oxidation with molecular oxygen was examined. It was found that the highest activity was observed for decatungstate supported on an ion-exchange resin. The decatungstate concentration and loading effect on the reaction progress and selectivity was investigated. Catalyst loading on the support, contrary to catalyst concentration in the irradiated solution, determined the oxidation selectivity, i.e. the formation of cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide. The lower loading of decatungstate promoted cyclohexanone production whereas the catalysts of high decatungstate loading favoured cyclohexyl hydroperoxide generation. [Copyright &y& Elsevier]

Synthesis and crystal structure of an ionic compound consisting of decatungstate anion W10O324- and cupper coordination cations in the form of a cationic stacking column are reported. The effect of anions on the stacking pattern of the coordinating cations and crystal structure is discussed in combination with other compounds. Application of the compound to the photocatalytic decolorization of dye wastewater has also been tested and reported here. [ABSTRACT FROM AUTHOR]

The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity behavior has been evidenced by comparison with homogeneous oxidations. [ABSTRACT FROM AUTHOR]

Abstract: A combination of time-resolved techniques (part I) with kinetic isotope effects studies (part II) has been used to investigate the mechanism of the decatungstate (W10O32 4−) photocatalyzed oxidation of aromatic alcohols, in acetonitrile. It is demonstrated that aromatic alcohols exclusively react by hydrogen atom transfer (HAT) mechanism, like to that proposed for the analogous alkane oxidations, and not by an electron transfer (ET) which is predominant in alkenes. The primary and β-secondary isotope effects provide strong evidence for a stepwise mechanism, in which the hydrogen atom abstraction occurs in the rate-determining step of the reaction. The positive slope in Hammett kinetics suggests a radical intermediate for this reaction and supports an early transition state. [Copyright &y& Elsevier]

Abstract: Previous studies on the mechanism of decatungstate photocatalyzed reactions of aliphatic alcohols and of aromatic hydrocarbons in the presence of oxygen suggest that in the corresponding reactions of aryl alcohols, direct electron transfer can compete with hydrogen-atom transfer. A combination of steady-state (O2 consumption measurements under continuous photolysis) and of time-resolved (laser flash photolysis) techniques have been used to investigate the decatungstate photocatalyzed oxygenation of benzyl alcohol, 1-phenylethanol and 1-deuterium-1-phenylethanol. Based upon a series of observations (quantitative formation of peroxide, primary kinetic isotope effect) and the detailed examination of kinetic parameters derived from an extensive kinetic study, it is concluded that aromatic alcohols react by a hydrogen-atom transfer mechanism. [Copyright &y& Elsevier]

Abstract: It is shown that acetone may accompany acetonitrile and water in the very restricted category of conventional solvents for polyoxometalates and more specially decatungstate photocatalyzed reactions. The values of the lifetime, rate constant for inherent decay, and quantum yield for formation of the reactive wO transient in both solvents are practically identical. The only differences relate: (i) to the reactivity of acetone toward wO which is three to four times higher than that of acetonitrile, but remains relatively weak compared to the less reactive substrates, such as alkanes and (ii) to the fact that, in contrast to acetonitrile, no solvated ions have been detected in solutions of decatungstate in acetone by ESMS, thus excluding strong precomplexation. The relative values of the rate constants of reaction of wO with propan-2-ol in acetone, acetonitrile, and water are 1/1.8/23, respectively. This first solvent effect study is consistent with the oxyradical-like character of the reactive transient wO due to the presence of an electron-deficient oxygen center. [Copyright &y& Elsevier]

Abstract: The homogeneous decatungstate catalyzed photooxygenation of 1,1-diphenylethane and 9-methyl-9H-fluorene has been studied mechanistically. The primary and β-secondary kinetic isotope effects provide strong evidence for a stepwise mechanism, with a hydrogen atom abstraction in the rate-determining step. [Copyright &y& Elsevier]

Decatungstate (DT) is very potential photo-catalyst for the dioxygens (O 2)-based selective oxidation but still needs to be improved in photo-catalytic efficiency and regeneration. This paper discloses that Au nanoparticles (NPs)-loaded DT (Au/DT) is conveniently synthesized via the reduction of chloroauric acids introduced in the synthesis of DT. A series of characterizations and quenching tests support that the doped Au NPs can remarkably improve the visible-light- harvesting and photo-excited quantum efficiencies of DT, and as the excellent electronic transport carriers, they also plays an additional role in converting O 2 into the active superoxide (•O 2 -) anion radical. As a result, the suggested Au/DT exhibits a significantly enhanced photo-catalytic efficiency for the visible-light-triggered selective oxidation of inert hydrocarbons under 25–28 °C and 1 atm pure O 2 atmosphere. Under optimized conditions, the best 1%Au/DT achieves 64.2% conversion and 93% acetophenone selectivity in the photo-oxidation of ethylbenzene and it has an outstanding regeneration ability. The hybridizing engineering (HE) strategy of Au NPs doping can improve DT's visible light harvesting efficiency and redox capacity via lowering frontier orbital energy levels, and in which Au NPs as the excellent electronic transport carriers also hoist DT's photo-excited quantum efficiency and the reactivity of O 2 in the visible light-driven selective oxidation of inert hydrocarbons. [Display omitted] • Firstly realizing the doping of Au NPs in the cage of non-lacunary decatungstate (DT). • Doped Au NPs remarkably improve DT's photo-physiochemical and redox properties. • Doped Au NPs play a crucial role in converting O 2 into active •O 2 - anion radical. • Au/DT possesses significantly enhanced visible-light-catalytic performance. • Au/DT has a good application potential in photo-catalytic oxidation of hydrocarbons. [ABSTRACT FROM AUTHOR]

• Photocatalytic hydroxylation of benzene to phenol can be achieved by using O 2 as an oxidant. • The sodium decatungstate (W 10 O 32 4−) is an effective photocatalyst for the benzene hydroxylation reaction in an aqueous solution. • High phenol yield (17–41%) and selectivity (76–82%) can be obtained within 60 min under ambient conditions. • The addition of acetic acid as a co-solvent can significantly enhance phenol formation. A one-pot hydroxylation reaction, in which benzene is converted to phenol using oxygen under mild conditions has attracted attention as an environmentally benign alternative to the cumene method. Herein, we report on the photocatalytic hydroxylation of benzene to phenol with O 2 by using sodium decatungstate (W 10 O 32 4−) in air atmosphere (1 atm) and at low temperature (10 °C). W 10 O 32 4− was active for the benzene hydroxylation process in pure water, which achieved a ca. 16–23% phenol yield with a ca. 61–70% selectivity within 60 min. The phenol yield and the selectivity were improved through the addition of acetic acid to the reaction solution. This enhancement was due to the improved benzene solubility and suppressed benzene vaporization and phenol overoxidation. The effect of the reaction conditions on the phenol formation was investigated in detail. Under anaerobic conditions, the reduced form of W 10 O 32 4− was generated, with the simultaneous formation of phenol, whereas phenol was not formed in the reoxidation of the reduced decatungstate with O 2. According to a kinetic isotopic effect, the C−H bond activation process in benzene hydroxylation was dominated by electron transfer (KIE, k H / k D = 1.0). The reaction mechanism for hydroxylation of benzene to phenol was also discussed. [Display omitted] [ABSTRACT FROM AUTHOR]