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The optimization of multicomponent emissive layer (EML) deposition by slot-die coating for organic light-emitting diodes (OLEDs) is presented. In the investigated EMLs, the yellow-green iridium complex (Ir) was doped in two types of host: a commonly used mixture of poly(N-vinylcarbazole) (PVK) with oxadiazole derivative (PBD) or PVK with thermally activated delayed fluorescence-assisted dopant (10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-10H-spiro[acridine-9,9'-fluorene], SpiroAC-TRZ). In this article, OLEDs with EML prepared in air by slot-die coating, facilitating industrial manufacturing, are confronted with those with spin-coated EML in nitrogen. OLEDs based on PVK:PBD + 2 wt.% Ir-dopant exhibit comparable performance: ~13 cd A-1, regardless of the used method. The highest current efficiency (21 cd A-1) is shown by OLEDs based on spin-coated PVK with 25 wt.% SpiroAC-TRZ and 2 wt.% Ir-dopant. It is three times higher than the efficiency of OLEDs with slot-die-coated EML in air. The performance reduction, connected with the adverse oxygen effect on the energy transfer from TADF to emitter molecules, is minimized by the rapid EML annealing in a nitrogen atmosphere. This post-treatment causes more than a doubling of the OLED efficiency, from 7 cd A-1 to over 15 cd A-1. Such an approach may be easily implemented in other printing techniques and result in a yield enhancement. ispartof: POLYMERS vol:14 issue:16 ispartof: location:Switzerland status: published

Bimetallic nanoparticles (NPs) play a pivotal role in promoting high activity and selectivity towards various industrially important reactions in comparison to single metal NPs due to their modulated electronic and surface properties. Herein, we report the synthesis of non-precious CoCu NPs, which serve as an excellent catalyst for the selective oxidation of a wide range of electronically diverse benzyl alcohols to benzaldehydes, in the presence of tent-butyl hydroperoxide (TBHP) as an oxidant at room temperature. The excellent catalytic activity of CoCu NPs is ascribed to a two-fold synergistic effect arising from the combination of enhanced peroxide decomposition, active Co2+ catalyst regeneration driven by the faster redox processes (between Co3+ and Cu+), and a feasible cobalt dimerisation-regeneration process. The recoverability and reusability of CoCu NPs are also demonstrated. With the merits of low-cost and recyclable catalysis under mild conditions, the present catalyst represents an efficient and potential alternative to precious metal catalysts.

The oxidation of ferrous ions in acidic sulfate solutions at elevated air pressures was investigated. The effect of the Fe2+ concentration, initial H2SO4 concentration and partial oxygen pressure on the reaction rate were determined at three different temperatures, that is, T = 90, 70, and 50 degrees C. The effect on the reaction rate of the components that H2SO4 dissociates into, that is, HSO4-, H3O+, and SO42-, was established as well. A second order of reaction in Fe2+ and a first order of reaction in O-2 were determined. No clear order in either H2SO4 or the components H2SO4 dissociates into, could be established. For the.experiments with initial concentrations of H2SO4 of 1 M and higher the oxidation rate was not affected, that is, a zero order of reaction in H2SO4 for these concentrations. Therefore, the kinetic rate expression for the oxidation of Fe2+ at concentrations of H2SO4 of 1 M and higher can be calculated with R-Fe(2+) = d[Fe2+]/dt = k[Fe2+]P-2(O2), where the activation energy E-A was determined to be 60.3 kJ/mol.

Baeyer-Villiger monooxygenases (BVMOs) and evolved mutants have been shown to be excellent biocatalysts in many stereoselective Baeyer-Villiger transformations, but industrial applications are rare which is partly due to the insufficient thermostability of BVMOs under operating conditions. In the present study, the substrate scope of the recently discovered thermally stable BVMO, TmCHMO from Thermocrispum municipale, was studied. This revealed that the wild-type (WT) enzyme catalyzes the oxidation of a variety of structurally different ketones with notable activity and enantioselectivity, including the desymmetrization of 4-methylcyclohexanone (99% ee, S). In order to induce the reversal of enantioselectivity of this reaction as well as the transformations of other substrates, directed evolution based on iterative saturation mutagenesis (ISM) was applied, leading to (R)-selectivity (94% ee) without affecting the thermostability of the biocatalyst.

A dual mechanism for direct benzene catalytic hydroxylation is described. Experimental studies and DFT calculations have provided a mechanistic explanation for the acid-free, TpxCu-catalyzed hydroxylation of benzene with hydrogen peroxide (Tpx = hydrotrispyrazolylborate ligand). In contrast with other catalytic systems that promote this transformation through Fenton-like pathways, this system operates through a copper-oxyl intermediate that may interact with the arene ring following two different, competitive routes: (a) electrophilic aromatic substitution, with the copper-oxyl species acting as the formal electrophile, and (b) the so-called rebound mechanism, in which the hydrogen is abstracted by the Cu–O moiety prior to the C–O bond formation. Both pathways contribute to the global transformation albeit to different extents, the electrophilic substitution route seeming to be largely favoured., We thank MINECO for Grants CTQ2014-52769-C3-1-R and CTQ2014-54071-P and COST Action CARISMA CM1205. D. B. acknowledges the support from the Norwegian Research Council through the Centre of Excellence for Theoretical and Computational Chemistry (CTCC; grant No. 179568/V30), the Norwegian Metacenter for Computational Science (NOTUR; grant nn4654k) and the EU Research Executive Agency for a Marie Curie Fellowship (grant CompuWOC/618303). We also thank CATEDRA CEPSA-UHU for nancial support.

Oxidation of cyclohexane has been carried out using molecular oxygen over cobalt molybdenum oxide (CoMoO4) catalysts in solvent free conditions. The catalysts were prepared using citrate method with three different molar ratios of Co:Mo, 1:1, 1:2, and 2:1 along with individual oxides for comparative studies. While all the catalysts showed significant activity and selectivity, CoMoO4 with 1:1 ratio showed the best performance compared to the others with a conversion of 7.38%, with selectivity to cyclohexanol and cyclohexanone (KA oil) of 94.3%, in 1h. The performance of the catalyst, has been studied as a function of oxygen pressure, reaction temperature, and catalyst loading. It was observed that the catalyst deactivates during the course of the reaction. The reasons for deactivation and methods for restoring the activity have been studied. A kinetic model is presented that captures the complex kinetics and matches well with the experimental data. (c) 2016 American Institute of Chemical Engineers AIChE J, 62: 4384-4402, 2016

A mimic of the Wacker process for C=O bond formation in terminal olefins can be initiated by a combination of the Pd(II) and hypervalent iodine reagent, Dess-Martin periodinane to generate methyl ketones. This operationally simple and scalable method offers Markovnikov selectivity, has good functional group compatibility, and is mild and high yielding.

Alkyne C≡C bond breaking, outside of alkyne metathesis, remains an underdeveloped area in reaction discovery. Recently, nitrogenation has been reported to allow nitrile formation from alkynes. A new protocol for the metal-free C≡C bond cleavage of terminal alkynes to produce nitriles is reported. This method provides an opportunity to synthesize a vast range of nitriles containing aryl, heteroaryl, and natural product derivatives (38 examples). In addition, the potential of (t)BuONO to act as a powerful nitrogenating agent for terminal aryl alkynes is demonstrated.

Cellulose/silica hybrid material produced by a sol-gel method from cellulosic fibres and silica precursors (tetraethoxysilane and 3-aminopropyltriethoxysilane) was functionalized with alpha-[SiW9O37Ru3III(H2O)(x)Cl3-x]((10-x)-) (Ru-POM), and thoroughly characterised by C-13 and Si-29 solid state NMR, FTIR spectroscopy, UV-vis reflectance spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), and chemical analysis. The supported Ru-POM exhibited catalytic activity for the gas phase heterogeneous aerobic oxidation of formaldehyde (ca. 830 ppm in polluted air) at room temperature, in a packed-bed reactor operating at a linear velocity ca. 0.33 m/s and ca. 0.5 s residence time. Maximum formaldehyde uptake was 1.10 g/min per kg of hybrid material doped with Ru-POM (ca. 1.4% w/w). More than 400 turnovers were achieved without significant loss of catalytic activity and the only detected oxidation products of formaldehyde were carbon dioxide and water. A plausible mechanism for the catalytic oxidation of formaldehyde by supported Ru-POM has been proposed and includes formaldehyde oxidation in oxygenated ruthenium complex. (C) 2015 Elsevier B.V. All rights reserved.

The palladium-catalyzed oxidation of alkenes, the Wacker-Tsuji reaction, is undoubtedly a classic in organic synthesis and provides reliable access to methyl ketones from terminal alkenes under mild reaction conditions. Methods that switch the selectivity of the reaction to provide the aldehyde product are desirable because of the access they provide to a valuable functional group, however such methods are elusive. Herein we survey both the methods which have been developed recently in achieving such selectivity and discuss common features and mechanistic insight which offers promise in achieving the goal of a general method for anti-Markovnikov-selective olefin oxidations.

The palladium-catalyzed oxidation of alkenes, the Wacker-Tsuji reaction, is undoubtedly a classic in organic synthesis and provides reliable access to methyl ketones from terminal alkenes under mild reaction conditions. Methods that switch the selectivity of the reaction to provide the aldehyde product are desirable because of the access they provide to a valuable functional group, however such methods are elusive. Herein we survey both the methods which have been developed recently in achieving such selectivity and discuss common features and mechanistic insight which offers promise in achieving the goal of a general method for anti-Markovnikov-selective olefin oxidations.

The present work describes the application of scanning electrochemical microscopy (SECM) in the feedback mode to determine the kinetics of oxygen reduction at or near the liquid/liquid interface – between water and 1,2-dichloroethane (w/DCE). The system contained decamethylferrocene (DMFc) in DCE as the electron donor and acids in water as a proton source. In this approach, decamethylferrocenium (DMFc+) is reduced at the tip of a microelectrode in DCE and the electrogenerated DMFc reacts with protons and oxygen to be re-oxidized in a following chemical reaction (catalytic EC’ mechanism). When a high Galvani potential difference was applied across the liquid/liquid interface, protons would transfer rapidly to the organic phase. Under this condition, SECM approach curves towards the liquid/liquid interface showed dramatic current increases at distances far from the interface. This indicates that oxygen reduction takes place mainly in the bulk DCE; however, at lower Galvani potential differences, where the proton transfer is slow, oxygen reduction was also observed at the interface. Finally, SECM feedback mode measurements with the tip approaching a conductive substrate were used to determine the kinetics of the homogeneous reaction, with an obtained apparent rate constant of 0.2-0.5 m3 mol–1·s–1.

An efficient and environmentally benign method using Fe(III) sulfate as a terminal oxidant in the synthesis of methyl ketones from terminal olefins via the Wacker process is developed. The methodology offers high selectivity for a Markonikov product, shows good functional group compatibility, involves mild reaction conditions, and is operationally simple. Fe-2(SO4)(3) is the sole terminal oxidant in this process. The method holds potential for future applications in organic synthesis.

A copper-catalyzed method for synthesis of diaryl ketones (Ar-CO-Ar') through removal of benzylic -CH2-, -CO-, and -CHR- groups from Ar-CO-CXR-Ar' has been discovered. A number of symmetrical and unsymmetrical heterocyclic ketones, which are usually difficult to synthesize, can be prepared in good to excellent yields. This method was applied to the synthesis of the nonsteroidal anti-inflammatory drug suprofen (47 % yield over three steps). Based on preliminary mechanistic and kinetic studies, an active Cu/O2 species is proposed to mediate the rearrangement reaction. Carbon-carbon bonds constitute the basic foundation of synthetic chemistry. Protocols for the generation and cleavage of such bonds are indispensable for the synthesis of new organic scaffolds. Although carbon-carbon bond-formation techniques have been studied extensively, the cleavage of carbon-carbon bonds is still a difficult objective. The inert nature of the carbon-carbon bond makes its cleavage problematic, and gaining control of it is even more challeng

A mixed-ligand 3D metal-organic framework, [Ni(1,2-cpd)(bpe)(H2O)]n (1) [1,2-cpd = cis-cyclopentane-1,2-dicarboxylate, bpe = 1,2-di(4-pyridyl)ethylene], has been constructed. Topological analysis revealed that the structure is a 3-c uninodal 2D + 2D 3D polycatenated net with the Schlafli symbol 63. The compound is catalytically active towards the epoxidation reaction in heterogeneous media. It catalyses almost all types of olefinic substrates with equal efficiency. After reaction it can be recovered quite easily and can be used for further reaction without any loss of activity for several cycles. Variable-temperature magnetic susceptibility measurement reveals the presence of a weak antiferromagnetic interaction in compound 1.

A combination of therapies to treat cancer malignancies is at the forefront of research with the aim to reduce drug doses (ultimately side effects) and diminish the possibility of resistance emergence given the multitarget strategy. With this goal in mind, in the present study, we report the combination between the chemotherapeutic drug doxorubicin (DOXO) and the photosensitizing agent pheophorbide a (PhA) to inactivate HeLa cells. Photophysical studies revealed that DOXO can quench the excited states of PhA, detracting from its photosensitizing ability. DOXO can itself photosensitize the production of singlet oxygen; however, this is largely suppressed when bound to DNA. Photodynamic treatments of cells incubated with DOXO and PhA led to different outcomes depending on the concentrations and administration protocols, ranging from antagonistic to synergic for the same concentrations. Taken together, the results indicate that an appropriate combination of DOXO with PhA and red light may produce improved cytotoxicity with a smaller dose of the chemotherapeutic drug, as a result of the different subcellular localization, targets and mode of action of the two agents. ispartof: CANCERS vol:9 issue:2 ispartof: location:Switzerland status: published

In this work, Cu(II), Co(II) and Ni(II) complexes of the Schif base ((S, E)-2-(3,4-dimethoxybenzylideneamino)- 3-(1H-imidazol-4-yl) propionic acid) were synthesized and subsequently anchored onto amine functionalized silica. They were characterized by FT-IR, UV-vis., Si-29 NMR, TG-DTG, ESR, FE-SEM and AFM techniques, and employed as catalysts in cyclohexane oxidation using hydrogen peroxide oxidant. Silica supported Cu(II) catalyst was shown the highest catalytic activity (70%) than rest of the catalysts used. On the other hand, all the complexes were selective as they yield only cyclohexanol and cyclohexanone. Silica supported catalysts were maintained their catalytic activity over five successive catalytic run. As these catalysts are selective, reusable and functioning well with hydrogen peroxide, they could design the environment friendly catalytic system for effective cyclohexane oxidation.

The reaction of flavoenzymes with oxygen remains a fascinating area of research because of its relevance for reactive oxygen species (ROS) generation. Several exciting recent studies provide consistent mechanistic clues about the specific functional and structural properties of the oxidase and monooxygenase flavoenzymatic systems. Specifically, the spatial arrangement of the reacting oxygen that is in direct contact with the flavin group is emerging as a crucial factor that differentiates between oxidase and monooxygenase enzymes. A challenge for the future will be to use these emerging concepts to rationally engineer flavoenzymes, paving the way to new research avenues with far-reaching implications for oxidative biocatalysis and metabolic engineering.

The reaction of flavoenzymes with oxygen remains a fascinating area of research because of its relevance for reactive oxygen species (ROS) generation. Several exciting recent studies provide consistent mechanistic clues about the specific functional and structural properties of the oxidase and monooxygenase flavoenzymatic systems. Specifically, the spatial arrangement of the reacting oxygen that is in direct contact with the flavin group is emerging as a crucial factor that differentiates between oxidase and monooxygenase enzymes. A challenge for the future will be to use these emerging concepts to rationally engineer flavoenzymes, paving the way to new research avenues with far-reaching implications for oxidative biocatalysis and metabolic engineering.

Prediction of oxidative drug metabolism at the early stages of drug discovery and development requires fast and accurate analytical techniques to mimic the in vivo oxidation reactions by cytochrome P450s (CYP). Direct electrochemical oxidation combined with mass spectrometry, although limited to the oxidation reactions initiated by charge transfer, has shown promise in the mimicry of certain CYP-mediated metabolic reactions. The electrochemical approach may further be utilized in an automated manner in microfluidics devices facilitating fast screening of oxidative drug metabolism. A wide range of in vivo oxidation reactions, particularly those initiated by hydrogen atom transfer, can be imitated through the electrochemically-assisted Fenton reaction. This reaction is based on O-O bond activation in hydrogen peroxide and oxidation by hydroxyl radicals, wherein electrochemistry is used for the reduction of molecular oxygen to hydrogen peroxide, as well as the reduction of Fe(3+) to Fe(2+). Metalloporphyrins, as surrogates for the prosthetic group in CYP, utilizing metallo-oxo reactive species, can also be used in combination with electrochemistry. Electrochemical reduction of metalloporphyrins in solution or immobilized on the electrode surface activates molecular oxygen in a manner analogous to the catalytical cycle of CYP and different metalloporphyrins can mimic selective oxidation reactions. Chemoselective, stereoselective, and regioselective oxidation reactions may be mimicked using electrodes that have been modified with immobilized enzymes, especially CYP itself. This review summarizes the recent attempts in utilizing electrochemistry as a versatile analytical and preparative technique in the mimicry of oxidative drug metabolism by CYP.

Prediction of oxidative drug metabolism at the early stages of drug discovery and development requires fast and accurate analytical techniques to mimic the in vivo oxidation reactions by cytochrome P450s (CYP). Direct electrochemical oxidation combined with mass spectrometry, although limited to the oxidation reactions initiated by charge transfer, has shown promise in the mimicry of certain CYP-mediated metabolic reactions. The electrochemical approach may further be utilized in an automated manner in microfluidics devices facilitating fast screening of oxidative drug metabolism. A wide range of in vivo oxidation reactions, particularly those initiated by hydrogen atom transfer, can be imitated through the electrochemically-assisted Fenton reaction. This reaction is based on O-O bond activation in hydrogen peroxide and oxidation by hydroxyl radicals, wherein electrochemistry is used for the reduction of molecular oxygen to hydrogen peroxide, as well as the reduction of Fe(3+) to Fe(2+). Metalloporphyrins, as surrogates for the prosthetic group in CYP, utilizing metallo-oxo reactive species, can also be used in combination with electrochemistry. Electrochemical reduction of metalloporphyrins in solution or immobilized on the electrode surface activates molecular oxygen in a manner analogous to the catalytical cycle of CYP and different metalloporphyrins can mimic selective oxidation reactions. Chemoselective, stereoselective, and regioselective oxidation reactions may be mimicked using electrodes that have been modified with immobilized enzymes, especially CYP itself. This review summarizes the recent attempts in utilizing electrochemistry as a versatile analytical and preparative technique in the mimicry of oxidative drug metabolism by CYP.

Antioxidant enzymes such as superoxide dismutase (SOD) play a key role in the removal of reactive oxygen species produced during visible and ultraviolet irradiance stress in microalgae and plants. However, little is known about the enzymatic antioxidative stress responses in ecologically important Antarctic marine microalgae. SOD in particular is difficult to analyze, possibly due to problems in obtaining sufficient quantities necessary for reliable and reproducible enzymatic assays. The aim of the present work was to create a sensitive, easy-to-use and reliable method for SOD determination in Antarctic microalgal material by comparing and optimizing existing protein extraction procedures and SOD assays in the marine Antarctic diatom Chaetoceros brevis. Optimization was achieved in cell disruption (sonication) and protein extraction procedures, extraction buffers, SOD assay methods (xanthine/xanthine oxidase and NBT/ riboflavin photometric quantitative methods and native gel electrophoresis qualitative method) and the assay temperature. Protein extraction was optimal at low sonication amplitudes after a few pulses, irrespective of the type of buffer used. Extraction efficiency varied highly between the tested buffers; most protein was extracted in the presence of 1% of Triton X-100. SOD activity was best quantified using the NBT/riboflavin method in combination with a buffer containing potassium phosphate and Triton X-100. Moreover, the NBT/ riboflavin method was demonstrated to be the most reliable and sensitive method at low temperatures (5 degrees C). (c) 2007 Elsevier B.V. All rights reserved.

A chemoselective osmium(VI) catalyzed oxidation of benzylic, allylic and propargylic alcohols using K3Fe(CN)(6) as a secondary oxidant is described. This protocol is operationally simple and exhibits excellent chemoselectivity favouring the oxidation of benzylic alcohols over the aliphatic alcohols. A larger scale reaction was also found to be compatible.

New rhenium(VII or III) complexes [ReO3(PTA)2][ReO4] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), [ReO3(mPTA)][ReO4]I (2) (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane cation), [ReO3(HMT)2][ReO4] (3) (HMT = hexamethylenetetramine), [ReO3(η(2)-Tpm)(PTA)][ReO4] (4) [Tpm = hydrotris(pyrazol-1-yl)methane, HC(pz)3, pz = pyrazolyl], [ReO3(Hpz)(HMT)][ReO4] (5) (Hpz = pyrazole), [ReO(Tpms)(HMT)] (6) [Tpms = tris(pyrazol-1-yl)methanesulfonate, O3SC(pz)3(-)] and [ReCl2{N2C(O)Ph}(PTA)3] (7) have been prepared from the Re(VII) oxide Re2O7 (1-6) or, in the case of 7, by ligand exchange from the benzoyldiazenido complex [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2], and characterized by IR and NMR spectroscopies, elemental analysis and electrochemical properties. Theoretical calculations at the density functional theory (DFT) level of theory indicated that the coordination of PTA to both Re(III) and Re(VII) centers by the P atom is preferable compared to the coordination by the N atom. This is interpreted in terms of the Re-PTA bond energy and hard-soft acid-base theory. The oxo-rhenium complexes 1-6 act as selective catalysts for the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g., 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone, and 3,3-dimethyl-2-butanone or pinacolone) to the corresponding lactones or esters, in the presence of aqueous H2O2. The effects of a variety of factors are studied toward the optimization of the process.

The knowledge of photochemical kinetics in colloidal systems is important in understanding environmental photochemistry on dispersed solid surfaces. As model materials for the chemically sorbed organic compounds present in natural environments, modified silica nanoparticles (NPs) were obtained here by condensation of the silanol groups of fumed silica nanoparticles with 4-methoxybenzyl alcohol. These particles were characterized by different techniques. To evaluate their toxicity, the inhibition of the natural luminescence emission of the marine bacterium Vibrio fischeri in suspensions of the particles was measured. Laser flash-photolysis experiments (λexc = 266 nm) performed with NP suspensions in acetonitrile¿aqueous phosphate buffer mixtures showed the formation of the lowest triplet excited state of the chemisorbed organic groups (λmax = 390 nm). DFT calculations of the absorption spectrum of this radical support the assignment. From the calculated triplet energy, a thermodynamically favorable energy transfer from these triplet states to oxygen to yield singlet molecular oxygen is predicted. Avalue of 0.09 was measured for the quantum yield of singlet molecular oxygen generation by air-saturated suspensions of the nanoparticles in the mixture of solvents acetonitrile¿aqueous phosphate buffer. The quantum yield of singlet molecular oxygen generation by the free 4-methoxybenzyl alcohol in the same solvent is 0.31., The authors thank Dr F. C. Lovey and Dr A. Condo for the TEM experiments. Authors also want to acknowledge the financial support of Agencia Espanola de Cooperacion Internacional (project A/8199/07), Spanish Ministerio de Ciencia e Innovacion (EDARSOL project, CTQ 2009-13459-CO3-03), Universidad Politecnica de Valencia, and Agencia Nacional de Promocion Cientifica y Tecnologica (Argentina, project PICT 2008 # 0686). S. G. B., C.J.C. and M. C. G. are research members of CONICET, Argentina. D.O.M. is a research member of Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (Argentina).

The oxidation of alcohols to the corresponding carbonyl compounds is a pivotal reaction in organic synthesis. However, traditional oxidants are often toxic and release considerable amounts of by-products. As an alternative, oxygen (or even better air) is among the cheaper and less polluting stoichiometric oxidants, since it produces no waste or water as the sole by-product. The implementation of a transition metal-based catalyst in combination with oxygen represents an emerging alternative to the traditional procedures. This review aims to give an overview on the most important advances made by the scientific community in the last 15 years in the field of aerobic oxidations of alcohols catalyzed by transition metals in the form of homogeneous catalysts, heterogeneous catalysts and, more recently, nanoparticles.

A photocatalyst that may exhibit high activity for oxidation of volatile organic compounds (VOCs) under solar radiation would offer a practical and economic means for the cleaning of air under environmental conditions. We report here for the first time that the uranyl ions anchored within the mesopores of MCM-41 may serve as an efficient heterogeneous photocatalyst for the complete destruction of methanol in vapor phase, and in the presence of sunlight and air. The uranyl-anchored MCM-41 was found to be more efficient than a TiO2 photocatalyst in terms of CH3OH → CO2 conversion rates. The reversible and active participation of uranyl groups in the studied photocatalytic reaction was ascertained with the help of in situ fluorescence and electron paramagnetic resonance techniques, whereas the radiation-induced transient species over catalyst surface were monitored using in situ FTIR spectroscopy. The detailed reaction mechanism and the role played by uranyl ions in the photooxidation of methanol over U O 2 2 + /MCM are elucidated on the basis of these results.

The oxidative cleavage of the C=C double bond in unsaturated fatty acids into aldehydes or carboxylic acids is a reaction of current interest in biomass valorization. The products of this reaction, which is currently being performed on an industrial scale by means of ozonolysis, can be applied for the production of commodity chemicals such as plasticizers and polymers. Alternative, catalytic methods for this conversion that are not based on the hazardous ozone oxidant are of high interest. In this respect, the use of transition metal catalysts would allow the application of milder reaction conditions and more benign oxidants. This review covers the various transition metal-based catalysts that have been reported for the oxidative cleavage of alkenes in general and the cleavage of unsaturated fatty acids in particular. Catalytic systems based on second- and third-row metals such as Ru, Os, and W have been widely studied and are well-known to catalyze the cleavage of various alkenes and unsaturated fatty acids. In addition to simple metal salts, metal oxides or peroxides, various metal coordination complexes have been investigated for chemo- and regioselective olefin cleavage. Heterogeneous catalyst systems based on these metals have, in addition, been studied with a focus on catalyst reuse. To circumvent the use of expensive, toxic or less abundant second- and third-row metal catalysts, the use of first-row transition metal catalysts for the cleavage reaction might be preferred. However, examples of such catalysts for oxidative olefin cleavage are much less documented. The application of Fe- and Mn-based catalysts currently is largely limited to activated alkenes, e.g. styrene derivatives. The many possibilities that are offered by careful ligand design together with the recent advances in the field of first-row transition metal oxidation catalysis may allow for the development of catalyst systems that substitute ozone or second- and third-row metal catalysts for the oxidative cleavage of simple alkenes and unsaturated fatty acids.

A series of tetrabutylammonium (TBA) salts of the transition metal mono-substituted silicotungstates [SiW11M(H2O)O-39](n-), M = Co-II, Fe-III, Mn-III, (SiW11M) were explored as homogeneous catalysts for the oxidation of geraniol and styrene with H2O2. The most active homogeneous catalysts (SiW11Co and SiW11Fe) were immobilized onto an amine-functionalized SBA-15 (aptesSBA-15) and the resulting composites were characterized using several techniques (FT-IR, FT-Raman, UV-Vis/DRS, elemental analysis, powder XRD, SEM and N-2 adsorption-desorption isotherms). The catalytic performance of the new composites SiW11Co@aptesSBA-15 and SiW11Fe@aptesSBA-15 was investigated under similar experimental conditions to those used for homogeneous counterparts. 2,3-Epoxygeraniol and benzaldehyde were the main products obtained from geraniol and styrene oxidation, respectively, for all the catalysts. SiW11Co and SiW11Co@aptesSBA-15 showed to be the most active catalysts for the oxidation of geraniol and styrene. The recyclability of the composite SiW11Co@aptesSBA-15 was investigated for three reaction cycles. The stability of the composites was confirmed using several techniques after catalytic cycles.