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ispartof: ACS CATALYSIS vol:11 issue:17 pages:10862-10870 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.

A novel catalyst which carbon hybrid supported platinum nanoparticles were synthesized by our group for the oxidation of benzyl alcohol derivatives. In this study, this catalyst was utilized for the oxidation of benzyl alcohol derivatives to benzaldehyde compounds in aqueous toluene at 80 degrees C. The benzaldehyde derivatives were synthesized in high yields and mild conditions in the presence of the catalyst by the developed method. Additionally, the prepared nanoparticles have been characterized by Transmission Electron Microscopy (TEM), the high-resolution electron micrograph (HR-TEM), X-ray Photoelectron Spectroscopy (XPS), and X-ray Diffraction (XRD). The mean particle size of the nanoparticles determined by the XRD technique was found to be 2.83 nm in parallel with TEM analysis. TEM analysis also indicated that the Pt nanoparticles were evenly dispersed on the support material. Finally, the Pt@CHs catalyst was shown also stable and reusable for the oxidation reaction, providing

International audience; Manganese(III) acetate-mediated peroxycyclization between 2-hydroxy-3-methylnaphthoquinone and various alkenes was performed to obtain dihydronaphtho[2,3-c][1,2] dioxine-5,10(3H, 10aH)-diones. The reactivity of symmetrical or unsymmetrical 1,1-disubstituted alkenes and monosubstituted alkenes allowed the synthesis of more than 50 original molecules. Focusing on the excellent reactivity of 2-hydroxy-3-methylnaphthoquinone, we describe the first example of Mn(OAc)(3) reactivity with nitro-substituted alkenes. The scope, limitations and stereochemistry of the products synthesized are discussed. Starting from monosubstituted alkenes, the instability of a pair of diastereoisomers was observed, leading to ring opening.

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

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Graphene's sensitivity to adsorbed particles has attracted widespread attention because of its potential sensor applications. Size-selected few-atom clusters are promising candidates as adparticles to graphene. Due to their small size, physicochemical properties are dominated by quantum size effects. In particular, few-atom gold clusters demonstrate a significant catalytic activity in various oxidation reactions. In this joint experimental and computational work, size-selected gold clusters with 3 and 6 atoms adsorbed on graphene field-effect transistors and their interaction with molecular oxygen are investigated. While oxygen adsorbs at both cluster sizes, there is a pronounced cluster size dependence in the corresponding doping, as demonstrated via first-principle calculations and electronic transport measurements. Furthermore, the doping of gold cluster decorated graphene changes sign from n- to p-doping upon oxygen adsorption, directly evidencing electron transfer to the oxygen molecules and hence their activation. These observations pinpoint graphene as a valuable platform to investigate and exploit size-dependent cluster properties. ispartof: ADVANCED MATERIALS INTERFACES vol:5 issue:24 status: published

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.

Mononuclear discrete cobalt phosphonate [Co(pytpy)(tBuPO(3)H)(2)(H2O)]center dot H2O (1) and 1D zigzag polymeric cobalt phosphate [Co(pytpy)(2)(dipp)(MeOH)center dot 2MeOH](n) (2) were prepared from the reactions of tert-butyl phosphonic acid (tBuPO(3)H(2)) and organic-soluble 2,6-diisopropylphenyl phosphate (dippH(2)) ligands with Co(OAc)(2)center dot 4H(2)O in the presence of 4'-pyridyl 2,2':6',2 ''-terpyridine in MeOH/CHCl3(1:1 v/v) solvent mixture at 25 degrees C. The new compounds were characterized by analytical, thermo-analytical, and spectroscopic techniques. Further, the molecular structures were established by single-crystal X-ray diffraction studies. Mass spectrometry analysis reveal that both the compounds exist in the solution phase as dimers. Compound 1 was employed as homogeneous catalysts for alcohol oxidation reactions using tert-butyl hydroperoxide (TBHP) as the oxidant.

Reaction of [Pd(IPr)(2)] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and O-2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)(2)(eta(2)-O-2)]. At temperatures greater than or similar to -40 degrees C, cis-[Pd(IPr)(2)(eta(2)-O-2)] adds a second O-2 to form trans-[Pd(IPr)(2)(eta(1)-O-2)(2)]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O-2 , cis-[Pd(IPr)(2)(eta(2)-O-2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)(2)(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)(2)(OOH) (OH)] is reported. Neither reaction with O-2 nor reaction with H2O occurs under comparable conditions for cis-[Pd(IMes)(2)(eta(2)-O-2)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)(2)(eta(2)-O-2)] is attributed to the enthalpy of binding of O-2 to [Pd(IPr)(2)] (-14.5 +/- 1.0 kcal/mol) that is approximately one-half that of [Pd(IMes)(2)] (-27.9 +/- 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)(2)(eta(2)-O-2)]. Arene-arene interactions are more favorable and serve to further stabilize. cis-[Pd(IMes)(2)(eta(2)-O-2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O-2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)(2)(eta(1)-O-2)(2)] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)(2)(eta(1)-O-2)(2)] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)(2)(eta(1)-O-2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O-2 is constructed. A range of low-energy pathways at different angles of approach are present and blur the distinction between pure "side-on" or "end-on" trajectories for oxygen binding.

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.

Reports on aerobic oxidation of amines to amides are rare, and those reported suffer from several limitations like poor yield or selectivity and make use of pure oxygen under elevated pressure. Herein, we report a practical and an efficient ruthenium-catalyzed synthetic protocol that enables selective oxidation of a broad range of primary aliphatic, heterocyclic and benzylic amines to their corresponding amides, using readily available reagents and ambient air as the sole oxidant. Secondary amines instead, yield benzamides selectively as the sole product. Mechanistic investigations reveal intermediacy of nitriles, which undergo hydration to afford amide as the final product.

A ligand controlled catalytic system for the aerobic oxidation of 1° amines to nitriles and imines has been developed where the varying π-acidic feature of BIAN versus phen in the frameworks of ruthenium catalysts facilitates switchable selectivity.

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.

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.

A cascade reaction, consisting of a palladium-catalyzed regioselective aerobic oxidative carbocyclization-borylation of bisallenes and a final aldehyde trapping, afforded triene alcohols with high diastereoselectivity. The cascade reaction occurs under mild reaction conditions and proceeds via an allylboron intermediate that is trapped by the aldehyde in a stereoselective manner.

© 2018 The Royal Society of Chemistry. Molecular oxygen is without doubt the greenest oxidant for redox reactions, yet aerobic oxidation is one of the most challenging to perform with good chemoselectivity, particularly on an industrial scale. This collaborative review (between teams of chemists and chemical engineers) describes the current scientific and operational hurdles that prevent the utilisation of aerobic oxidation reactions for the production of speciality chemicals and active pharmaceutical ingredients (APIs). The safety aspects of these reactions are discussed, followed by an overview of (continuous flow) reactors suitable for aerobic oxidation reactions that can be applied on scale. Some examples of how these reactions are currently performed in the industrial laboratory (in batch and in flow) are presented, with particular focus on the scale-up strategy. Last but not least, further challenges and future perspectives are presented in the concluding remarks. crosscheck: This document is CrossCheck deposited identifier: Simon Kuhn (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 30 August 2016; Accepted 13 September 2016; Advance Article published 22 September 2016; Version of Record published 22 November 2016 ispartof: Reaction Chemistry & Engineering vol:1 issue:6 pages:595-612 status: published

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Thiols are smoothly and efficiently oxidized to disulfides (RSSR) with air in the presence of gold nanoparticles supported on CeO2 in absence of solvent, as well as in aqueous solutions and neutral pH. It is shown that the reaction can occur through the coupling of two sulphur radicals on the metal surface. The sulphur radicals are formed from thiols by one-electron oxidation with the metal. This reaction mechanism strongly resembles that found for sulfhydryl oxidases, a class of enzymes which are involved in the oxidative protein folding through de novo formation of disulfides from thiols., lFinancial support by Consolider-Ingenio 2010 (project MULTICAT), Spanish MICINN (Projects MAT2006-14274-C02-01 and MAT2011-28009), Generalitat Valenciana (Project PROMETEO/2008/130) and Fundacion Areces are gratefully acknowledged. T.R. expresses her gratitude to Consejo Superior de Investigaciones Cientificas for an I3-P fellowship.

Nitrogen and sulfur co-doping has been achieved in the commercial TiO 2 nanoparticles of anatase TKP 102 (Tayca) by grinding it with thiourea and calcinating at 400 °C. The successful substitutional N-doping and cationic/anionic S-doping were validated by XPS measurements. Diffuse reflectance spectroscopy (DRS) showed a marked broadening of the absorption spectrum of the doped material towards the visible range. Phenol and dichloroacetate (DCA) oxidation and Escherichia coli inactivation were achieved under UV illumination using the N, S co-doped TiO 2 powders. Electron spin resonance (ESR) spin-trapping experiments showed that under UV light irradiation, the OH radicals were the main species responsible for photo-degradation of phenol and E. coli abatement. Photo-degradation of DCA was found to be due a direct interaction of the TiO 2 valence band holes ( h VB + ) with the DCA molecules. Moreover, under visible light (400–500 nm) illumination of N, S co-doped TiO 2 a complete inactivation of E. coli bacteria was observed. In contrast, under such conditions, phenol was only partially degraded, whereas DCA was not at all affected. ESR experiments performed with N, S co-doped TiO 2 powders illuminated with visible light and in the presence of singlet oxygen ( 1 O 2 ) quencher, TMP-OH, showed the formation of 1 O 2 . This suggests that superoxide radical ( O 2 − ) and its oxidation product, 1 O 2 , were responsible for E. coli inactivation by N, S co-doped TiO 2 nanoparticles under visible light.

On the basis of experimental evidence and DFT calculations, we propose a simple yet viable way to stabilize and chemically activate gold nanoclusters on MgO. First the MgO surface is functionalized by creation of trapped electrons, (H+)(e-) centers (exposure to atomic H or to H2 under UV light, deposition of low amounts of alkali metals on partially hydroxylated surfaces, etc.); the second step consists in the self-aggregation of gold clusters deposited from the gas phase. The calculations show that the (H+)(e-) centers act both as nucleation and activation sites. The process can lead to thermally stable gold cluster anions whose catalytic activity is enhanced by the presence of an excess electron. © 2008 American Chemical Society.

Catalytic activity of perovskites for oxygen reduction (ORR) was recently correlated with bulk d-electron occupancy of the transition metal. We expand on the resultant model, which successfully reproduces the high activity of LaMnO3 relative to other perovskites, by addressing catalyst surface morphology as an important aspect of the optimal ORR catalyst. The nature of reaction sites on low index surfaces of orthorhombic (Pnma) LaMnO3 is established from First Principles. The adsorption of O2 is markedly influenced by local geometry and strong electron correlation. Only one of the six reactions sites that result from experimentally confirmed symmetry-breaking Jahn-Teller distortions is found to bind O2 with an intermediate binding energy while facilitating the formation of superoxide, an important ORR intermediate in alkaline media. As demonstrated here for LaMnO3, rational design of the catalyst morphology to promote specific active sites is a highly effective optimization strategy for advanced functional ORR catalysts. © 2015 American Chemical Society.

Since the discovery of Metal Organic Frameworks (MOFs) in the early 1990s, the amount of new structures has grown exponentially. A MOF typically consists of inorganic nodes that are connected by organic linkers to form crystalline, highly porous structures. MOFs have attracted a lot of attention lately, as the versatile design of such materials holds promises of interesting applications in various fields. In this review, we will focus on the use of MOFs as heterogeneous oxidation catalysts. MOFs are very promising candidates to replace homogeneous catalysts by sustainable and stable heterogeneous catalysts. The catalytic active function can be either the active metal sites of the MOF itself or can be introduced as an extra functionality in the linker, a dopant or a "ship-in-a-bottle" complex. As the pore size, pore shape, and functionality of MOFs can be designed in numerous ways, shape selectivity, and even chiral selectivity can be created. In this article, we will present an overview on the state of the art of the use of MOFs as a heterogeneous catalyst in liquid phase oxidation reactions.

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 oxovanadium(IV) complexes [VO(acac)2(Hpz)]·HC(pz)3 1·HC(pz)3 (acac = acetylacetonate, Hpz = pyrazole, pz = pyrazolyl) and [VOCl2{HOCH2C(pz)3}] 2 were obtained from reaction of [VO(acac)2] with hydrotris(1-pyrazolyl)methane or of VCl3with 2,2,2-tris(1-pyrazolyl)ethanol. The compounds were characterized by elemental analysis, IR, Far-IR and EPR spectroscopies, FAB or ESI mass-spectrometry and, for 1, by single crystal X-ray diffraction analysis. 1 and 2 exhibit catalytic activity for the oxidation of cyclohexane to the cyclohexanol and cyclohexanone mixture in homogeneous system (TONs up to 1100) under mild conditions (NCMe, 24 h, room temperature) using benzoyl peroxide (BPO), tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (mCPBA), hydrogen peroxide or the urea-hydrogen peroxide adduct (UHP) as oxidants. 1 and 2 were also immobilized on a polydimethylsiloxane membrane (1-PDMS or 2-PDMS) and the systems acted as supported catalysts for the cyclohexane oxidation using the above oxidants (TONs up to 620). The best results were obtained with mCPBA or BPO as oxidant. The effects of various parameters, such as the amount of catalyst, nitric acid, reaction time, type of oxidant and oxidant-to-catalyst molar ratio, were investigated, for both homogeneous and supported systems.

a b s t r a c t Periodic density functional theory (DFT) calculations have been used to study the effect of doping a gold model surface with atoms of other transition metals on the catalysis of the reaction of oxygen dissociation. It was found that the doping of gold surfaces with atoms of Rh, Ir or Ni stabilizes the adsorbate-surface interactions with a concomitant decrease of the activation energy barriers for the oxygen dissociation to values that are smaller than the adsorption energies of molecular oxygen (O2*) on those surfaces. These findings suggest that O2 dissociation is possible at normal conditions on these bimetallic surfaces, which is very relevant not only for the oxidation of CO to CO2 but for other oxidation reactions. In the case of the most active bimetallic surface obtained by doping with Ni atoms, it is shown that the reaction of CO oxidation is more favorable than the reaction of CO dissociation, i.e., suggesting that CO methanation will be less likely. Finally, useful relationships relating the activation energy barrier for the reaction of O2 dissociation with the Bader charge in the doping element, with the reaction energy, with the adsorption energy of the reaction products and with the adsorption energy of an oxygen atom were obtained. © 2013 Elsevier B.V. All rights reserved.

Two new 3D metal-organic frameworks (MOF), [Co(H-2-DHBDA)(bpe)](n) (1) and [Co(H-2-DHBDA)(bpee)](n) (2) [H-2-DHBDA = 2,5-dihydroxy-1,4-benzenediacetate, bpe = 1,2-bis(4-pyridyl)ethylene, bpee = 1,2-bis(4-pyridyl)ethane], were synthesized hydrothermally. Both compounds have a similar 3D structure. The secondary building unit is a Co-2 dimer with a CoCo distance of 4.02 angstrom. The hydroxy groups remain free on the surface of the compounds, and they participate in the intramolecular hydrogen bonding. A detailed structural analysis revealed that the structure is a 7-c uninodal net with the Schlafli symbol 3(3).4(13).5(4).6 and the vertex symbol [3.3.3.4.4.4.4.4.4.4.4.4.4.4.4.*.*.*.*.*.*]. The compound is catalytically active towards epoxidation reactions in heterogeneous medium with H2O2 as an oxidant. They catalyze the epoxidation of almost all types of olefinic substrates with good efficiency. After the reaction, the catalysts can be recovered quite easily, and they can be used for further reactions without any loss of activity for several cycles.

A new phosphonate-based metal organic framework has been synthesized. The structure determined by X-ray crystallography reveals that it has an interesting 8-ring channel 3D structure having the Co-2-dimers as the secondary building unit. Topological analysis shows that it has 10-c uninodal 3D net structure with the Schlafli symbol 3(15).4(22).5(8). The magnetic measurement reveals the tetrahedral coordinated Co-II ion. The compound is highly active towards epoxidation in the presence of air and IBA (isobutyraldehyde). It catalyses almost all types of olefinic substrates with equal efficiency. The compound is highly stable thermally (370 degrees C) and under the reaction conditions as well. After the reaction it can be recovered quite easily and can be used for further reaction without any loss of activity over several cycles.

A general method for selective dehydroxymethylation has been discovered by using widely available Pd(OAc)(2). The present study offers a new synthetic strategy for the regioselective functionalization by employing the steric, electronic and coordinating nature of the hydroxymethyl (-CH(2)OH) group temporarily.

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.

Carbohydrate-decorated meso-tetraarylporphyrins P-G and P-C were synthesized via Lewis-acid catalyzed condensation of acetylated carbohydrate-substituted benzaldehydes and pyrrole. Their efficiency of singlet oxygen production was compared with the corresponding non-substituted porphyrin. The oxidation of the spin trap molecule TEMP (2,2,6,6-tetramethyl-4-piperidone) by singlet oxygen to TEMPO was measured by ESR spectroscopy, showing higher reaction rates for the sugar porphyrins. These results were corroborate by laser flash photolysis measurements that resulted in higher triplet lifetimes of glucosyl-and cellobiosyl porphyrins in comparison with tetrakis(4-hydroxyphenyl) porphyrin. Low ee was detected in the photooxygenation of ethyl tiglate., The financial support by the Deutsche Forschungsgemeinschaft (DFG) is acknowledged. J.U. thanks the Alder foundation for a half-year research stay in Valencia.

The rate of oxidation and the catalyst stability in the oxidation of 1-alkenes with O2 using [PdCl(NO2)(MeCN)2] as catalyst is considerably improved by the use of amides as ligands or solvents.

A new method for the synthesis of beta(3)-amino acids is presented. Phthalimide protected allylic amines are oxidized under Wacker conditions selectively to aldehydes using PdCl(2) and CuCl or Pd(MeCN)(2)Cl(NO(2)) and CuCl(2) as complementary catalyst systems. The aldehydes are produced in excellent yields and exhibit a large substrate scope. Beta-amino acids and alcohols are synthesized by oxidation or reduction and subsequent deprotection.

The photophysical and spectroscopic characterization of four new dimeric bis(BF2)-2,2 '-bidipyrrins (BisBODIPYs) recently synthesized and characterized (Chem. Eur. J., 2008, 14, 2976-2983) has been undertaken along with that of the component BODIPY monomers. The monomers display the typical photophysical properties of this family; (i) narrow and intense single absorption band in the visible range at 530 nm; (ii) intense, solvent independent emission (Phi(fl) ca. 1); (iii) narrow emission band with a 200-400 cm(-1) Stokes shifted emission, independent of solvent polarity; (iv) no absorption features for the singlet excited state; (v) very little triplet yield and no ability to sensitize singlet oxygen. The absorption spectra of the corresponding new dimers exhibit split band maxima in the visible range at about 490 and 560 nm, corresponding to an exciton splitting of ca. 2600 cm(-1). The luminescence in toluene is strong (Phi(fl) ca. 0.7, tau = 3.4 ns), broad and Stokes shifted by ca. 2200 cm(-1), but both luminescence yield and Stokes shift are solvent polarity dependent; F. < 0.1, tau < 1 ns and the Stokes shift is close to 2700 cm(-1) in acetonitrile. Solvent viscosity does not appear to play an important role and freezing of the solvents to 77 K in a solid matrix cancels the differences in luminescence parameters. Singlet and triplet excited state absorbance was measured in toluene and acetonitrile and the ability of these new dyes to sensitize singlet oxygen was examined. The nature and dynamics of the excited state is discussed in comparison with the monomers properties and with some intra- or inter-molecular BODIPY dimers reported in the literature. Potential applications of these new dyes with respect to BODIPYs are pointed out on the basis of their spectroscopic and photophysical properties.

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.

An overview of asymmetric transformations induced by photochemical means in the presence of a substoichiometric amount of external chiral reagent is presented. The main obstacles in achieving asymmetric induction catalytically, and successful examples of ways to overcome these hurdles are discussed.

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.